document_title: Air conditioning

question_text: when was central air conditioning invented for homes

question_tokens: when was central air conditioning invented for homes

text: Air conditioning

text: History[edit]

text: Evaporative cooling[edit]

text: Since prehistoric times, snow and ice were used for cooling. The business of harvesting ice during winter and storing for use in summer became popular towards the late 17th century.[3] This practice was replaced by mechanical ice-making machines.

text: The basic concept behind air conditioning is said to have been applied in ancient Egypt, where reeds were hung in windows and were moistened with trickling water. The evaporation of water cooled the air blowing through the window. This process also made the air more humid, which can be beneficial in a dry desert climate. In Ancient Rome, water from aqueducts was circulated through the walls of certain houses to cool them. Other techniques in medieval Persia involved the use of cisterns and wind towers to cool buildings during the hot season.[4]

text: The 2nd-century Chinese mechanical engineer and inventor Ding Huan of the Han Dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered by prisoners of the time.[5] In 747, Emperor Xuanzong (r. 712–762) of the Tang Dynasty (618–907) had the Cool Hall (Liang Tian) built in the imperial palace, which the Tang Yulin describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song Dynasty (960–1279), written sources mentioned the air conditioning rotary fan as even more widely used.[6]

text: In the 17th century, the Dutch inventor Cornelis Drebbel demonstrated "Turning Summer into Winter" as an early form of modern air conditioning for James I of England by adding salt to water.[7]

text: Development of mechanical cooling[edit]

text: Modern air conditioning emerged from advances in chemistry during the 19th century, and the first large-scale electrical air conditioning was invented and used in 1902 by American inventor Willis Carrier. The introduction of residential air conditioning in the 1920s helped enable the great migration to the Sun Belt in the United States.[citation needed]

text: In 1758, Benjamin Franklin and John Hadley, a chemistry professor at Cambridge University, conducted an experiment to explore the principle of evaporation as a means to rapidly cool an object. Franklin and Hadley confirmed that evaporation of highly volatile liquids (such as alcohol and ether) could be used to drive down the temperature of an object past the freezing point of water. They conducted their experiment with the bulb of a mercury thermometer as their object and with a bellows used to speed up the evaporation. They lowered the temperature of the thermometer bulb down to −14 °C (7 °F) while the ambient temperature was 18 °C (64 °F). Franklin noted that, soon after they passed the freezing point of water 0 °C (32 °F), a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about 6 mm (1⁄4 in) thick when they stopped the experiment upon reaching −14 °C (7 °F). Franklin concluded: "From this experiment one may see the possibility of freezing a man to death on a warm summer's day"[8]

text: In 1820, English scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate. In 1842, Florida physician John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital in Apalachicola, Florida. He hoped to eventually use his ice-making machine to regulate the temperature of buildings. He even envisioned centralized air conditioning that could cool entire cities. Though his prototype leaked and performed irregularly, Gorrie was granted a patent in 1851 for his ice-making machine. Though his process improved the artificial production of ice, his hopes for its success vanished soon afterwards when his chief financial backer died and Gorrie did not get the money he needed to develop the machine. According to his biographer, Vivian M. Sherlock, he blamed the "Ice King", Frederic Tudor, for his failure, suspecting that Tudor had launched a smear campaign against his invention. Dr. Gorrie died impoverished in 1855, and the dream of commonplace air conditioning went away for 50 years.[citation needed]

text: James Harrison's first mechanical ice-making machine began operation in 1851 on the banks of the Barwon River at Rocky Point in Geelong (Australia). His first commercial ice-making machine followed in 1853, and his patent for an ether vapor compression refrigeration system was granted in 1855. This novel system used a compressor to force the refrigeration gas to pass through a condenser, where it cooled down and liquefied. The liquefied gas then circulated through the refrigeration coils and vaporized again, cooling down the surrounding system. The machine produced 3,000 kilograms of ice per day.[citation needed]

text: Though Harrison had commercial success establishing a second ice company back in Sydney in 1860, he later entered the debate over how to compete against the American advantage of ice refrigerated beef sales to the United Kingdom. He wrote: "Fresh meat frozen and packed as if for a voyage, so that the refrigerating process may be continued for any required period", and in 1873 prepared the sailing ship Norfolk for an experimental beef shipment to the United Kingdom. His choice of a cold room system instead of installing a refrigeration system upon the ship itself proved disastrous when the ice was consumed faster than expected.[citation needed]

text: Electromechanical cooling[edit]

text: In 1902, the first modern electrical air conditioning unit was invented by Willis Carrier in Buffalo, New York. After graduating from Cornell University, Carrier found a job at the Buffalo Forge Company. While there, he began experimenting with air conditioning as a way to solve an application problem for the Sackett-Wilhelms Lithographing and Publishing Company in Brooklyn, New York. The first air conditioner, designed and built in Buffalo by Carrier, began working on 17 July 1902.[citation needed]

text: Designed to improve manufacturing process control in a printing plant, Carrier's invention controlled not only temperature but also humidity. Carrier used his knowledge of the heating of objects with steam and reversed the process. Instead of sending air through hot coils, he sent it through cold coils (filled with cold water). The air was cooled, and thereby the amount of moisture in the air could be controlled, which in turn made the humidity in the room controllable. The controlled temperature and humidity helped maintain consistent paper dimensions and ink alignment. Later, Carrier's technology was applied to increase productivity in the workplace, and The Carrier Air Conditioning Company of America was formed to meet rising demand. Over time, air conditioning came to be used to improve comfort in homes and automobiles as well. Residential sales expanded dramatically in the 1950s.[citation needed]

text: In 1906, Stuart W. Cramer of Charlotte was exploring ways to add moisture to the air in his textile mill. Cramer coined the term "air conditioning", using it in a patent claim he filed that year as an analogue to "water conditioning", then a well-known process for making textiles easier to process. He combined moisture with ventilation to "condition" and change the air in the factories, controlling the humidity so necessary in textile plants. Willis Carrier adopted the term and incorporated it into the name of his company.[9]

text: Shortly thereafter, the first private home to have air conditioning was built in Minneapolis in 1914, owned by Charles Gates.[10] Realizing that air conditioning would one day be a standard feature of private homes, particularly in regions with warmer climate, David St. Pierre DuBose (1898-1994) designed a network of ductwork and vents for his home Meadowmont, all disguised behind intricate and attractive Georgian-style open moldings.[when?] This building is believed to be one of the first private homes in the United States equipped for central air conditioning.[11]

text: In 1945, Robert Sherman of Lynn, Massachusetts invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air.[12]

text: Refrigerant development[edit]

text: The first air conditioners and refrigerators employed toxic or flammable gases, such as ammonia, methyl chloride, or propane, that could result in fatal accidents when they leaked. Thomas Midgley, Jr. created the first non-flammable, non-toxic chlorofluorocarbon gas, Freon, in 1928. The name is a trademark name owned by DuPont for any chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), or hydrofluorocarbon (HFC) refrigerant. The refrigerant names include a number indicating the molecular composition (e.g., R-11, R-12, R-22, R-134A). The blend most used in direct-expansion home and building comfort cooling is an HCFC known as chlorodifluoromethane (R-22).

text: Dichlorodifluoromethane (R-12) was the most common blend used in automobiles in the US until 1994, when most designs changed to R-134A due to the ozone-depleting potential of R-12. R-11 and R-12 are no longer manufactured in the US for this type of application, so the only source for air-conditioning repair purposes is the cleaned and purified gas recovered from other air conditioner systems. Several non-ozone-depleting refrigerants have been developed as alternatives, including R-410A. It was first commercially used by Carrier Corp. under the brand name Puron.[citation needed]

text: Modern refrigerants have been developed to be more environmentally safe than many of the early chlorofluorocarbon-based refrigerants used in the early- and mid-twentieth century. These include HCFCs (R-22, as used in most U.S. homes even before 2011) and HFCs (R-134a, used in most cars) have replaced most CFC use. HCFCs, in turn, are supposed to have been in the process of being phased out under the Montreal Protocol and replaced by HFCs such as R-410A, which lack chlorine.[13] HFCs, however, contribute to climate change problems. Moreover, policy and political influence by corporate executives resisted change.[14][15] Corporations insisted that no alternatives to HFCs existed. The environmental organization Greenpeace solicited a European laboratory to research an alternative ozone- and climate-safe refrigerant in 1992, gained patent rights to a hydrocarbon mix of isopentane and isobutane, but then left the technology as open access.[16][17] Their activist marketing first in Germany led to companies like Whirlpool, Bosch, and later LG and others to incorporate the technology throughout Europe, then Asia, although the corporate executives resisted in Latin America, so that it arrived in Argentina produced by a domestic firm in 2003, and then finally with giant Bosch's production in Brazil by 2004.[18][19]

text: In 1995, Germany made CFC refrigerators illegal.[20] DuPont and other companies blocked the refrigerant in the U.S. with the U.S. E.P.A., disparaging the approach as "that German technology."[19][21] Nevertheless, in 2004, Greenpeace worked with multinational corporations like Coca-Cola and Unilever, and later Pepsico and others, to create a corporate coalition called Refrigerants Naturally!.[20][22] Then, four years later, Ben & Jerry's of Unilever and General Electric began to take steps to support production and use in the U.S.[23] Only in 2011 did the E.P.A. finally decide in favor of the ozone- and climate-safe refrigerant for U.S. manufacture.[16][24][25]

text: Operating principles[edit]

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text: Refrigeration cycle[edit]

text: In the refrigeration cycle, heat is transported from a colder location to a hotter area. As heat would naturally flow in the opposite direction, work is required to achieve this. A refrigerator is an example of such a system, as it transports the heat out of the interior and into its environment. The refrigerant is used as the medium which absorbs and removes heat from the space to be cooled and subsequently ejects that heat elsewhere.

text: Circulating refrigerant vapor enters the compressor, where its pressure and temperature are increased. The hot, compressed refrigerant vapor is now at a temperature and pressure at which it can be condensed and is routed through a condenser. Here it is cooled by air flowing across the condenser coils and condensed into a liquid. Thus, the circulating refrigerant removes heat from the system and the heat is carried away by the air. The removal of this heat can be greatly augmented by pouring water over the condenser coils, making it much cooler when it hits the expansion valve.

text: The condensed, pressurized, and still usually somewhat hot liquid refrigerant is next routed through an expansion valve (often nothing more than a pinhole in the system's copper tubing) where it undergoes an abrupt reduction in pressure. That pressure reduction results in flash evaporation of a part of the liquid refrigerant, greatly lowering its temperature. Aircraft air conditioners use turbines for cooling, more efficient but more complex. The cold refrigerant is then routed through the evaporator. A fan blows the interior warm air (which is to be cooled) across the evaporator, causing the liquid part of the cold refrigerant mixture to evaporate as well, further lowering the temperature. The warm air is therefore cooled and is pumped by an exhaust fan/ blower into the room. To complete the refrigeration cycle, the refrigerant vapor is routed back into the compressor. In order for the process to have any efficiency, the cooling/evaporative portion of the system must be separated by some kind of physical barrier from the heating/condensing portion, and each portion must have its own fan to circulate its own "kind" of air (either the hot air or the cool air).

text: Modern air conditioning systems are not designed to draw air into the room from the outside, they only recirculate the increasingly cool air on the inside. Because this inside air always has some amount of moisture suspended in it, the cooling portion of the process always causes ambient warm water vapor to condense on the cooling coils and to drip from them down onto a catch tray at the bottom of the unit from which it must then be routed outside, usually through a drain hole. As this moisture has no dissolved minerals in it, it will not cause mineral buildup on the coils. This will happen even if the ambient humidity level is low. If ice begins to form on the evaporative fins, it will reduce circulation efficiency and cause the development of more ice, etc. A clean and strong circulatory fan can help prevent this, as will raising the target cool temperature of the unit's thermostat to a point that the compressor is allowed to turn off occasionally. A failing thermistor may also cause this problem. Refrigerators without a defrost cycle may have this same issue. Dust can also cause the fins to begin blocking air flow with the same undesirable result: ice.

text: By running an air conditioner's compressor in the opposite direction, the overall effect can be completely reversed and the indoor compartment will become heated instead of cooled (see heat pump). The engineering of physical and thermodynamic properties of gas–vapor mixtures is called psychrometrics.

text: Heat pump unit[edit]

text: A heat pump is an air conditioner in which the refrigeration cycle can be reversed, producing heating instead of cooling in the indoor environment. They are also commonly referred to as a "reverse cycle air conditioner". The heat pump is significantly more energy efficient than electric resistance heating. Some homeowners elect to have a heat pump system installed as a feature of a central air conditioner. When the heat pump is in heating mode, the indoor evaporator coil switches roles and becomes the condenser coil, producing heat. The outdoor condenser unit also switches roles to serve as the evaporator, and discharges cold air (colder than the ambient outdoor air).

text: Air-source heat pumps are more popular in milder winter climates where the temperature is frequently in the range of 40–55 °F (4–13 °C), because heat pumps become inefficient in more extreme cold. This is because ice forms on the outdoor unit's heat exchanger coil, which blocks air flow over the coil. To compensate for this, the heat pump system must temporarily switch back into the regular air conditioning mode to switch the outdoor evaporator coil back to being the condenser coil, so that it can heat up and defrost. A heat pump system will therefore have a form of electric resistance heating in the indoor air path that is activated only in this mode in order to compensate for the temporary indoor air cooling, which would otherwise be uncomfortable in the winter.

text: The icing problem becomes much more severe with lower outdoor temperatures, so heat pumps are commonly installed in tandem with a more conventional form of heating, such as a natural gas or oil furnace, which is used instead of the heat pump during harsher winter temperatures. In this case, the heat pump is used efficiently during the milder temperatures, and the system is switched to the conventional heat source when the outdoor temperature is lower.

text: Absorption heat pumps are a kind of air-source heat pump, but they do not depend on electricity to power them. Instead, gas, solar power, or heated water is used as a main power source. An absorption pump dissolves ammonia gas in water, which gives off heat. Next, the water and ammonia mixture is depressurized to induce boiling, and the ammonia is boiled off, which absorbs heat from the outdoor air.[citation needed]

text: Some more expensive fixed window air conditioning units have a true heat pump function. However, a window unit may only have an electric resistance heater.

text: Evaporative cooling[edit]

text: In very dry climates, evaporative coolers, sometimes referred to as swamp coolers or desert coolers, are popular for improving coolness during hot weather. An evaporative cooler is a device that draws outside air through a wet pad, such as a large sponge soaked with water. The sensible heat of the incoming air, as measured by a dry bulb thermometer, is reduced. The temperature of the incoming air is reduced, but it is also more humid, so the total heat (sensible heat plus latent heat) is unchanged. Some of the sensible heat of the entering air is converted to latent heat by the evaporation of water in the wet cooler pads. If the entering air is dry enough, the results can be quite substantial.

text: Evaporative coolers tend to feel as if they are not working during times of high humidity, when there is not much dry air with which the coolers can work to make the air as cool as possible for dwelling occupants. Unlike other types of air conditioners, evaporative coolers rely on the outside air to be channeled through cooler pads that cool the air before it reaches the inside of a house through its air duct system; this cooled outside air must be allowed to push the warmer air within the house out through an exhaust opening such as an open door or window.[26] These coolers cost less and are mechanically simple to understand and maintain.

text: Free cooling[edit]

text: Air conditioning can also be provided by a process called free cooling which uses pumps to circulate a coolant (typically water or a glycol mix) from a cold source, which in turn acts as a heat sink for the energy that is removed from the cooled space. Common storage media are deep aquifers or a natural underground rock mass accessed via a cluster of small-diameter boreholes, equipped with heat exchanger. Some systems with small storage capacity are hybrid systems, using free cooling early in the cooling season, and later employing a heat pump to chill the circulation coming from the storage. The heat pump is added because the temperature of the storage gradually increases during the cooling season, thereby declining its effectiveness.

text: Free cooling systems can have very high efficiencies, and are sometimes combined with seasonal thermal energy storage (STES) so the cold of winter can be used for summer air conditioning. Free cooling and hybrid systems are mature technology.[27]

text: Humidity control[edit]

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text: Since humans perspire to provide natural cooling by the evaporation of perspiration from the skin, drier air (up to a point) improves the comfort provided. The comfort air conditioner is designed to create a 50% to 60% relative humidity in the occupied space.[citation needed]

text: Dehumidification and cooling[edit]

text: Refrigeration air conditioning equipment usually reduces the absolute humidity of the air processed by the system. The relatively cold (below the dewpoint) evaporator coil condenses water vapor from the processed air, much like an ice-cold drink will condense water on the outside of a glass. Therefore, water vapor is removed from the cooled air and the relative humidity in the room is lowered. The water is usually sent to a drain or may simply drip onto the ground outdoors. The heat is rejected by the condenser which is located outside of room to be cooled.

text: Dehumidification Program[edit]

text: On most modern Air-conditioning systems there is a dehumidification cycle; the compressor is on and the fan is slowed as much as possible (lowest speed under normal conditions).[citation needed] This reduces the evaporator temperature and therefore condenses more water than if it were to have a high fan speed. To help mitigate temperature drops when the temperature falls below a threshold, both the fan and compressor turn off,[clarification needed] this stops moisture on the evaporator being blown back into the room.[citation needed] When the temperature rises[clarification needed] again the compressor comes and and the fan goes back to low speed. However occasionally the fan will stay on and compressor go off to thaw any ice produced (hence why the program doesn't work in cool conditions).

text: Inverter type Air Conditioners use the inside coil temperature sensor (typically used for heat pump operation where it regulates fan speed according to how warm the evaporator is) to adjust compressor speed to keep the evaporator as cold as possible, when the evaporator is too cold[clarification needed] the compressor is slowed or stopped with the indoor fan running.

text: Dehumidifier[edit]

text: A specialized air conditioner that is used only for dehumidifying is called a dehumidifier. It also uses a refrigeration cycle, but differs from a standard air conditioner in that both the evaporator and the condenser are placed in the same air path. A standard air conditioner transfers heat energy out of the room because its condenser coil releases heat outside. However, since all components of the dehumidifier are in the same room, no heat energy is removed. Instead, the electric power consumed by the dehumidifier remains in the room as heat, so the room is actually heated, just as by an electric heater that draws the same amount of power.

text: In addition, if water is condensed in the room, the amount of heat previously needed to evaporate that water also is re-released in the room (the latent heat of vaporization). The dehumidification process is the inverse of adding water to the room with an evaporative cooler, and instead releases heat. Therefore, an in-room dehumidifier always will warm the room and reduce the relative humidity indirectly, as well as reducing the humidity directly by condensing and removing water.

text: Inside the unit, the air passes over the evaporator coil first, and is cooled and dehumidified. The now dehumidified, cold air then passes over the condenser coil where it is warmed up again. Then the air is released back into the room. The unit produces warm, dehumidified air and can usually be placed freely in the environment (room) that is to be conditioned.

text: Dehumidifiers are commonly used in cold, damp climates to prevent mold growth indoors, especially in basements. They are also used to protect sensitive equipment from the adverse effects of excessive humidity in tropical countries.

text: Energy transfer[edit]

text: In a thermodynamically closed system, any power dissipated into the system that is being maintained at a set temperature (which is a standard mode of operation for modern air conditioners) requires that the rate of energy removal by the air conditioner increase. This increase has the effect that, for each unit of energy input into the system (say to power a light bulb in the closed system), the air conditioner removes that energy.[28] In order to do so, the air conditioner must increase its power consumption by the inverse of its "efficiency" (coefficient of performance) times the amount of power dissipated into the system. As an example, assume that inside the closed system a 100 W heating element is activated, and the air conditioner has an coefficient of performance of 200%. The air conditioner's power consumption will increase by 50 W to compensate for this, thus making the 100 W heating element cost a total of 150 W of power.

text: It is typical for air conditioners to operate at "efficiencies" of significantly greater than 100%.[29] However, it may be noted that the input electrical energy is of higher thermodynamic quality (lower entropy) than the output thermal energy (heat energy).

text: Air conditioner equipment power in the U.S. is often described in terms of "tons of refrigeration". A ton of refrigeration is approximately equal to the cooling power of one short ton (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. The value is defined as 12,000 BTU per hour, or 3517 watts.[30] Residential central air systems are usually from 1 to 5 tons (3 to 20 kilowatts (kW)) in capacity.

text: Seasonal energy efficiency ratio[edit]

text: For residential homes, some countries set minimum requirements for energy efficiency. In the United States, the efficiency of air conditioners is often (but not always) rated by the seasonal energy efficiency ratio (SEER). The higher the SEER rating, the more energy efficient is the air conditioner. The SEER rating is the BTU of cooling output during its normal annual usage divided by the total electric energy input in watt hours (W·h) during the same period.[31]

text: this can also be rewritten as:

text: For example, a 5000 BTU/h air-conditioning unit, with a SEER of 10, would consume 5000/10 = 500 Watts of power on average.

text: The electrical energy consumed per year can be calculated as the average power multiplied by the annual operating time:

text: Assuming 1000 hours of operation during a typical cooling season (i.e., 8 hours per day for 125 days per year).

text: Another method that yields the same result, is to calculate the total annual cooling output:

text: Then, for a SEER of 10, the annual electrical energy usage would be:

text: SEER is related to the coefficient of performance (COP) commonly used in thermodynamics and also to the Energy Efficiency Ratio (EER). The EER is the efficiency rating for the equipment at a particular pair of external and internal temperatures, while SEER is calculated over a whole range of external temperatures (i.e., the temperature distribution for the geographical location of the SEER test). SEER is unusual in that it is composed of an Imperial unit divided by an SI unit. The COP is a ratio with the same metric units of energy (joules) in both the numerator and denominator. They cancel out, leaving a dimensionless quantity. Formulas for the approximate conversion between SEER and EER or COP are available from the Pacific Gas and Electric Company:[32]

text: From equation (2) above, a SEER of 13 is equivalent to a COP of 3.43, which means that 3.43 units of heat energy are pumped per unit of work energy.

text: The United States now requires that residential systems manufactured in 2006 have a minimum SEER rating of 13 (although window-box systems are exempt from this law, so their SEER is still around 10).

text: Installation types[edit]

text: Window unit and packaged terminal[edit]

text: Window unit air conditioners are installed in an open window. The interior air is cooled as a fan blows it over the evaporator. On the exterior the heat drawn from the interior is dissipated into the environment as a second fan blows outside air over the condenser. A large house or building may have several such units, allowing each room to be cooled separately.

text: In 1971, General Electric introduced the first portable in-window air conditioner designed for convenience and portability.[33]

text: Packaged terminal air conditioner (PTAC) systems are also known as wall-split air conditioning systems.[34] They are ductless systems. PTACs, which are frequently used in hotels, have two separate units (terminal packages), the evaporative unit on the interior and the condensing unit on the exterior, with an opening passing through the wall and connecting them. This minimizes the interior system footprint and allows each room to be adjusted independently. PTAC systems may be adapted to provide heating in cold weather, either directly by using an electric strip, gas, or other heater, or by reversing the refrigerant flow to heat the interior and draw heat from the exterior air, converting the air conditioner into a heat pump. While room air conditioning provides maximum flexibility, when used to cool many rooms at a time it is generally more expensive than central air conditioning.

text: The first practical through-the-wall air conditioning unit was invented by engineers at Chrysler Motors and offered for sale starting in 1935.[35]

text: Split systems[edit]

text: Split-system air conditioners come in two forms: mini-split and central systems. In both types, the inside-environment (evaporative) heat exchanger is separated by some distance from the outside-environment (condensing unit) heat exchanger.

text: Mini-split (ductless) system[edit]

text: A mini-split system typically supplies air conditioned and heated air to a single or a few rooms of a building.[36] Multi-zone systems are a common application of ductless systems and allow up to 8 rooms (zones) to be conditioned from a single outdoor unit. Multi-zone systems typically offer a variety of indoor unit styles including wall-mounted, ceiling-mounted, ceiling recessed, and horizontal ducted. Mini-split systems typically produce 9,000 to 36,000 Btu (9,500–38,000 kJ) per hour of cooling. Multi-zone systems provide extended cooling and heating capacity up to 60,000 Btu's.

text: Advantages of the ductless system include smaller size and flexibility for zoning or heating and cooling individual rooms. The inside wall space required is significantly reduced. Also, the compressor and heat exchanger can be located farther away from the inside space, rather than merely on the other side of the same unit as in a PTAC or window air conditioner. Flexible exterior hoses lead from the outside unit to the interior one(s); these are often enclosed with metal to look like common drainpipes from the roof. In addition, ductless systems offer higher efficiency, reaching above 30 SEER.[37]

text: The primary disadvantage of ductless air conditioners is their cost. Such systems cost about US$1,500 to US$2,000 per ton (12,000 BTU per hour) of cooling capacity. This is about 30% more than central systems (not including ductwork) and may cost more than twice as much as window units of similar capacity."[38]

text: An additional possible disadvantage that the cost of installing mini splits can be higher than some systems, although lower operating costs and rebates or other financial incentives—offered in some areas—can help offset the initial expense.[39]

text: Central (ducted) air conditioning[edit]

text: Central (ducted) air conditioning offers whole-house or large-commercial-space cooling, and often offers moderate multi-zone temperature control capability by the addition of air-louver-control boxes.

text: In central air conditioning, the inside heat-exchanger is typically placed inside the central furnace/AC unit of the forced air heating system which is then used in the summer to distribute chilled air throughout a residence or commercial building.

text: Portable units[edit]

text: A portable air conditioner can be easily transported inside a home or office. They are currently available with capacities of about 5,000–60,000 BTU/h (1,500–18,000 W) and with or without electric-resistance heaters. Portable air conditioners are either evaporative or refrigerative.

text: The compressor-based refrigerant systems are air-cooled, meaning they use air to exchange heat, in the same way as a car radiator or typical household air conditioner does. Such a system dehumidifies the air as it cools it. It collects water condensed from the cooled air and produces hot air which must be vented outside the cooled area; doing so transfers heat from the air in the cooled area to the outside air.

text: Portable split system[edit]

text: A portable system has an indoor unit on wheels connected to an outdoor unit via flexible pipes, similar to a permanently fixed installed unit.

text: Portable hose system[edit]

text: Hose systems, which can be monoblock or air-to-air, are vented to the outside via air ducts. The monoblock type collects the water in a bucket or tray and stops when full. The air-to-air type re-evaporates the water and discharges it through the ducted hose and can run continuously.

text: A single-hose unit uses air from within the room to cool its condenser, and then vents it outside. This air is replaced by hot air from outside or other rooms (due to the negative pressure inside the room), thus reducing the unit's overall efficiency.[40]

text: Modern units might have a coefficient of performance of approximately 3 (i.e., 1 kW of electricity will produce 3 kW of cooling). A dual-hose unit draws air to cool its condenser from outside instead of from inside the room, and thus is more effective than most single-hose units. These units create no negative pressure in the room.

text: Portable evaporative system[edit]

text: Evaporative coolers, sometimes called "swamp coolers", do not have a compressor or condenser. Liquid water is evaporated on the cooling fins, releasing the vapor into the cooled area. Evaporating water absorbs a significant amount of heat, the latent heat of vaporisation, cooling the air. Humans and animals use the same mechanism to cool themselves by sweating.

text: Evaporative coolers have the advantage of needing no hoses to vent heat outside the cooled area, making them truly portable. They are also very cheap to install and use less energy than refrigerative air conditioners.

text: Uses[edit]

text: Air-conditioning engineers broadly divide air conditioning applications into comfort and process applications.

text: Comfort applications[edit]

text: Comfort applications aim to provide a building indoor environment that remains relatively constant despite changes in external weather conditions or in internal heat loads.

text: Air conditioning makes deep plan buildings feasible, for otherwise they would have to be built narrower or with light wells so that inner spaces received sufficient outdoor air via natural ventilation. Air conditioning also allows buildings to be taller, since wind speed increases significantly with altitude making natural ventilation impractical for very tall buildings.[citation needed] Comfort applications are quite different for various building types and may be categorized as:

text:
Commercial buildings, which are built for commerce, including offices, malls, shopping centers, restaurants, etc.
High-rise residential buildings, such as tall dormitories and apartment blocks
Industrial spaces where thermal comfort of workers is desired
Cars, aircraft, boats, which transport passenger or fresh goods
Institutional buildings, which includes government buildings, hospitals, schools, etc.
Low-rise residential buildings, including single-family houses, duplexes, and small apartment buildings
Sports stadiums, such as the University of Phoenix Stadium[41] and in Qatar for the 2022 FIFA World Cup.[42]

text: Women have, on average, a significantly lower resting metabolic rate than men.[43] Using inaccurate metabolic rate guidelines for air conditioning sizing can result in oversized and less efficient equipment,[43] and setting system operating setpoints too cold can result in reduced worker productivity.[44]

text: In addition to buildings, air conditioning can be used for many types of transportation, including automobiles, buses and other land vehicles, trains, ships, aircraft, and spacecraft.

text: Domestic usage[edit]

text: Air conditioning is common in the US, with 88% of new single-family homes constructed in 2011 including air conditioning, ranging from 99% in the South to 62% in the West.[45] In Canada, air conditioning use varies by province. In 2013, 55% of Canadian households reported having an air conditioner, with high use in Manitoba (80%), Ontario (78%), Saskatchewan (67%), and Quebec (54%) and lower use in Prince Edward Island (23%), British Columbia (21%), and Newfoundland and Labrador (9%).[46] In Europe, home air conditioning is generally less common. Southern European countries such as Greece have seen a wide proliferation of home air-conditioning units in recent years.[47] In another southern European country, Malta, it is estimated that around 55% of households have an air conditioner installed.[48] In India AC sales have dropped by 40% [clarification needed] due to higher costs and stricter energy efficiency regulations.[49]

text: Process applications[edit]

text: Process applications aim to provide a suitable environment for a process being carried out, regardless of internal heat and humidity loads and external weather conditions. It is the needs of the process that determine conditions, not human preference. Process applications include these:

text:
Chemical and biological laboratories
Cleanrooms for the production of integrated circuits, pharmaceuticals, and the like, in which very high levels of air cleanliness and control of temperature and humidity are required for the success of the process.
Environmental control of data centers
Facilities for breeding laboratory animals. Since many animals normally reproduce only in spring, holding them in rooms in which conditions mirror those of spring all year can cause them to reproduce year-round.
Food cooking and processing areas
Hospital operating theatres, in which air is filtered to high levels to reduce infection risk and the humidity controlled to limit patient dehydration. Although temperatures are often in the comfort range, some specialist procedures, such as open heart surgery, require low temperatures (about 18 °C, 64 °F) and others, such as neonatal, relatively high temperatures (about 28 °C, 82 °F).
Industrial environments
Mining
Nuclear power facilities
Physical testing facilities
Plants and farm growing areas
Textile manufacturing

text: In both comfort and process applications, the objective may be to not only control temperature, but also humidity, air quality, and air movement from space to space.

text: Health effects[edit]

text: Air-conditioning systems can promote the growth and spread of microorganisms,[50] such as Legionella pneumophila, the infectious agent responsible for Legionnaires' disease, or thermophilic actinomycetes; however, this is only prevalent in poorly maintained water cooling towers. As long as the cooling tower is kept clean (usually by means of a chlorine treatment), these health hazards can be avoided or reduced.

text: Conversely, air conditioning (including filtration, humidification, cooling and disinfection) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where proper atmosphere is critical to patient safety and well-being. Excessive air conditioning can have a negative effect on skin, causing it to dry out, and can also cause dehydration.[citation needed]

text: Environmental impacts[edit]

text: Power consumption[edit]

text: Innovation in air conditioning technologies continues, with much recent emphasis placed on energy efficiency. Production of the electricity used to operate air conditioners has an environmental impact, including the release of greenhouse gases.

text: Cylinder unloaders are a method of load control used mainly in commercial air conditioning systems. [51] On a semi-hermetic (or open) compressor, the heads can be fitted with unloaders which remove a portion of the load from the compressor so that it can run better when full cooling is not needed. Unloaders can be electrical or mechanical.

text: Use of programmable thermostats[edit]

text: In the United States, 87 percent of the homes use air conditioning and 65 percent of those homes having central air conditioning. Most of the homes with central air conditioning have programmable thermostats, but approximately two-thirds of the homes with central air do not use the features of them to make their homes more energy efficient.[52]

text: Automobile power consumption[edit]

text: In an automobile, the A/C system will use around 4 horsepower (3 kW) of the engine's power, thus increasing fuel consumption of the vehicle.[53]

text: Refrigerants[edit]

text: Most refrigerants used for air conditioning contribute to global warming, and many also deplete the ozone layer.[54] CFCs, HCFCs, and HFCs are potent greenhouse gases when leaked to the atmosphere.

text: The use of CFC as a refrigerant was once common, including the refrigerants R-11 and R-12 (sold under the brand name Freon-12). Freon refrigerants were commonly used during the 20th century in air conditioners due to their superior stability and safety properties. When they are released accidentally or deliberately, these chlorine-bearing refrigerants eventually reach the upper atmosphere.[55] Once the refrigerant reaches the stratosphere, UV radiation from the Sun homolytically cleaves the chlorine-carbon bond, yielding a chlorine radical. These chlorine radicals catalyze the breakdown of ozone into diatomic oxygen, depleting the ozone layer that shields the Earth's surface from strong UV radiation. Each chlorine radical remains active as a catalyst until it binds with another radical, forming a stable molecule and quenching the chain reaction.

text: Prior to 1994, most automotive air conditioning systems used R-12 as a refrigerant. It was replaced with R-134a refrigerant, which has no ozone depletion potential. Old R-12 systems can be retrofitted to R-134a by a complete flush and filter/dryer replacement to remove the mineral oil, which is not compatible with R-134a.

text: R22 (also known as HCFC-22) has a global warming potential about 1,800 times higher than CO2.[56] It was phased out for use in new equipment by 2010, and is to be completely discontinued by 2020. Although these gasses can be recycled when air conditioning units are disposed of, uncontrolled dumping and leaking can release gas directly into the atmosphere.

text: In the UK, the Ozone Regulations[57] came into force in 2000 and banned the use of ozone depleting HCFC refrigerants such as R22 in new systems. The Regulation banned the use of R22 as a "top-up" fluid for maintenance between 2010 (for virgin fluid) and 2015 (for recycled fluid). This means that equipment that uses R22 can still operate, as long as it does not leak. Although R22 is now banned, units that use the refrigerant can still be serviced and maintained.[58]

text: The manufacture and use of CFCs has been banned or severely restricted due to concerns about ozone depletion (see also Montreal Protocol).[59][60] In light of these environmental concerns, beginning on November 14, 1994, the U.S. Environmental Protection Agency has restricted the sale, possession and use of refrigerant to only licensed technicians, per rules under sections 608 and 609 of the Clean Air Act.[61]

text: As an alternative to conventional refrigerants, other gases, such as CO2 (R-744), have been proposed.[62] R-744 is being adopted as a refrigerant in Europe and Japan. It is an effective refrigerant with a global warming potential of 1, but it must use higher compression to produce an equivalent cooling effect.[citation needed]

text: In 1992, a non-governmental organization, Greenpeace, was spurred by corporate executive policies and requested that a European lab find substitute refrigerants. This led to two alternatives, one a blend of propane (R290) and isobutane (R600a), and one of pure isobutane.[17][20] Industry resisted change in Europe until 1993, and in the U.S. until 2011, despite some supportive steps in 2004 and 2008 (see Refrigerant Development above).[25][63]


document_title: Ages of consent in Africa

question_text: what's the age of consent in nigeria

question_tokens: what 's the age of consent in nigeria

root

text: Ages of consent in Africa

text: Consent by age[edit]

text:
Age

Countries (links are to sections on this page)

8

Angola

13

Burkina Faso, Comoros, Niger, Sahrawi Arab Democratic Republic

14

Botswana (Males), Cape Verde, Chad, Democratic Republic of the Congo (Females), Lesotho, Madagascar, Madeira (Portugal), São Tomé and Príncipe

15

French Southern and Antarctic Lands (France), Îles Éparses (France), Guinea, Mayotte (France), Morocco, Réunion (France)

16

Algeria, Botswana (Females), Cameroon, Ceuta (Spain), Canary Islands, Ghana, Guinea-Bissau, Mauritania, Melilla (Spain), Malawi, Mauritius, Mozambique, Namibia (Girls), Plazas de soberanía (Spain), Senegal, South Africa, Saint Helena, Ascension and Tristan da Cunha (United Kingdom), Swaziland, Togo, Zambia, Zimbabwe

18

Benin, Burundi, Central African Republic, Côte d'Ivoire, Democratic Republic of the Congo (Males), Djibouti, Egypt, Equatorial Guinea, Eritrea, Ethiopia, Gabon, Gambia, Kenya, Liberia, Mali, Nigeria, Republic of the Congo, Rwanda, Seychelles, Sierra Leone, South Sudan, Somalia, Tanzania, Tunisia, Uganda

Must be Married

Libya, Sudan

tag: table

text: Algeria[edit]

text: The age of consent in Algeria is 16 for vaginal intercourse. "Heterosexual Sodomy" (anal and/or oral sex with an opposite-sex partner) is illegal, Article 388 of the Penal Code. As well as all same-sex sexual conduct, Article 338, and "outrages to public decency", Article 333. The punishment for both the first two activities with those under 18 years of age is more severe for the older participant.[1]

tag: p

text: Angola[edit]

text: The age of consent in Angola is 5 regardless of sexual orientation and/or gender.[2] However, while rarely prosecuted, sexual relations with a child between the ages of 5 and 10 are considered sexual abuse which is punishable with up to 8 years in prison.[3]

text: Benin[edit]

text: The age of consent in Benin is 18 regardless of sexual orientation and/or gender.[4]

text: Botswana[edit]

text: The age of consent is 16, but homosexuality is punishable by 7 years' imprisonment.[5]

text: Burkina Faso[edit]

text: The age of consent is equally set at 13 regardless of sexual orientation and/or gender.[6]

text: Burundi[edit]

text: Under the new Penal Code of 2009 (in French), the age of consent in Burundi for heterosexuals (both men and women) is 18 years.[6]  However, under Article 567, homosexual acts (both men and women) carry a fine of up to 100,000 Burundian francs and up to 3 years imprisonment.[7]

text: Cameroon[edit]

text: The age of consent in Cameroon is 16.[8]

text: Cape Verde[edit]

text: The age of consent in Cape Verde is 14 regardless of sexual orientation and/or gender.[9]

text: Central African Republic[edit]

text: The minimum age of sexual consent is 18 years of age regardless of sexual orientation and/or gender.[9]

text: Ceuta (Spain)[edit]

text: The age of consent in Ceuta for both males and females is 16, as it is under Spanish sovereignty, as of 1 July 2015.[10]

text: Chad[edit]

text: The age of consent in Chad is 14 for girls, even if she is married, but the ban is rarely enforced.[11] The age of consent for boys is not known.[clarification needed]

text: Comoros[edit]

text: The age of consent in the Comoros is 13.[12]

text: Côte d'Ivoire[edit]

text: The age of consent in Côte d'Ivoire is 18 regardless of sexual orientation and/or gender.[13]

text: Canary Islands (Spain)[edit]

text: The age of consent in Ceuta for both males and females is 16, as it is under Spanish sovereignty, as of 1 July 2015.[14]

text: Democratic Republic of the Congo[edit]

text: The age of consent in the Democratic Republic of the Congo is 14 for females and 18 for males.[15]

text: Djibouti[edit]

text: The age of consent is 18 regardless of sexual orientation and/or gender.[16]  Although Djiboutian law establishes that parties to a marriage should be 18 or over, there is an exemption in cases where minors may marry with the consent of their guardians.  Effectively this means the age of consent is lower than 18, especially in rural areas; in 2007, 13.6% of married women under the age of 50 married before the age of 18.[17]

text: Egypt[edit]

text: The age of consent in Egypt is 18 years, for heterosexual males and females. Sex work is illegal and the sex work law has been used against male and female homosexuals.[18]

text: Equatorial Guinea[edit]

text: The age of consent is 18 regardless of sexual orientation and/or gender.[19]

text: Eritrea[edit]

text: The age of consent in Eritrea is 18, as stipulated by Article 595.[20]

text: Ethiopia[edit]

text: The minimum age for consensual sex is 18 years.[9]  The law, however, is not enforced; nearly 20% of girls are married by the age of 15.  Early childhood marriage is especially common in rural areas, where some girls are married as young as 7 years old.[21]

text: French Southern and Antarctic Lands (France)[edit]

text: The age of consent in the French Southern and Antarctic Lands for both males and females is 15, as it is under French sovereignty

text: Îles Éparses (France)[edit]

text: The age of consent in Îles Eparses for both males and females is 15, as it is under French sovereignty

text: Gabon[edit]

text: The age of consent in Gabon is 18 regardless of sexual orientation and/or gender.[22]

text: Gambia[edit]

text: The age of consent is 18.[23]

text: Ghana[edit]

text: The age of consent is 18.[24]

text: Guinea[edit]

text: The age of consent is 15.[25]

text: Guinea-Bissau[edit]

text: The age of consent is 16 regardless of sexual orientation and/or gender.[26]

text: Kenya[edit]

text: The age of consent in Kenya is 18 years, as children are defined under 18 and are not able to give consent.[27]  Marriage is not possible below the age of 18, the law is clear about this.[28]  Male homosexuality in Kenya is illegal; female homosexuality is illegal.[29]

text: Lesotho[edit]

text: The age of consent is 14 years, regardless of sexual orientation and/or gender [30]

text: Liberia[edit]

text: The age of consent in Liberia is 18.[31] Statutory rape is a first-degree rape offense which carries a maximum sentence of life imprisonment. The age of consent was raised to 18, from 16, in 2009.[32][33]

text: Libya[edit]

text: During the Gaddafi government, the regular age of consent was 18, but 16 years old women could be married as long the parents consented. Pre-marital sex was illegal.

text: After the 2011 revolution, the age of consent limit was removed. Presently, there is no defined age of consent, although sex is not allowed outside of marriage.[34] However, the law is practically never enforced due to the Libyan Civil War.

text: Madagascar[edit]

text: Age of consent is 14 years, according to article 331 in the Criminal Law. In certain cases, including relatives and homosexuals, it is 21 years.[35]

text: Malawi[edit]

text: The age of consent is 16 regardless of sexual orientation and/or gender.[36]

text: Mali[edit]

text: The age of consent is 18 regardless of sexual orientation and/or gender.[37]

text: Mauritania[edit]

text: The age of consent is 16.[38] However, under section 306 of the Legal Code, any act that violates Islamic Morality is illegal, but a clear definition of morality does not exist in the country's laws, so it is very open to interpretation by local officials as to what is moral and what is not. Thus, many acts surrounding the age of consent could be considered illegal.[39]

text: Mauritius[edit]

text: The age of consent in Mauritius is 16 regardless of sexual orientation and/or gender.

text: Article 249 ‘Rape, attempt upon chastity and illegal sexual intercourse’ of the Penal Code:[40]

text:
(...) Any person who has sexual intercourse with a female 'under the age of sixteen (16),
even with consent, shall be liable to penal servitude not exceeding ten (10) years.

text: Madeira (Portugal)[edit]

text: The age of consent in Madeira for both males and females is 14, as it is under Portuguese sovereignty

text: Mayotte (France)[edit]

text: The age of consent in Mayotte for both males and females is 15, as it is under French sovereignty

text: Melilla (Spain)[edit]

text: The age of consent in Melilla for both males and females is 16, as it is under Spanish sovereignty, as of 1 July 2015.[41]

text: Morocco[edit]

text: The age of consent is 18, per Art. 484 of the Penal Code.[42][43][44]

text: Mozambique[edit]

text: The age of consent is 16 regardless of sexual orientation and/or gender.[45]

text: Namibia[edit]

text: The age of consent is 16 for girls.

text:
‘Sexual offences with girls under sixteen (16) years’, Section 14 of the
'Combating of Immoral Practices Act 1980'

text: '(1) Any male who

text: a) has or attempts to have unlawful carnal intercourse with a girl under the age of sixteen (16) years; or

text: b) commits or attempts to commit with such a girl an immoral or indecent act;

text:
c) solicits or entices such a girl to the commission of an immoral or indecent act,
-shall be guilty of an offence and liable on conviction to imprisonment for a period
not exceeding six years with or without a fine not exceeding three thousand rand in
addition to such imprisonment.

text:
(2) It shall be a sufficient defence to any charge in terms of this section if it appears
to the court -

text:
a) that the girl at the time of the commission of the offence was a prostitute, that
the person so charged was at the said time under the age of twenty-one (21) years
and that it is the first occasion on which he is so charged; or

text:
b) that the person who charged was at the said time under the age of sixteen (16)
years ; and

text:
c) that the girl or person in whose charge she was, deceived the person so charged
into believing that she was over the age of sixteen (16) years at the said time.' [46]

text: Niger[edit]

text: In Niger, the age of consent is 13 years.[47]

text: Nigeria[edit]

text:
The age of consent is 18 years.[48]
[Section 31 of the Child's Rights Act 2003.  Also Sections 21 and 22 of the same Act prohibit Child marriage or betrothal.]
However, homosexuality is illegal.

text: Plazas de soberanía (Spain)[edit]

text: The age of consent in Plazas de soberania for both males and females is 16, as it is under Spanish sovereignty, as of 1 July 2015.[49]

text: Republic of the Congo[edit]

text: The age of consent in the Republic of the Congo is 18 regardless of sexual orientation and/or gender. Sex with a minor is punishable by up to 5 years in prison and a fine of 10,000,000 CFA.[50]

text: Réunion (France)[edit]

text: Rwanda[edit]

text: The age of consent in Rwanda is 18 years, regardless of sexual orientation and/or gender.[18]

text: São Tomé and Príncipe[edit]

text: The age of consent in São Tomé and Príncipe is 14 years, regardless of sexual orientation and/or gender.[51]

text: Senegal[edit]

text: The age of consent in Senegal is 16 (Article 320 deals with children under 16; Article 319 deals with children under 13). Homosexual sex is illegal.[52]

text: Seychelles[edit]

text: The age of consent is 18 regardless of sexual orientation and/or gender.[53]

text: According to the U.S. State Department, the Seychelles age of consent is "traditionally understood" to be 15 but that the country's statutes "fail to clearly define the ages of consent and legal majority"; according to the State Department this causes confusion in regards to the "traditionally understood" age of consent and the age of majority of 18 and therefore complicates enforcement of the law.[54]

text: Sierra Leone[edit]

text: The age of consent is 18 regardless of sexual orientation and/or gender, under the new Sexual Offenses Act 2012.[55]

text: Somalia[edit]

text: Article 29 of the national constitution of Somalia defines a child as any individual under the age of 18, and stipulates that "every child has the right to be protected from mistreatment, neglect, abuse, or degradation." This information, however, does not prove that there is an actual age of consent, thus making it difficult to draw a line.[56] Homosexual sex is illegal.[57]

text: South Africa[edit]

text: The age of consent in South Africa is 16, as specified by sections 15 and 16 of the Criminal Law (Sexual Offences and Related Matters) Amendment Act, 2007. Section 15 ("statutory rape") prohibits the commission of "an act of sexual penetration with a child who is 12 years of age or older but under the age of 16 years", while section 16 ("statutory sexual assault") prohibits the commission of "an act of sexual violation with a child who is 12 years of age or older but under the age of 16 years".[58] The law includes a close-in-age exception, so that sexual acts between two children where both are between 12 and 16, or where one is under 16 and the other is less than two years older, are not criminal.[58] Children under the age of 12 are conclusively presumed by the law to be incapable of consenting, so a sexual act with a child under that age constitutes rape or sexual assault.[59]

text: History[edit]

text: Under the Roman-Dutch common law there was a conclusive presumption that girls under the age of 12 were unable to consent to sexual intercourse.[60] This presumption can be traced back to the "old authorities" of the seventeenth century.[61]

text: The Girls' and Mentally Defective Women's Protection Act, 1916, which replaced the differing age of consent laws of the four colonies that formed the Union of South Africa, criminalised sexual intercourse between a man and a girl under the age of sixteen unless they were married. This act was replaced by a similar prohibition in section 14 of the Immorality Act, 1957.  Although sex between men was already illegal, prohibited by the common law as "sodomy" or "unnatural sexual acts", the Immorality Act also criminalised sexual intercourse between a man and a boy under sixteen.

text: The Immorality Amendment Act, 1969, which was enacted in response to a national moral panic over homosexuality, raised to 19 the age below which the Immorality Act prohibited sex between males. The Immorality Amendment Act, 1988 inserted mirror provisions applying to women, prohibiting intercourse between a woman and a boy under 16 or a girl under 19. It also renamed the Immorality Act to the Sexual Offences Act, 1957.

text: The Interim Constitution, which came into force in 1994, prohibited discrimination on the basis of sexual orientation, as does the final Constitution which replaced in 1997. As a result, the Constitutional Court struck down the laws prohibiting homosexual sex in the 1998 case of National Coalition for Gay and Lesbian Equality v Minister of Justice. That case did not, however, address the difference between the heterosexual and homosexual ages of consent in section 14 of the Sexual Offences Act.

text: In the Criminal Law (Sexual Offences and Related Matters) Amendment Act, 2007, Parliament reformed and codified the law on sexual offences and made it gender-neutral. The common-law presumption relating to girls under 12 was replaced by a general presumption that children under 12 cannot consent. The act also fixed the age of consent at 16 for all sexual acts. In the 2008 case of Geldenhuys v National Director of Public Prosecutions, the Constitutional Court held that the former difference in the ages of consent had been unconstitutional.[62]

text: South Sudan[edit]

text: The age of consent in South Sudan is 18.[63][64][65][66]

text: Saint Helena, Ascension and Tristan da Cunha (United Kingdom)[edit]

text: Age of sexual consent is 16, regardless of sexual orientation and/or gender

text: Sudan[edit]

text: Intercourse in Sudan is against the law if not married.[67]

text: Swaziland[edit]

text: The age of consent is 16.

text:
A girl under the age of fourteen (14) cannot consent to sexual intercourse under criminal law. However, under Statutory Law, according to the Girls and Women
Protection Act, a girl under the age of sixteen (16) can not in any way consent to sexual intercourse.[68]

text: Tanzania[edit]

text: The age of consent is 18 in Tanzania, but as of 2010/2011 the law is not enforced.[69]

text: Togo[edit]

text: The age of consent in Togo is 16.[70]

text: Tunisia[edit]

text: The age of consent in Tunisia is 18 (since 2010). However, there appears to be a marital exception in the law that allows a minor over 15 to consent to sex with an adult if the minor is married to the adult.[71][72]

text: Uganda[edit]

text: The age of consent in Uganda is 18 years, for vaginal intercourse.[73][74] "Heterosexual sodomy" (anal and/or oral sex with an opposite-sex partner) and all same-sex sexual conduct was illegal until January 2014 when President Museveni blocked the anti-gay law.

text: Zambia[edit]

text: The age of consent is 16.[75]

text: Zimbabwe[edit]

text: The age of consent is 16.[76]

text: All male same-sex hand-holding and/or male same-sex sexual conduct can lead to one year's imprisonment.[citation needed] Same-sex hand-holding is illegal.[77]


document_title: Mike Evans (actor)

question_text: who played the original lionel on the jeffersons

text: Mike Evans (actor)

text: Early life[edit]

text: Evans was born in Salisbury, North Carolina. His father, Theodore Evans Sr., was a dentist, and his mother, Annie Sue Evans, a teacher. He attended Palmer Memorial Institute, a private school for young black Americans in Sedalia, North Carolina just outside Greensboro. His family later moved to Los Angeles, where he graduated from Los Angeles High School. He studied acting at Los Angeles City College.[1]

text: Career[edit]

text: Evans is best known for his recurring role as Lionel Jefferson on All in the Family and was the first and final actor to play Lionel on the spin-off The Jeffersons. He played Lionel on The Jeffersons for much of its 11-year run, with the majority of his appearances occurring from 1979 to 1981. Actor and opera singer Damon Evans (no relation to Michael) played the role from September 1975 to January 1978 on The Jeffersons, as Mike Evans was busy pursuing other aspects of his career.

text: Evans was also one of the creators and writers of the series Good Times (1974-79).[2]

text: Evans played Lenny in the cast of the 1976-1977 Danny Thomas situation comedy The Practice during its second and final season.

text: Evans was also a real estate investor and owned properties in California's Inland Empire.[3]

text: Actress Berlinda Tolbert who played Evans' wife, Jenny, on The Jeffersons is just one day younger and they were also both born in North Carolina.

text: Personal life and death[edit]

text: In July 1974, Evans met Helena Jefferson (June 18, 1952 – September 11, 2002). They married on January 10, 1976. On September 11, 2002, Evans lost his wife to breast cancer after she was diagnosed on February 24, 2001. Four years after her death, Evans died of throat cancer at his mother's home in Twentynine Palms, California at the age of 57.[3]

text: Filmography[edit]

text:
Year
Title
Role
Notes

1971–75
All in the Family
Lionel Jefferson
Main cast (33 episodes)

1972
Killer by Night
Marley
Television film

1972
Call Her Mom
Wilson
Television film

1972
Now You See Him, Now You Don't
Henry Fathington
Feature film

1972
Love, American Style
Jerome Wilson
"Love and the Perfect Wedding" segment

1973
Voyage of the Yes
Orlando B. Parker
Television film

1974
The House on Skull Mountain
Phillippe Wilette
Television film

1974
The Streets of San Francisco
Paul Hudson
Episode: "For Good or Evil"

1975
Far Out Space Nuts

Episode: "Galaxy's Greatest Athlete"

1975; 1979–81;
1985
The Jeffersons
Lionel Jefferson
Main cast (34 episodes)

1976
Rich Man, Poor Man
Arnold Simms
Television miniseries

1976–77
The Practice
Lenny
Main cast (13 episodes)


document_title: Search box

question_text: what do we type into a search bar

question_tokens: what do we type into a search bar

text: Search box

text: This article does not cite any sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (February 2011) (Learn how and when to remove this template message)

text: A search box, search field or search bar is a graphical control element used in computer programs, such as file managers or web browsers, and on web sites. A search box is usually a single-line text box or search icon ( which will transform into a search box on click activity) with the dedicated function of accepting user input to be searched for in a database. Search boxes on web pages are usually used to allow users to enter a query to be submitted to a Web search engine server-side script, where an index database is queried for entries that contain one or more of the user's keyword research.

text: Search boxes are commonly accompanied by a search button (sometime indicated only by a magnifying glass symbol) to submit the search. However, the search button may be omitted as the user may press the enter key to submit the search, or the search may be sent automatically to present the user with real-time results.

text: Common features[edit]

text: Depending on the particular implementation, a search box may be accompanied by a drop-down list to present the users with past searches or search suggestions. Search boxes may have other features to help the user, such as autocomplete, search suggestions, a spelling checker, etc. Search boxes are often also accompanied by drop-down menus or other input controls to allow the user to restrict the search or choose what type of content to search for.

text: In some cases, while users input search strings, the results of that string would also present on the content area too. However, if the page choose this way to show results to users, the loading time is pretty slow and sometimes it may cause freezing state or browser crash. Hence, it is not recommend for small and medium size webpage.


document_title: Tanks in World War I

question_text: when was the first tank used in battle

question_tokens: when was the first tank used in battle

text: Tanks in World War I

text: Conceptual roots of the tank[edit]

text: The conceptual roots of the tank go back to ancient times, with siege engines which were able to provide protection for troops moving up against stone walls or other fortifications. With the coming of the Industrial Revolution and the demonstrable power of steam, James Cowan presented a proposal for a Steam Powered Land Ram in 1855, towards the end of the Crimean War. Looking like a helmet on 'footed' Boydell wheels, early forerunners of the Pedrail wheel, it was essentially an armoured steam tractor equipped with cannon and rotating scythes sprouting from the sides. Lord Palmerston is said to have dismissed it as 'barbaric'.

text: From 1904 to 1909, David Roberts, the engineer and managing director of Hornsby & Sons of Grantham, built a series of tractors using his patented 'chain-track' which were put through their paces by the British Army, a (small) section of which wanted to evaluate artillery tractors. At one point in 1908, Major William E. Donohue of the Mechanical Transport Committee remarked to Roberts that he should design a new machine with armour, capable of carrying its own gun. But, disheartened by years of ultimately fruitless tinkering for the Army, Roberts did not take up the idea. In later years he expressed regret at not having pursued it.[5]

text: An engineer in the Austro-Hungarian Army, Lieutenant Gunther Burstyn, inspired by Holt tractors, designed a tracked armoured vehicle in 1911 carrying a light gun in a rotating turret; equipped also with hinged 'arms', two in front and two at the rear, carrying wheels on the ends to assist with obstacles and trenches, it was a very forward-looking design, if rather small. The Austrian government said it would be interested in evaluating it if Burstyn could secure commercial backing to produce a prototype. Lacking the requisite contacts, he let it drop. An approach to the German government was similarly fruitless.

text: In 1912, A South Australian, Lancelot De Mole, submitted a proposal to the British War Office for a "chain-rail vehicle which could be easily steered and carry heavy loads over rough ground and trenches". De Mole made several more proposals to the War Office after 1912, in 1914 and 1916, with a culminating proposal in late 1917, accompanied by a huge one-eighth scale model, yet all fell on substantially deaf ears. De Mole's proposal already had the climbing face, so typical of the later World War I British tanks, but it is unknown whether there was some connection. Inquiries from the government of Australia, after the war, yielded polite responses that Mr. De Mole's ideas had unfortunately been too advanced for the time to be properly recognised at their just value. The Commission on Awards to Inventors in 1919, which adjudicated all the competing claims to the development of the tank, recognised the brilliance of De Mole's design, even considering that it was superior to the machines actually developed, but due to its narrow remit, could only make a payment of £987 to De Mole to cover his expenses. De Mole noted in 1919 that he was urged by friends before the war to approach the Germans with his design, but declined to do so for patriotic reasons.

text: Before World War I, motorized vehicles were still relatively uncommon, and their use on the battlefield was initially limited, especially of heavier vehicles. Armoured cars soon became more commonplace with most belligerents, especially in more open terrain. On August 23, 1914, the French Colonel Jean Baptiste Eugène Estienne, later a major proponent of tanks, declared: Messieurs, la victoire appartiendra dans cette guerre à celui des deux belligérants qui parviendra le premier à placer un canon de 75 sur une voiture capable de se mouvoir en tout terrain ("Gentlemen, the victory will belong, in this war, to the one of the two belligerents who will be the first to succeed in mounting a 75 mm gun on a vehicle capable of moving in all types of terrain").

text: Armored cars did indeed prove useful in open land such as in deserts, but were not very good at crossing obstacles (e.g. trenches, barriers) or in more challenging terrain. The other issue was that it was very hard to add much protection or armament.

text: The main limitation was the wheels, which gave a high ground pressure for the vehicle's weight. This could be solved by adding more wheels, but unless they also were driven, the effect was to reduce traction on the powered wheels. Driving extra wheels meant more drive train weight, in turn requiring a larger and heavier engine to maintain performance. Even worse, none of this extra weight was put into an improvement of armor or armament carried, and the vehicles were still incapable of crossing very rough terrain.

text: The adoption of caterpillar tracks offered a new solution to the problem. The tracks spread the weight of the vehicles over a much greater area, which was all used for traction to move the vehicle. The limitation on armor and firepower was no longer ground pressure but the power and weight of the power-plant.

text: The remaining issue was how to utilise and configure a vehicle. Major Ernest Dunlop Swinton RE, was the official British war correspondent serving in France in 1914. He recounts in his book Eyewitness how the idea of using caterpillar tracks to drive an armoured fighting vehicle came to him on October 19, 1914, while he was driving through northern France. In July 1914 he had received a letter from a friend, Hugh Marriott, a mining engineer, drawing his attention to a Holt caterpillar tractor that Marriott had seen in Belgium. Marriott thought it might be useful for transport over difficult ground, and Swinton had passed the information on to the appropriate departments. Now Swinton suggested the idea of an armoured tracked vehicle to the military authorities, by sending a proposal to Lieutenant-Colonel Maurice Hankey. Hankey in turn tried to interest Lord Kitchener in the idea; when this failed he sent a memorandum in December to the Committee of Imperial Defence, of which he was himself the secretary; Winston Churchill the First Lord of the Admiralty was one of the members of the committee. Hankey proposed to build a gigantic steel roller, pushed by tracked tractors, to shield the advancing infantry. Churchill in turn wrote a note on January 5 to the Prime Minister H. H. Asquith, in which he warned that the Germans might any moment introduce a comparable system. A worried Asquith now ordered Kitchener to form a committee, headed by General Scott-Moncrieff, to study the feasibility of Swinton's idea; however, after trials with a Holt 75 h.p. machine the committee concluded in February 1915 that the idea was impractical.

text: The Landships Committee[edit]

text: Winston Churchill however decided that if the Army wouldn't take up the idea, the Navy should proceed independently, even if it were to exceed the limits of his authority. He created the Landships Committee in February 1915, initially to investigate designs for a massive troop transporter. As a truer picture of front-line conditions was developed the aims of the investigation changed. A requirement was formulated for an armoured vehicle capable of 4 mph (6 km/h), climbing a 5 feet (1.5 m) high parapet, crossing an 8 feet (2.4 m) wide gap, and armed with machine guns and a light artillery piece. A similar proposal was working its way through the Army GHQ in France, and in June the Landships Committee was made a joint service venture between the War Office and the Admiralty. The Naval involvement in Armoured Fighting Vehicle (AFV) design had originally come about through the Royal Naval Air Service Armoured Car Division, the only British unit fielding AFVs in 1914; surprisingly, until the end of the war most experimentation on heavy land vehicles was conducted by Royal Naval Air Service Squadron 20.

text: At first, protecting heavy gun tractors with armour appeared the most promising line of development. Alternative early 'big wheel' designs on the lines of the Russian tsar tank of 1915 were soon understood to be impractical. However, adapting the existing Holt Company caterpillar designs — the only robust tracked tractors available in 1915 — into a fighting machine, as France and Germany did, was decided against. While armour and weapon systems were easy to acquire, other existing caterpillar and suspension units were too weak, existing engines were underpowered for the vehicles that the designers had in mind, and trench-crossing ability was poor because of the shortness of the wheelbase. The Killen-Strait tractor with three tracks was used for the first experiments in June but was much too small to be developed further. The large Pedrail monotrack vehicle proved to be unsuitable. Trials to couple two American Bullock tractors failed. There also were considerable differences of opinion between the several committee members. Col R.E.B. Crompton, a veteran military engineer and electrical pioneer, drafted numerous designs with Lucien Legros for armoured troop carrying vehicles and gun-armed vehicles, to have used either Bullock tracks or variants of the Pedrail. At the same time, Lt Robert Macfie, of the RNAS, and Albert Nesfield, an Ealing-based engineer, devised a number of armoured tracked vehicles, which incorporated an angled front 'climbing face' to the tracks. The two men fell out bitterly as their plans came to nought; Macfie in particular pursued a vendetta against the other members of the Landships Committee after the war.

text: To resolve the threatened dissipation of effort, it was ordered in late July that a contract was to be placed with William Foster & Co. Ltd, a company having done some prewar design work on heavy tractors and known to Churchill from an earlier experiment with a trench-crossing supply vehicle, to produce a proof-of-concept vehicle with two tracks, based on a lengthened Bullock tractor chassis. Construction work began three weeks later.

text: Fosters of Lincoln built the 14 ton "Little Willie", which first ran on 8 September. Powered by a 105 hp (78 kW) Daimler engine, the 10-foot-high (3.0 m) armoured box was initially fitted with a low Bullock caterpillar. A rotating top turret was planned with a 40 mm gun but abandoned due to weight problems, leaving the final vehicle unarmed and little more than a test-bed for the difficult track system. Difficulties with the commercial tracks supplied led to Tritton designing a completely new track system different from, and vastly more robust than, any other system then in use. The next design by Lieutenant Walter Gordon Wilson RNAS, a pre-war motor engineer, added a larger track frame to the hull of "Little Willie". In order to achieve the demanded gap clearance a rhomboidal shape was chosen—stretching the form to improve the track footprint and climbing capacity. To keep a low centre of gravity the rotating turret design was dropped in favour of sponsons on the sides of the hull fitted with naval 6-pounder (57 mm) guns. A final specification was agreed on in late September for trials in early 1916, and the resulting 30 ton "Big Willie" (later called "Mother") together with "Little Willie" underwent trials at Hatfield Park on 29 January and 2 February. Attendees at the second trial included Lord Kitchener, Lloyd George, Reginald McKenna and other political luminaries. On 12 February an initial order for 100 "Mother" type vehicles was made, later expanded to 150.

text: Although landship was a natural term coming from an Admiralty committee, it was considered too descriptive and could give away British intentions. The committee therefore looked for an appropriate code term for the vehicles. Factory workers assembling the vehicles had been told they were producing "mobile water tanks" for desert warfare in Mesopotamia. Water Container was therefore considered but rejected because the committee would inevitably be known as the WC Committee (WC meaning water closet was a common British term for a toilet). The term tank, as in water tank, was in December 1915 finally accepted as its official designation. From then on, the term "tank" was established among British and also German soldiers. While in German Tank specifically refers to the World War I type (as opposed to modern Panzer), in English, Russian and other languages the name even for contemporary armoured vehicles is still based on the word tank.

text: It is sometimes mistakenly stated that, after completion, the tanks were shipped to France in large wooden crates. For secrecy and in order to not arouse any curiosity, the crates and the tanks themselves were then each labelled with a destination in Russian, "With Care to Petrograd". In fact the tanks were never shipped in crates: the inscription in Russian was applied on the hull for their transport from the factory to the first training centre at Thetford.

text: The first fifty had been delivered to France on 30 August. They were 'male' or 'female', depending upon whether their armament comprised two 6-pounder cannon and three Hotchkiss machine guns or four Vickers machine guns and one Hotchkiss. It had a crew of eight, four of whom were needed to handle the steering and drive gears. The tanks were capable of, at best, 6 km/h (4 mph), matching the speed of marching infantry with whom they were to be integrated to aid in the destruction of enemy machine guns. In practice, their speed on broken ground could be as little as 1 mph.

text: After the war the Royal Commission on Awards to Inventors decided that the principal inventors of the Tank were Sir William Tritton, managing director of Fosters, and Major Walter Gordon Wilson.

text: First deployments[edit]

text: The first use of tanks on the battlefield was the use of British Mark I tanks at the Battle of Flers-Courcelette (part of the Battle of the Somme) on 15 September 1916, with mixed results; many broke down, but nearly a third succeeded in breaking through. Of the forty-nine tanks shipped to the Somme, only thirty-two were able to begin the first attack in which they were used and only nine made it across "no man's land" to the German lines. The tanks had been rushed into combat before the design was mature enough (against Churchill's and Ernest Swinton's wishes)[6] and the number was small but their use gave important feedback on how to design newer tanks, the soundness of the concept, and their potential to affect the course of the war. On the other hand, the French Army was critical of the British employment of small numbers of tanks at this battle. They felt the British had sacrificed the secrecy of the weapon while employing it in numbers too small to be decisive. Considering that the British attack was part of an Anglo-French offensive while the Russians were also attacking at the same time, Haig felt justified in making a maximum effort, regardless of the limitations of the tank force.

text: The Mark Is were capable of performing on the real battlefield of World War I, one of the most difficult battlefield terrains ever. They did have reliability problems, but when they were working they could cross trenches or craters of 9 feet (2.7 m) and drive right through barbed wire. It was still common for them to get stuck, especially in larger bomb craters, but overall the rhomboid shape allowed for extreme terrain mobility.

text: Most World War I tanks could travel only at about a walking pace at best. Their steel armour could stop small arms fire and fragments from high-explosive artillery shells. However they were vulnerable to a direct hit from artillery and mortar shells. The environment inside was extremely unpleasant; as ventilation was inadequate the atmosphere was heavy with poisonous carbon monoxide from the engine and firing the weapons, fuel and oil vapours from the engine and cordite fumes from the weapons. Temperatures inside could reach 50°C (122°F). Entire crews lost consciousness inside the tanks, or collapsed when again exposed to fresh air.[7]

text: To counter the danger of bullet splash or fragments knocked off the inside of the hull, the crew wore helmets with goggles and chainmail masks. Gas masks were also standard issue, as they were to all soldiers at this point in the war due to the use of chemical warfare. The side armour of 8 mm initially made them largely immune to small arms fire, but could be penetrated by the recently developed armour-piercing K bullets. There was also the danger of being overrun by infantry and attacked with grenades. The next generation had thicker armour, making them nearly immune to the K bullets. In response, the Germans developed a larger purpose-made anti-tank rifle, and also a Geballte Ladung ("Bunched Charge")—several regular stick grenades bundled together for a much bigger explosion.

text: Engine power was a primary limitation on the tanks; the roughly one hundred horsepower engines gave a power-to-weight ratio of 3.3 hp/ton (2.5 kW/ton). By the end of the 20th century, power-to-weight ratios exceeded 20 hp/ton (15 kW/ton).

text: Many feel that because the British Commander Field Marshal Douglas Haig was himself a horse cavalryman, his command failed to appreciate the value of tanks. In fact, horse cavalry doctrine in World War I was to "follow up a breakthrough with harassing attacks in the rear", but there were no breakthroughs on the Western Front until the tanks came along. Despite these supposed views of Haig, he made an order for 1,000 tanks shortly after the failure at the Somme and always remained firmly in favour of further production.

text: In 1919, Major General Sir Louis Jackson said: "The tank was a freak. The circumstances which called it into existence were exceptional and not likely to recur. If they do, they can be dealt with by other means."[8]

text: French developments[edit]

text: France at the same time developed its own tracked AFVs, but the situation there was very different. In Britain a single committee had coordinated design, and had to overcome the initial resistance of the Army, while the major industries remained passive. Almost all production effort was thus concentrated into the Mark I and its direct successors, all very similar in shape. In France, on the other hand, there were multiple and conflicting lines of development which were badly integrated, resulting in three major and quite disparate production types. A major arms producer, Schneider, took the lead in January 1915 and tried to build a first armoured vehicle based on the Baby Holt tractor but initially the development process was slow until in July they received political, even presidential, support by combining their project with that of a mechanical wire cutter devised by engineer and politician Jean-Louis Bréton. In December 1915, the influential Colonel Estienne made the Supreme Command very enthusiastic about the idea of creating an armoured force based on these vehicles; strong Army support for tanks was a constant during the decades that followed. Already in January and February 1916 quite substantial orders were made, at that moment with a total number of 800 much larger than the British ones.

text: Army enthusiasm and haste had its immediate drawbacks however. As a result of the involvement of inexperienced army officers ordered to devise a new tank based on the larger 75 hp Holt chassis in a very short period of time, the first French tanks were poorly designed with respect to the need to cross trenches and did not take the sponson-mounting route of the British tanks. The first, the Char Schneider CA equipped with a short 75 mm howitzer, had poor mobility due to a short track length combined with a hull that overhung front and rear. It was unreliable as well; a maximum of only about 130 of the 400 built were ever operational at the same time. Then industrial rivalry began to play a detrimental role: it created the heavy Char St Chamond, a parallel development not ordered by the Army but approved by government through industrial lobby, which mounted much more impressive weaponry — its 75 mm was the most powerful gun fielded by any operational tank up till 1941 — but also combined many of the Schneider CA's faults with an even larger overhanging body. Its innovative petro-electrical transmission, while allowing for easy steering, was insufficiently developed and led to a large number of breakdowns.

text: But industrial initiative also led to swift advances. The car industry, already used to vehicle mass production and having much more experience in vehicle layout, in 1916 designed the first practical light tanks, a class largely neglected by the British. It was Renault's excellent small tank design, the FT, incorporating a proper climbing face for the tracks, that was the first tank to incorporate a top-mounted turret with a full 360° traverse capability. In fact the FT was in many respects the first truly 'modern' tank having a layout that has been followed by almost all designs ever since: driver at the front; main armament in a fully rotating turret on top; engine at the rear. Previous models had been "box tanks", with a single crowded space combining the role of engine room, fighting compartment, ammunition stock and driver's cabin. (A very similar Peugeot prototype, with a fixed casemate mounting a short 75mm cannon, was trialled in 1918 but the idea was not pursued). The FT had the largest production run of any tank of the war, with over 3700 built, more numerous than all British tanks combined. That this would happen was at first far from certain; some in the French army lobbied for the alternative mass production of super-heavy tanks. Much design effort was put in this line of development resulting in the gigantic Char 2C, the most complex and technologically advanced tank of its day. Its very complexity ensured it being produced too late to participate in World War I and in the very small number of just ten, but it was the first tank with a three-man turret; the heaviest to enter service until late in World War II and still the largest ever operational.

text: French production at first lagged behind the British. After August 1916 however, British tank manufacture was temporarily halted to wait for better designs, allowing the French to overtake their allies in numbers. When the French used tanks for the first time on 16 April 1917, during the Nivelle Offensive, they had four times more tanks available. But that did not last long as the offensive was a major failure; the Schneiders were badly deployed and suffered 50% losses from German long-range artillery. The Saint-Chamond tanks, first deployed on 5 May, proved to be so badly designed that they were unable to cross the first line of German trenches.

text: German developments[edit]

text: Germany concentrated more on the development of anti-tank weapons than on development of tanks themselves. They only developed one type of tank which saw combat in the war. The A7V Sturmpanzerwagen was designed in 1917 and was used in battle from March 1918. It was manned by a crew of 18, and had eight machine guns and a 57mm cannon. Only 20 A7Vs were produced during the war.

text: Battle of Cambrai[edit]

text: The first battle in which tanks made a great impact was the Battle of Cambrai in 1917. British Colonel J.F.C. Fuller, chief of staff of the Tank Corps, was responsible for the tanks' role in the battle. They made an unprecedented breakthrough but, as ever on the Western front, the opportunity was not exploited. Ironically, it was the soon-to-be-supplanted horse cavalry that had been assigned the task of following up the motorised tank attack.

text: Tanks became more effective as the lesson of the early tanks was absorbed. The British produced the Mark IV in 1917. Similar to the early Marks in appearance, its construction was considered to produce a more reliable machine, the long-barrelled naval guns were shortened (the barrels of the earlier, longer guns were prone to digging in the mud when negotiating obstacles) and armour was increased just enough to defeat the standard German armour-piercing bullet.

text: The continued need for four men to drive the tank was solved with the Mark V which used Wilson's epicyclic gearing in 1918. Also in 1918 the French produced the Renault FT, the result of a co-operation between Estienne and Louis Renault. As mentioned before, it had the innovative turret position, and was operated by two men. At just 8 tons it was half the weight of the Medium A Whippet but the version with the cannon had more firepower. It was conceived for mass production, and the FT became the most produced tank of World War I by a wide margin, with over 3,000 delivered to the French Army. Large numbers were used by the Americans and several were also lent to the British.

text: In July 1918, the French used 480 tanks (mostly FTs) at the Battle of Soissons, and there were even larger assaults planned for 1919. The Entente had hoped to commit over 30,000 tanks to battle in that year.

text: Whippet[edit]

text: Finally, in a preview of later developments, the British developed the Whippet. This tank was specifically designed to exploit breaches in the enemy front with its relatively higher speed (around 8mph vs 3-4mph for the British heavy tanks). The Whippet was faster than most other tanks, although it carried only machine gun armament, meaning it was not suited to combat with armoured vehicles but instead with infantry. Postwar tank designs reflected this trend towards greater tactical mobility.[citation needed]

text: Villers-Bretonneux: Tank against tank[edit]

text: The German General Staff did not have enthusiasm for the tanks, but allowed the development of anti-tank weapons. Regardless, development of a German tank was under way. The only project to be produced and fielded was the A7V, although only twenty were built. The majority of the fifty or so tanks fielded by Germany were captured British vehicles. A7Vs were captured by the Allies, but they were not used, and most ended up being scrapped.

text: The first tank-versus-tank battles took place 24 April 1918. It was an unexpected engagement between three German A7Vs and three British Mk. IVs at Villers-Bretonneux.

text: Fuller's Plan 1919, involving massive use of tanks for an offensive, was never used because the blockade of Germany and the entry of the US brought an end to the war.