romikgosai/squad_modified huggingface dataset:
In a conventional lamp, the evaporated tungsten eventually condenses on the inner surface of the glass envelope, darkening it. For bulbs that contain a vacuum, the darkening is uniform across the entire surface of the envelope. When a filling of inert gas is used, the evaporated tungsten is carried in the thermal convection currents of the gas, depositing preferentially on the uppermost part of the envelope and blackening just that portion of the envelope. An incandescent lamp that gives 93% or less of its initial light output at 75% of its rated life is regarded as unsatisfactory, when tested according to IEC Publication 60064. Light loss is due to filament evaporation and bulb blackening. Study of the problem of bulb blackening led to the discovery of the Edison effect, thermionic emission and invention of the vacuum tube.

Questions and answers:
['
Q: What darkens a conventional bulb over its lifetime?
A: the evaporated tungsten eventually condenses on the inner surface of the glass envelope', '
Q: What is the IEC guideline for an unacceptable level of light loss?
A: An incandescent lamp that gives 93% or less of its initial light output at 75% of its rated life is regarded as unsatisfactory', '
Q: What are the primary causes of light loss?
A: Light loss is due to filament evaporation and bulb blackening', '
Q: Where in the bulb is evaporated tungsten deposited when inert gas is used?
A: on the uppermost part of the envelope', '
Q: Where in the bulb is evaporated tungsten deposited when a vacuum is used?
A: across the entire surface of the envelope']
A very small amount of water vapor inside a light bulb can significantly affect lamp darkening. Water vapor dissociates into hydrogen and oxygen at the hot filament. The oxygen attacks the tungsten metal, and the resulting tungsten oxide particles travel to cooler parts of the lamp. Hydrogen from water vapor reduces the oxide, reforming water vapor and continuing this water cycle. The equivalent of a drop of water distributed over 500,000 lamps will significantly increase darkening. Small amounts of substances such as zirconium are placed within the lamp as a getter to react with any oxygen that may bake out of the lamp components during operation.

Questions and answers:
['
Q: How does water vapor inside a light bulb affect lamp darkening?
A: significantly increase darkening', '
Q: Why does water increase lamp darkening?
A: The oxygen attacks the tungsten metal, and the resulting tungsten oxide particles travel to cooler parts of the lamp.', '
Q: What is an example of a substance that is added to light bulbs to reduce this effect?
A: zirconium', '
Q: How much water is necessary to result in this darkening affect?
A: The equivalent of a drop of water distributed over 500,000 lamps']
The halogen lamp reduces uneven evaporation of the filament and eliminates darkening of the envelope by filling the lamp with a halogen gas at low pressure, rather than an inert gas. The halogen cycle increases the lifetime of the bulb and prevents its darkening by redepositing tungsten from the inside of the bulb back onto the filament. The halogen lamp can operate its filament at a higher temperature than a standard gas filled lamp of similar power without loss of operating life. Such bulbs are much smaller than normal incandescent bulbs, and are widely used where intense illumination is needed in a limited space. Fiber-optic lamps for optical microscopy is one typical application.

Questions and answers:
['
Q: Does the halogen bulp increase, reduce, or have no effect on filament evaporation?
A: reduces', '
Q: How does the halogen bulb decrease darkening over time?
A: by redepositing tungsten from the inside of the bulb back onto the filament', '
Q: Does a halogen bulb operate at a higher or lower temperature than an incandescent?
A: higher', '
Q: How does the size of a halogen bulb compare to an incandescent?
A: bulbs are much smaller than normal incandescent bulbs', '
Q: What is the most common situation when a halogen bulb is used?
A: where intense illumination is needed in a limited space']
A variation of the incandescent lamp did not use a hot wire filament, but instead used an arc struck on a spherical bead electrode to produce heat. The electrode then became incandescent, with the arc contributing little to the light produced. Such lamps were used for projection or illumination for scientific instruments such as microscopes. These arc lamps ran on relatively low voltages and incorporated tungsten filaments to start ionization within the envelope. They provided the intense concentrated light of an arc lamp but were easier to operate. Developed around 1915, these lamps were displaced by mercury and xenon arc lamps.

Questions and answers:
['
Q: What did an alternate version of the incandescent lamp substitute for a wire filament?
A: an arc struck on a spherical bead electrode', '
Q: What was a common application for this type of bulb?
A: scientific instruments such as microscopes', '
Q: When was this style of lamp developed?
A: 1915', '
Q: What displaced this style of lamp?
A: mercury and xenon arc lamps']
Incandescent lamps are nearly pure resistive loads with a power factor of 1. This means the actual power consumed (in watts) and the apparent power (in volt-amperes) are equal. Incandescent light bulbs are usually marketed according to the electrical power consumed. This is measured in watts and depends mainly on the resistance of the filament, which in turn depends mainly on the filament's length, thickness, and material. For two bulbs of the same voltage, type, color, and clarity, the higher-powered bulb gives more light.

Questions and answers:
['
Q: What does a power factor of 1 mean?
A: the actual power consumed (in watts) and the apparent power (in volt-amperes) are equal', '
Q: What principally determines the wattage of an incandescent bulb?
A: the resistance of the filament', "
Q: What determines the resistance of the filament?
A: the filament's length, thickness, and material", '
Q: How close do incandescent lamps come to pure resistive loads?
A: Incandescent lamps are nearly pure resistive loads', '
Q: All other things being equal, how does wattage affect light emitted?
A: the higher-powered bulb gives more light']
The actual resistance of the filament is temperature dependent. The cold resistance of tungsten-filament lamps is about 1/15 the hot-filament resistance when the lamp is operating. For example, a 100-watt, 120-volt lamp has a resistance of 144 ohms when lit, but the cold resistance is much lower (about 9.5 ohms). Since incandescent lamps are resistive loads, simple phase-control TRIAC dimmers can be used to control brightness. Electrical contacts may carry a "T" rating symbol indicating that they are designed to control circuits with the high inrush current characteristic of tungsten lamps. For a 100-watt, 120-volt general-service lamp, the current stabilizes in about 0.10 seconds, and the lamp reaches 90% of its full brightness after about 0.13 seconds.

Questions and answers:
['
Q: What determines the resistance of a filament?
A: temperature', '
Q: What does a "T" rating symbol on an electrical contact mean?
A: they are designed to control circuits with the high inrush current characteristic of tungsten lamps', '
Q: How long does it take a typical 100-watt bulb to achieve 90% of its brightness?
A: 0.13 seconds', '
Q: How does the cold resistance of tungsten filament lamps compare to the hot resistance?
A: The cold resistance of tungsten-filament lamps is about 1/15 the hot-filament resistance', '
Q: What is the resistance of a typical lit 100-watt incandescent bulb?
A: 144 ohms']
Incandescent light bulbs come in a range of shapes and sizes. The names of the shapes may be slightly different in some regions. Many of these shapes have a designation consisting of one or more letters followed by one or more numbers, e.g. A55 or PAR38. The letters represent the shape of the bulb. The numbers represent the maximum diameter, either in 1⁄8 of an inch, or in millimeters, depending on the shape and the region. For example, 63 mm reflectors are designated R63, but in the US, they are known as R20 (2.5 in). However, in both regions, a PAR38 reflector is known as PAR38.

Questions and answers:
['
Q: What do the letters identify in a bulb shape designation?
A: the shape of the bulb', '
Q: What do the numbers identify in a bulb shape designation?
A: the maximum diameter', '
Q: Can the name of a certain bulb shape vary?
A: The names of the shapes may be slightly different in some regions', '
Q: What units are the bulb sizes measured in?
A: 1⁄8 of an inch, or in millimeters']
Very small lamps may have the filament support wires extended through the base of the lamp, and can be directly soldered to a printed circuit board for connections. Some reflector-type lamps include screw terminals for connection of wires. Most lamps have metal bases that fit in a socket to support the lamp and conduct current to the filament wires. In the late 19th century, manufacturers introduced a multitude of incompatible lamp bases. General Electric introduced standard base sizes for tungsten incandescent lamps under the Mazda trademark in 1909. This standard was soon adopted across the US, and the Mazda name was used by many manufacturers under license through 1945. Today most incandescent lamps for general lighting service use an Edison screw in candelabra, intermediate, or standard or mogul sizes, or double contact bayonet base. Technical standards for lamp bases include ANSI standard C81.67 and IEC standard 60061-1 for common commercial lamp sizes, to ensure interchangeablitity between different manufacturer's products. Bayonet base lamps are frequently used in automotive lamps to resist loosening due to vibration. A bipin base is often used for halogen or reflector lamps.

Questions and answers:
['
Q: Which company introduced standard base sizes for incandescent lamps?
A: General Electric', '
Q: In what year were standard base sizes introduced for incandescent lamps?
A: 1909', '
Q: What are some common technical standards for lamp bases?
A: ANSI standard C81.67 and IEC standard 60061-1', '
Q: What is the typical base type for automotive lamps?
A: Bayonet base lamps', '
Q: What is the typical base type for halogen lamps?
A: bipin base']
This means that a 5% reduction in operating voltage will more than double the life of the bulb, at the expense of reducing its light output by about 16%. This may be a very acceptable trade off for a light bulb that is in a difficult-to-access location (for example, traffic lights or fixtures hung from high ceilings). Long-life bulbs take advantage of this trade-off. Since the value of the electric power they consume is much more than the value of the lamp, general service lamps emphasize efficiency over long operating life. The objective is to minimize the cost of light, not the cost of lamps. Early bulbs had a life of up to 2500 hours, but in 1924 a cartel agreed to limit life to 1000 hours. When this was exposed in 1953, General Electric and other leading American manufacturers were banned from limiting the life.

Questions and answers:
['
Q: What level of voltage reduction is required to double the life of an incandescent bulb?
A: a 5% reduction in operating voltage', '
Q: When did light bulb manufacturers establish a cartel to limit bulb life?
A: 1924', '
Q: When did authorities break up the light bulb cartel?
A: 1953', '
Q: What was the artificially low limit on bulb life placed by the cartel?
A: 1000 hours', '
Q: What is an example of a good application for a long-life bulb?
A: difficult-to-access location (for example, traffic lights or fixtures hung from high ceilings)']
The relationships above are valid for only a few percent change of voltage around rated conditions, but they do indicate that a lamp operated at much lower than rated voltage could last for hundreds of times longer than at rated conditions, albeit with greatly reduced light output. The "Centennial Light" is a light bulb that is accepted by the Guinness Book of World Records as having been burning almost continuously at a fire station in Livermore, California, since 1901. However, the bulb emits the equivalent light of a four watt bulb. A similar story can be told of a 40-watt bulb in Texas that has been illuminated since 21 September 1908. It once resided in an opera house where notable celebrities stopped to take in its glow, and was moved to an area museum in 1977.

Questions and answers:
['
Q: When did the "Centennial Light" begin burning?
A: 1901', '
Q: How much light does the bulb emit?
A: the equivalent light of a four watt bulb', '
Q: When did the long-lasting bulb in Texas begin continuing illumination?
A: 21 September 1908', '
Q: Where did the Texas bulb begin its life?
A: an opera house']
In flood lamps used for photographic lighting, the tradeoff is made in the other direction. Compared to general-service bulbs, for the same power, these bulbs produce far more light, and (more importantly) light at a higher color temperature, at the expense of greatly reduced life (which may be as short as two hours for a type P1 lamp). The upper temperature limit for the filament is the melting point of the metal. Tungsten is the metal with the highest melting point, 3,695 K (6,191 °F). A 50-hour-life projection bulb, for instance, is designed to operate only 50 °C (122 °F) below that melting point. Such a lamp may achieve up to 22 lumens per watt, compared with 17.5 for a 750-hour general service lamp.

Questions and answers:
['
Q: At what temperature does a typical 50-hour-life projection bulb operate?
A: 50 °C (122 °F)', '
Q: Which metal has the highest melting point?
A: Tungsten', '
Q: What is the typical life of a P1 lamp?
A: as short as two hours', '
Q: How does the color temperature differ for photographic lighting?
A: higher color temperature']
Lamps designed for different voltages have different luminous efficacy. For example, a 100-watt, 120-volt lamp will produce about 17.1 lumens per watt. A lamp with the same rated lifetime but designed for 230 V would produce only around 12.8 lumens per watt, and a similar lamp designed for 30 volts (train lighting) would produce as much as 19.8 lumens per watt. Lower voltage lamps have a thicker filament, for the same power rating. They can run hotter for the same lifetime before the filament evaporates.

Questions and answers:
['
Q: How many lumens per watt does a typical 100-watt, 120-volt lamp produce?
A: 17.1 lumens per watt', '
Q: How many lumens per watt does a typical train light produce?
A: as much as 19.8 lumens per watt', '
Q: How does filament size relate to voltage level?
A: Lower voltage lamps have a thicker filament', '
Q: What is the effect of a thicker filament on bulb temperature?
A: They can run hotter for the same lifetime before the filament evaporates.']
In addressing the question of who invented the incandescent lamp, historians Robert Friedel and Paul Israel list 22 inventors of incandescent lamps prior to Joseph Swan and Thomas Edison. They conclude that Edison's version was able to outstrip the others because of a combination of three factors: an effective incandescent material, a higher vacuum than others were able to achieve (by use of the Sprengel pump) and a high resistance that made power distribution from a centralized source economically viable.

Questions and answers:
["
Q: What made power distribution economically viable in Edison's lamp?
A: high resistance", '
Q: How many inventors came up with electric lamps before Thomas Edison?
A: 22', '
Q: How did Edison achieve a higher vacuum than other inventors?
A: by use of the Sprengel pump', "
Q: Which historians wrote about the advantages of Edison's lamp over other early versions?
A: Robert Friedel and Paul Israel"]
Physically, clothing serves many purposes: it can serve as protection from the elements, and can enhance safety during hazardous activities such as hiking and cooking. It protects the wearer from rough surfaces, rash-causing plants, insect bites, splinters, thorns and prickles by providing a barrier between the skin and the environment. Clothes can insulate against cold or hot conditions. Further, they can provide a hygienic barrier, keeping infectious and toxic materials away from the body. Clothing also provides protection from harmful UV radiation.

Questions and answers:
['
Q: What can clothing provide during hazardous activities?
A: safety', '
Q: What type of surfaces can clothing protect from?
A: rough', '
Q: What does clothing keep toxic materials away from?
A: body', '
Q: What can insulate against cold or hot conditions?
A: Clothes', '
Q: What type of radiation can clothing provide some protection from?
A: UV']
There is no easy way to determine when clothing was first developed, but some information has been inferred by studying lice. The body louse specifically lives in clothing, and diverge from head lice about 107,000 years ago, suggesting that clothing existed at that time. Another theory is that modern humans are the only survivors of several species of primates who may have worn clothes and that clothing may have been used as long ago as 650 thousand years ago. Other louse-based estimates put the introduction of clothing at around 42,000–72,000 BP.

Questions and answers:
["
Q: What isn't it easy to determine about clothing?
A: when clothing was first developed", '
Q: What organism has provided some information about the timeline of clothing?
A: lice', '
Q: What habitat is the body louse specific to?
A: clothing', '
Q: What may modern humans be the only survivor of several species of?
A: primates', '
Q: How many thousands of years ago may have clothing been worn?
A: 650']
The most obvious function of clothing is to improve the comfort of the wearer, by protecting the wearer from the elements. In hot climates, clothing provides protection from sunburn or wind damage, while in cold climates its thermal insulation properties are generally more important. Shelter usually reduces the functional need for clothing. For example, coats, hats, gloves, and other superficial layers are normally removed when entering a warm home, particularly if one is residing or sleeping there. Similarly, clothing has seasonal and regional aspects, so that thinner materials and fewer layers of clothing are generally worn in warmer seasons and regions than in colder ones.

Questions and answers:
['
Q: What obvious improvement does clothing bestow upon the wearer?
A: comfort', '
Q: In what type of climate does clothing protect against sunburn and wind damage?
A: hot', '
Q: What property of clothing is important in cold climates?
A: thermal insulation', '
Q: What has seasonal and regional aspects?
A: clothing', '
Q: What type of material tends to be worn in warmer seasons?
A: thinner']
Clothing can and has in history been made from a very wide variety of materials. Materials have ranged from leather and furs, to woven materials, to elaborate and exotic natural and synthetic fabrics. Not all body coverings are regarded as clothing. Articles carried rather than worn (such as purses), worn on a single part of the body and easily removed (scarves), worn purely for adornment (jewelry), or those that serve a function other than protection (eyeglasses), are normally considered accessories rather than clothing, as are footwear and hats.

Questions and answers:
['
Q: What variety has there been in the materials of clothing throughout history?
A: very wide', "
Q: What is an article that is carried rather than worn that isn't regarded as clothing?
A: purses", "
Q: Jewelry isn't considered clothing because it's usually worn purely for what reason?
A: adornment", '
Q: What are footwear and hats both considered?
A: accessories', '
Q: What is an example of something that serves a function other than protection?
A: eyeglasses']
Clothing protects against many things that might injure the uncovered human body. Clothes protect people from the elements, including rain, snow, wind, and other weather, as well as from the sun. However, clothing that is too sheer, thin, small, tight, etc., offers less protection. Clothes also reduce risk during activities such as work or sport. Some clothing protects from specific environmental hazards, such as insects, noxious chemicals, weather, weapons, and contact with abrasive substances. Conversely, clothing may protect the environment from the clothing wearer, as with doctors wearing medical scrubs.

Questions and answers:
['
Q: What does clothing protect from things which may injure it?
A: the uncovered human body', '
Q: Rain, snow, and wind are what class of things clothing protects the wearer from?
A: elements', '
Q: Clothing that is too sheer will offer less what?
A: protection', '
Q: What type of hazard is noxious chemicals?
A: environmental', '
Q: What type of clothing do doctors wear to protect their surroundings?
A: medical scrubs']
Humans have shown extreme inventiveness in devising clothing solutions to environmental hazards. Examples include: space suits, air conditioned clothing, armor, diving suits, swimsuits, bee-keeper gear, motorcycle leathers, high-visibility clothing, and other pieces of protective clothing. Meanwhile, the distinction between clothing and protective equipment is not always clear-cut—since clothes designed to be fashionable often have protective value and clothes designed for function often consider fashion in their design. Wearing clothes also has social implications. They cover parts of the body that social norms require to be covered, act as a form of adornment, and serve other social purposes.

Questions and answers:
['
Q: What animal has shown extreme inventiveness in the clothing it has devised?
A: Humans', '
Q: What are space suits an example of a solution to? 
A: environmental hazards', '
Q: What type of implication might a certain type of clothing have?
A: social', '
Q: What value may clothing designed to be fashionable also have?
A: protective', '
Q: Why are some parts of the body covered?
A: social norms']
Although dissertations on clothing and its function appear from the 19th century as colonising countries dealt with new environments, concerted scientific research into psycho-social, physiological and other functions of clothing (e.g. protective, cartage) occurred in the first half of the 20th century, with publications such as J. C. Flügel's Psychology of Clothes in 1930, and Newburgh's seminal Physiology of Heat Regulation and The Science of Clothing in 1949. By 1968, the field of environmental physiology had advanced and expanded significantly, but the science of clothing in relation to environmental physiology had changed little. While considerable research has since occurred and the knowledge-base has grown significantly, the main concepts remain unchanged, and indeed Newburgh's book is still cited by contemporary authors, including those attempting to develop thermoregulatory models of clothing development.

Questions and answers:
['
Q: What century do dissertation on clothing first appear from?
A: 19th', "
Q: What year was J. C. Flügel's Psychology of Clothes published?
A: 1930", "
Q: Whose book entitled Physiology of Heat Regulation and The Science of Clothing was published in 1949?
A: Newburgh's", '
Q: How much had the science of clothing in relation to environmental factors changed by 1968?
A: little', '
Q: What have remained unchanged while the knowledge has grown?
A: the main concepts']