romikgosai/squad_modified huggingface dataset:
Although inefficient, incandescent light bulbs have an advantage in applications where accurate color reproduction is important, since the continuous blackbody spectrum emitted from an incandescent light-bulb filament yields near-perfect color rendition, with a color rendering index of 100 (the best possible). White-balancing is still required to avoid too "warm" or "cool" colors, but this is a simple process that requires only the color temperature in Kelvin as input for modern, digital visual reproduction equipment such as video or still cameras unless it is completely automated. The color-rendering performance of incandescent lights cannot be matched by LEDs or fluorescent lights, although they can offer satisfactory performance for non-critical applications such as home lighting. White-balancing such lights is therefore more complicated, requiring additional adjustments to reduce for example green-magenta color casts, and even when properly white-balanced, the color reproduction will not be perfect.

Questions and answers:
['
Q: What is the purpose of white-balancing?
A: to avoid too "warm" or "cool" colors', '
Q: Of incandescent lights, fluorescent lights and LEDs, which has the best color-rendering performance?
A: incandescent lights', '
Q: What is the color rendering index of an incandescent light?
A: 100', '
Q: Why do incandescent lights have superior color rendering?
A: the continuous blackbody spectrum emitted from an incandescent light-bulb filament', '
Q: What is the highest possible color rendering index score?
A: 100']
There are many non-incandescent light sources, such as the fluorescent lamp, high-intensity discharge lamps and LED lamps, which have higher luminous efficiency, and some have been designed to be retrofitted in fixtures for incandescent lights. These devices produce light by luminescence. These lamps produce discrete spectral lines and do not have the broad "tail" of invisible infrared emissions. By careful selection of which electron energy level transitions are used, and fluorescent coatings which modify the spectral distribution, the spectrum emitted can be tuned to mimic the appearance of incandescent sources, or other different color temperatures of white light. Due to the discrete spectral lines rather than a continuous spectrum, the light is not ideal for applications such as photography and cinematography.

Questions and answers:
['
Q: Do fluorescent lights have a higher or lower luminous efficiency than incandescents?
A: higher', '
Q: How can luminescent light sources be modified to resemble the appearance of incandescents?
A: By careful selection of which electron energy level transitions are used, and fluorescent coatings which modify the spectral distribution', '
Q: Why are luminescent light sources not ideal for photography?
A: Due to the discrete spectral lines rather than a continuous spectrum']
The initial cost of an incandescent bulb is small compared to the cost of the energy it uses over its lifetime. Incandescent bulbs have a shorter life than most other lighting, an important factor if replacement is inconvenient or expensive. Some types of lamp, including incandescent and fluorescent, emit less light as they age; this may be an inconvenience, or may reduce effective lifetime due to lamp replacement before total failure. A comparison of incandescent lamp operating cost with other light sources must include illumination requirements, cost of the lamp and labor cost to replace lamps (taking into account effective lamp lifetime), cost of electricity used, effect of lamp operation on heating and air conditioning systems. When used for lighting in houses and commercial buildings, the energy lost to heat can significantly increase the energy required by a building's air conditioning system. During the heating season heat produced by the bulbs is not wasted, although in most cases it is more cost effective to obtain heat from the heating system. Regardless, over the course of a year a more efficient lighting system saves energy in nearly all climates.

Questions and answers:
["
Q: What appliance requires more energy due to the use of incandescent lighting?
A: a building's air conditioning system", '
Q: Do incandescent lights have a longer or shorter life than other lighting sources?
A: shorter', '
Q: What are some factors to consider in calculating operating costs of lighting?
A: illumination requirements, cost of the lamp and labor cost to replace lamps (taking into account effective lamp lifetime), cost of electricity used', '
Q: Do incandescent lights emit more, less, or the same amount of light as they age?
A: less', "
Q: What is more cost-effective, heat from incandescent bulbs or heat from a building's heating system?
A: heat from the heating system"]
Since incandescent light bulbs use more energy than alternatives such as CFLs and LED lamps, many governments have introduced measures to ban their use, by setting minimum efficacy standards higher than can be achieved by incandescent lamps. Measures to ban light bulbs have been implemented in the European Union, the United States, Russia, Brazil, Argentina, Canada and Australia, among others. In the Europe the EC has calculated that the ban contributes 5 to 10 billion euros to the economy and saves 40 TWh of electricity every year, translating in CO2 emission reductions of 15 million tonnes.

Questions and answers:
['
Q: Do incandescent light bulbs use more or less energy as compared to CFLs and LED lamps?
A: more', '
Q: How much does the incandescent light ban in Europe contribute to the economy each year?
A: 5 to 10 billion euros', '
Q: How much energy does the incandescent light ban in Europe save each year?
A: 40 TWh of electricity', '
Q: How much CO2 emissions does the incandescent light ban in Europe save each year?
A: 15 million tonnes', '
Q: How are laws written that bring about a ban of incandescent light bulbs?
A: by setting minimum efficacy standards higher than can be achieved by incandescent lamps']
Objections to banning the use of incandescent light bulbs include the higher initial cost of alternatives and lower quality of light of fluorescent lamps. Some people have concerns about the health effects of fluorescent lamps. However, even though they contain mercury, the environmental performance of CFLs is much better than that of light bulbs, mostly because they consume much less energy and therefore strongly reduce the environmental impact of power production. LED lamps are even more efficient, and are free of mercury. They are regarded as the best solution in terms of cost effectiveness and robustness.

Questions and answers:
['
Q: Is the environmental performance of CFLs better or worse than that of incandescents?
A: better', '
Q: Which type of light bulbs is considered most cost effective and robust?
A: LED lamps', '
Q: What are some objections to banning incandescent bulbs?
A: higher initial cost of alternatives and lower quality of light of fluorescent lamps', '
Q: What substance in CFL bulbs raises health concerns?
A: mercury', '
Q: Do CFLs consume more, less, or the same amount of energy as incandescent bulbs?
A: much less']
Prompted by legislation in various countries mandating increased bulb efficiency, new "hybrid" incandescent bulbs have been introduced by Philips. The "Halogena Energy Saver" incandescents can produce about 23 lm/W; about 30 percent more efficient than traditional incandescents, by using a reflective capsule to reflect formerly wasted infrared radiation back to the filament from which it can be re-emitted as visible light. This concept was pioneered by Duro-Test in 1980 with a commercial product that produced 29.8 lm/W. More advanced reflectors based on interference filters or photonic crystals can theoretically result in higher efficiency, up to a limit of about 270 lm/W (40% of the maximum efficacy possible). Laboratory proof-of-concept experiments have produced as much as 45 lm/W, approaching the efficacy of compact fluorescent bulbs.

Questions and answers:
['
Q: Which company introduced hybrid incandescent bulbs?
A: Philips', '
Q: How much more efficient are Halogena Energy Saver bulbs compared to incandescents?
A: 30 percent', '
Q: What company first marketed light bulbs using the reflective capsule technique to increase energy efficiency?
A: Duro-Test', '
Q: What is the theoretical maximum efficiency of reflective capsule bulbs?
A: 270 lm/W', '
Q: What is the maximum efficiency of reflective capsule bulbs as tested in labs?
A: 45 lm/W']
Incandescent light bulbs consist of an air-tight glass enclosure (the envelope, or bulb) with a filament of tungsten wire inside the bulb, through which an electric current is passed. Contact wires and a base with two (or more) conductors provide electrical connections to the filament. Incandescent light bulbs usually contain a stem or glass mount anchored to the bulb's base that allows the electrical contacts to run through the envelope without air or gas leaks. Small wires embedded in the stem in turn support the filament and its lead wires.

Questions and answers:
['
Q: What is the name of the air-tight glass enclosure in an incandescent bulb?
A: the envelope', '
Q: What is the filament made of?
A: tungsten wire', "
Q: How many conductors are present in the bulb's base?
A: two (or more)", "
Q: What prevents air or gas leaks from a light bulb?
A: a stem or glass mount anchored to the bulb's base", "
Q: What function do small wires in a light bulb's stem perform?
A: Small wires embedded in the stem in turn support the filament and its lead wires"]
Most light bulbs have either clear or coated glass. The coated glass bulbs have a white powdery substance on the inside called kaolin. Kaolin, or kaolinite, is a white, chalky clay in a very fine powder form, that is blown in and electrostatically deposited on the interior of the bulb. It diffuses the light emitted from the filament, producing a more gentle and evenly distributed light. Manufacturers may add pigments to the kaolin to adjust the characteristics of the final light emitted from the bulb. Kaolin diffused bulbs are used extensively in interior lighting because of their comparatively gentle light. Other kinds of colored bulbs are also made, including the various colors used for "party bulbs", Christmas tree lights and other decorative lighting. These are created by coloring the glass with a dopant; which is often a metal like cobalt (blue) or chromium (green). Neodymium-containing glass is sometimes used to provide a more natural-appearing light.

Questions and answers:
['
Q: What is the powdery substance in coated glass light bulbs?
A: kaolin', '
Q: How is kaolin placed inside a light bulb?
A: blown in and electrostatically deposited', '
Q: What is the effect of a kaolin coating on the light cast?
A: a more gentle and evenly distributed light', '
Q: How are Christmas colored light bulbs created?
A: by coloring the glass with a dopant', '
Q: How does kaolin create a more gentle light?
A: It diffuses the light emitted from the filament']
Many arrangements of electrical contacts are used. Large lamps may have a screw base (one or more contacts at the tip, one at the shell) or a bayonet base (one or more contacts on the base, shell used as a contact or used only as a mechanical support). Some tubular lamps have an electrical contact at either end. Miniature lamps may have a wedge base and wire contacts, and some automotive and special purpose lamps have screw terminals for connection to wires. Contacts in the lamp socket allow the electric current to pass through the base to the filament. Power ratings for incandescent light bulbs range from about 0.1 watt to about 10,000 watts.

Questions and answers:
['
Q: What is the name for a base with one or more contacts at the tip and one at the shell?
A: screw base', '
Q: What is the name for a lamp base with one or more contacts on the base and a shell used as a contact or used only as a mechanical support?
A: bayonet base', '
Q: What is the purpose of contacts in the lamp socket?
A: allow the electric current to pass through the base to the filament', '
Q: What is the range of power ratings for incandescent bulbs?
A: 0.1 watt to about 10,000 watts', '
Q: Which types of lamps use screw terminals for connection to wires?
A: automotive and special purpose lamps']
The role of the gas is to prevent evaporation of the filament, without introducing significant heat losses. For these properties, chemical inertness and high atomic or molecular weight is desirable. The presence of gas molecules knocks the liberated tungsten atoms back to the filament, reducing its evaporation and allowing it to be operated at higher temperature without reducing its life (or, for operating at the same temperature, prolongs the filament life). It however introduces heat losses (and therefore efficiency loss) from the filament, by heat conduction and heat convection.

Questions and answers:
['
Q: What is a potential problem with the use of gas in a light bulb?
A: introduces heat losses (and therefore efficiency loss)', '
Q: What are the ideal chemical properties for the gas in a light bulb?
A: chemical inertness and high atomic or molecular weight', '
Q: What is the purpose of the gas in a light bulb?
A: to prevent evaporation of the filament, without introducing significant heat losses', '
Q: How do gases prevent evaporation of the filament?
A: The presence of gas molecules knocks the liberated tungsten atoms back to the filament']
In manufacturing the glass bulb, a type of "ribbon machine" is used. A continuous ribbon of glass is passed along a conveyor belt, heated in a furnace, and then blown by precisely aligned air nozzles through holes in the conveyor belt into molds. Thus the glass bulbs are created. After the bulbs are blown, and cooled, they are cut off the ribbon machine; a typical machine of this sort produces 50,000 bulbs per hour. The filament and its supports are assembled on a glass stem, which is fused to the bulb. The air is pumped out of the bulb, and the evacuation tube in the stem press is sealed by a flame. The bulb is then inserted into the lamp base, and the whole assembly tested.

Questions and answers:
['
Q: What type of machine manufactures glass light bulbs.
A: ribbon machine', '
Q: How many bulbs does the average ribbon machine produce per hour?
A: 50,000', '
Q: How is the filament attached to the bulb?
A: assembled on a glass stem, which is fused to the bulb', '
Q: How is the evacuation tube sealed?
A: by a flame', '
Q: What blows the glass bulbs into their characteristic shape?
A: precisely aligned air nozzles']
The first successful light bulb filaments were made of carbon (from carbonized paper or bamboo). Early carbon filaments had a negative temperature coefficient of resistance — as they got hotter, their electrical resistance decreased. This made the lamp sensitive to fluctuations in the power supply, since a small increase of voltage would cause the filament to heat up, reducing its resistance and causing it to draw even more power and heat even further. In the "flashing" process, carbon filaments were heated by current passing through them while in an evacuated vessel containing hydrocarbon vapor (usually gasoline). The carbon deposited on the filament by this treatment improved the uniformity and strength of filaments as well as their efficiency. A metallized or "graphitized" filament was first heated in a high-temperature oven before flashing and lamp assembly. This transformed the carbon into graphite which further strengthened and smoothed the filament. This also changed the filament to have a positive temperature coefficient, like a metallic conductor, and helped stabilize the lamp's power consumption, temperature and light output against minor variations in supply voltage.

Questions and answers:
['
Q: What material were the first light bulb filaments made from?
A: carbon', '
Q: What was the primary problem with early carbon filaments?
A: as they got hotter, their electrical resistance decreased', '
Q: What were the positive effects of the flashing process?
A: improved the uniformity and strength of filaments as well as their efficiency', '
Q: What properties of graphite improved the filament?
A: further strengthened and smoothed the filament', "
Q: What are the effects of giving the filament a positive temperature coefficient?
A: helped stabilize the lamp's power consumption, temperature and light output against minor variations in supply voltage"]
In 1902, the Siemens company developed a tantalum lamp filament. These lamps were more efficient than even graphitized carbon filaments and could operate at higher temperatures. Since tantalum metal has a lower resistivity than carbon, the tantalum lamp filament was quite long and required multiple internal supports. The metal filament had the property of gradually shortening in use; the filaments were installed with large loops that tightened in use. This made lamps in use for several hundred hours quite fragile. Metal filaments had the property of breaking and re-welding, though this would usually decrease resistance and shorten the life of the filament. General Electric bought the rights to use tantalum filaments and produced them in the US until 1913.

Questions and answers:
['
Q: What company invented the tantalum light filament?
A: Siemens', '
Q: In what year was the tantalum light filament invented?
A: 1902', '
Q: What were the major advantages of the tantalum light filament?
A: These lamps were more efficient than even graphitized carbon filaments and could operate at higher temperatures.', '
Q: Who purchased the rights to the tantalum light filament from Siemens?
A: General Electric', '
Q: When did GE cease production of the tantalum light filament?
A: 1913']
In 1906, the tungsten filament was introduced. Tungsten metal was initially not available in a form that allowed it to be drawn into fine wires. Filaments made from sintered tungsten powder were quite fragile. By 1910, a process was developed by William D. Coolidge at General Electric for production of a ductile form of tungsten. The process required pressing tungsten powder into bars, then several steps of sintering, swaging, and then wire drawing. It was found that very pure tungsten formed filaments that sagged in use, and that a very small "doping" treatment with potassium, silicon, and aluminium oxides at the level of a few hundred parts per million greatly improved the life and durability of the tungsten filaments.

Questions and answers:
['
Q: What was the problem with manufacturing the tungsten filament?
A: Tungsten metal was initially not available in a form that allowed it to be drawn into fine wires.', '
Q: Who developed the ductile form of tungsten?
A: William D. Coolidge', '
Q: When was the ductile form of tungsten invented?
A: 1910', '
Q: When was the tungsten filament introduced?
A: 1906', '
Q: What other materials were combined with tungsten?
A: potassium, silicon, and aluminium oxides']
To improve the efficiency of the lamp, the filament usually consists of multiple coils of coiled fine wire, also known as a 'coiled coil'. For a 60-watt 120-volt lamp, the uncoiled length of the tungsten filament is usually 22.8 inches (580 mm), and the filament diameter is 0.0018 inches (0.046 mm). The advantage of the coiled coil is that evaporation of the tungsten filament is at the rate of a tungsten cylinder having a diameter equal to that of the coiled coil. The coiled-coil filament evaporates more slowly than a straight filament of the same surface area and light-emitting power. As a result, the filament can then run hotter, which results in a more efficient light source, while reducing the evaporation so that the filament will last longer than a straight filament at the same temperature.

Questions and answers:
['
Q: How long is a typical uncoiled tungsten filament for a 60-watt bulb?
A: 22.8 inches', '
Q: What is the advantage of a coiled-coil filament over a straight filament?
A: The coiled-coil filament evaporates more slowly', '
Q: What positive effects does a slower-evaporating filament enable?
A: more efficient light source', '
Q: What is the typical diameter of the filament on a 60-watt bulb?
A: 0.0018 inches']
One of the problems of the standard electric light bulb is filament notching due to evaporation of the filament. Small variations in resistivity along the filament cause "hot spots" to form at points of higher resistivity; a variation of diameter of only 1% will cause a 25% reduction in service life. These hot spots evaporate faster than the rest of the filament, which increases the resistance at that point—this creates a positive feedback that ends in the familiar tiny gap in an otherwise healthy-looking filament. Irving Langmuir found that an inert gas, instead of vacuum, would retard evaporation. General service incandescent light bulbs over about 25 watts in rating are now filled with a mixture of mostly argon and some nitrogen, or sometimes krypton. Lamps operated on direct current develop random stairstep irregularities on the filament surface which may cut lifespan in half compared to AC operation; different alloys of tungsten and rhenium can be used to counteract the effect.

Questions and answers:
['
Q: What is the negative effect of "hot spots" forming on the filament?
A: a variation of diameter of only 1% will cause a 25% reduction in service life', '
Q: Who discovered that inert gas could slow evaporation?
A: Irving Langmuir', '
Q: Which gases are typically used in a light bulb?
A: argon and some nitrogen, or sometimes krypton', '
Q: Which type of alloys can decrease "stairstep" irregularities in light bulb filaments?
A: alloys of tungsten and rhenium']
While inert gas reduces filament evaporation, it also conducts heat from the filament, thereby cooling the filament and reducing efficiency. At constant pressure and temperature, the thermal conductivity of a gas depends upon the molecular weight of the gas and the cross sectional area of the gas molecules. Higher molecular weight gasses have lower thermal conductivity, because both the molecular weight is higher and also the cross sectional area is higher. Xenon gas improves efficiency because of its high molecular weight, but is also more expensive, so its use is limited to smaller lamps.

Questions and answers:
['
Q: Why does inert gas reduce efficiency?
A: conducts heat from the filament, thereby cooling the filament', '
Q: What affects the thermal conductivity of a gas?
A: molecular weight of the gas and the cross sectional area of the gas molecules', '
Q: How does the molecular weight of a gas relate to thermal conductivity?
A: Higher molecular weight gasses have lower thermal conductivity', '
Q: Why is xenon gas not more widely used?
A: more expensive, so its use is limited to smaller lamps', '
Q: What is the advantage of using inert gas in a light bulb?
A: reduces filament evaporation']
During ordinary operation, the tungsten of the filament evaporates; hotter, more-efficient filaments evaporate faster. Because of this, the lifetime of a filament lamp is a trade-off between efficiency and longevity. The trade-off is typically set to provide a lifetime of several hundred to 2,000 hours for lamps used for general illumination. Theatrical, photographic, and projection lamps may have a useful life of only a few hours, trading life expectancy for high output in a compact form. Long-life general service lamps have lower efficiency but are used where the cost of changing the lamp is high compared to the value of energy used.

Questions and answers:
['
Q: What determines how fast a tungsten filament evaporates?
A: hotter, more-efficient filaments evaporate faster', '
Q: What is the typical goal for the life of a tungsten filament bulb?
A: several hundred to 2,000 hours', '
Q: Which types of lamps may have particularly short lives?
A: Theatrical, photographic, and projection lamps', '
Q: What is the typical tradeoff in light bulb design?
A: efficiency and longevity']