nc33/MultiSpan_SQUAD huggingface dataset:
Incandescent_light_bulb

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.

Question: What is the purpose of white-balancing?
Answer: to avoid too "warm" or "cool" colors

Question: Of incandescent lights, fluorescent lights and LEDs, which has the best color-rendering performance?
Answer: incandescent lights

Question: What is the color rendering index of an incandescent light?
Answer: 100

Question: Why do incandescent lights have superior color rendering?
Answer: the continuous blackbody spectrum emitted from an incandescent light-bulb filament

Question: What is the highest possible color rendering index score?
Answer: 100
Incandescent_light_bulb

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.

Question: Do fluorescent lights have a higher or lower luminous efficiency than incandescents?
Answer: higher

Question: How can luminescent light sources be modified to resemble the appearance of incandescents?
Answer: By careful selection of which electron energy level transitions are used, and fluorescent coatings which modify the spectral distribution

Question: Why are luminescent light sources not ideal for photography?
Answer: Due to the discrete spectral lines rather than a continuous spectrum
Incandescent_light_bulb

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.

Question: What appliance requires more energy due to the use of incandescent lighting?
Answer: a building's air conditioning system

Question: Do incandescent lights have a longer or shorter life than other lighting sources?
Answer: shorter

Question: What are some factors to consider in calculating operating costs of lighting?
Answer: illumination requirements, cost of the lamp and labor cost to replace lamps (taking into account effective lamp lifetime), cost of electricity used

Question: Do incandescent lights emit more, less, or the same amount of light as they age?
Answer: less

Question: What is more cost-effective, heat from incandescent bulbs or heat from a building's heating system?
Answer: heat from the heating system
Incandescent_light_bulb

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.

Question: Do incandescent light bulbs use more or less energy as compared to CFLs and LED lamps?
Answer: more

Question: How much does the incandescent light ban in Europe contribute to the economy each year?
Answer: 5 to 10 billion euros

Question: How much energy does the incandescent light ban in Europe save each year?
Answer: 40 TWh of electricity

Question: How much CO2 emissions does the incandescent light ban in Europe save each year?
Answer: 15 million tonnes

Question: How are laws written that bring about a ban of incandescent light bulbs?
Answer: by setting minimum efficacy standards higher than can be achieved by incandescent lamps
Incandescent_light_bulb

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.

Question: Is the environmental performance of CFLs better or worse than that of incandescents?
Answer: better

Question: Which type of light bulbs is considered most cost effective and robust?
Answer: LED lamps

Question: What are some objections to banning incandescent bulbs?
Answer: higher initial cost of alternatives and lower quality of light of fluorescent lamps

Question: What substance in CFL bulbs raises health concerns?
Answer: mercury

Question: Do CFLs consume more, less, or the same amount of energy as incandescent bulbs?
Answer: much less
Incandescent_light_bulb

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.

Question: Which company introduced hybrid incandescent bulbs?
Answer: Philips

Question: How much more efficient are Halogena Energy Saver bulbs compared to incandescents?
Answer: 30 percent

Question: What company first marketed light bulbs using the reflective capsule technique to increase energy efficiency?
Answer: Duro-Test

Question: What is the theoretical maximum efficiency of reflective capsule bulbs?
Answer: 270 lm/W

Question: What is the maximum efficiency of reflective capsule bulbs as tested in labs?
Answer: 45 lm/W
Incandescent_light_bulb

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.

Question: What is the name of the air-tight glass enclosure in an incandescent bulb?
Answer: the envelope

Question: What is the filament made of?
Answer: tungsten wire

Question: How many conductors are present in the bulb's base?
Answer: two (or more)

Question: What prevents air or gas leaks from a light bulb?
Answer: a stem or glass mount anchored to the bulb's base

Question: What function do small wires in a light bulb's stem perform?
Answer: Small wires embedded in the stem in turn support the filament and its lead wires
Incandescent_light_bulb

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.

Question: What is the name for a base with one or more contacts at the tip and one at the shell?
Answer: screw base

Question: 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?
Answer: bayonet base

Question: What is the purpose of contacts in the lamp socket?
Answer: allow the electric current to pass through the base to the filament

Question: What is the range of power ratings for incandescent bulbs?
Answer: 0.1 watt to about 10,000 watts

Question: Which types of lamps use screw terminals for connection to wires?
Answer: automotive and special purpose lamps
Incandescent_light_bulb

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.

Question: What is a potential problem with the use of gas in a light bulb?
Answer: introduces heat losses (and therefore efficiency loss)

Question: What are the ideal chemical properties for the gas in a light bulb?
Answer: chemical inertness and high atomic or molecular weight

Question: What is the purpose of the gas in a light bulb?
Answer: to prevent evaporation of the filament, without introducing significant heat losses

Question: How do gases prevent evaporation of the filament?
Answer: The presence of gas molecules knocks the liberated tungsten atoms back to the filament
Incandescent_light_bulb

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.

Question: What type of machine manufactures glass light bulbs.
Answer: ribbon machine

Question: How many bulbs does the average ribbon machine produce per hour?
Answer: 50,000

Question: How is the filament attached to the bulb?
Answer: assembled on a glass stem, which is fused to the bulb

Question: How is the evacuation tube sealed?
Answer: by a flame

Question: What blows the glass bulbs into their characteristic shape?
Answer: precisely aligned air nozzles
Incandescent_light_bulb

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.

Question: What material were the first light bulb filaments made from?
Answer: carbon

Question: What was the primary problem with early carbon filaments?
Answer: as they got hotter, their electrical resistance decreased

Question: What were the positive effects of the flashing process?
Answer: improved the uniformity and strength of filaments as well as their efficiency

Question: What properties of graphite improved the filament?
Answer: further strengthened and smoothed the filament

Question: What are the effects of giving the filament a positive temperature coefficient?
Answer: helped stabilize the lamp's power consumption, temperature and light output against minor variations in supply voltage
Incandescent_light_bulb

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.

Question: What company invented the tantalum light filament?
Answer: Siemens

Question: In what year was the tantalum light filament invented?
Answer: 1902

Question: What were the major advantages of the tantalum light filament?
Answer: These lamps were more efficient than even graphitized carbon filaments and could operate at higher temperatures.

Question: Who purchased the rights to the tantalum light filament from Siemens?
Answer: General Electric

Question: When did GE cease production of the tantalum light filament?
Answer: 1913
Incandescent_light_bulb

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.

Question: What was the problem with manufacturing the tungsten filament?
Answer: Tungsten metal was initially not available in a form that allowed it to be drawn into fine wires.

Question: Who developed the ductile form of tungsten?
Answer: William D. Coolidge

Question: When was the ductile form of tungsten invented?
Answer: 1910

Question: When was the tungsten filament introduced?
Answer: 1906

Question: What other materials were combined with tungsten?
Answer: potassium, silicon, and aluminium oxides
Incandescent_light_bulb

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.

Question: How long is a typical uncoiled tungsten filament for a 60-watt bulb?
Answer: 22.8 inches

Question: What is the advantage of a coiled-coil filament over a straight filament?
Answer: The coiled-coil filament evaporates more slowly

Question: What positive effects does a slower-evaporating filament enable?
Answer: more efficient light source

Question: What is the typical diameter of the filament on a 60-watt bulb?
Answer: 0.0018 inches
Incandescent_light_bulb

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.

Question: What is the negative effect of "hot spots" forming on the filament?
Answer: a variation of diameter of only 1% will cause a 25% reduction in service life

Question: Who discovered that inert gas could slow evaporation?
Answer: Irving Langmuir

Question: Which gases are typically used in a light bulb?
Answer: argon and some nitrogen, or sometimes krypton

Question: Which type of alloys can decrease "stairstep" irregularities in light bulb filaments?
Answer: alloys of tungsten and rhenium
Incandescent_light_bulb

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.

Question: Why does inert gas reduce efficiency?
Answer: conducts heat from the filament, thereby cooling the filament

Question: What affects the thermal conductivity of a gas?
Answer: molecular weight of the gas and the cross sectional area of the gas molecules

Question: How does the molecular weight of a gas relate to thermal conductivity?
Answer: Higher molecular weight gasses have lower thermal conductivity

Question: Why is xenon gas not more widely used?
Answer: more expensive, so its use is limited to smaller lamps

Question: What is the advantage of using inert gas in a light bulb?
Answer: reduces filament evaporation
Incandescent_light_bulb

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.

Question: What determines how fast a tungsten filament evaporates?
Answer: hotter, more-efficient filaments evaporate faster

Question: What is the typical goal for the life of a tungsten filament bulb?
Answer: several hundred to 2,000 hours

Question: Which types of lamps may have particularly short lives?
Answer: Theatrical, photographic, and projection lamps

Question: What is the typical tradeoff in light bulb design?
Answer: efficiency and longevity