Divyanshu67/squad_v2 huggingface dataset:
Neptune

Neptune's more varied weather when compared to Uranus is due in part to its higher internal heating. Although Neptune lies over 50% further from the Sun than Uranus, and receives only 40% its amount of sunlight, the two planets' surface temperatures are roughly equal. The upper regions of Neptune's troposphere reach a low temperature of 51.8 K (−221.3 °C). At a depth where the atmospheric pressure equals 1 bar (100 kPa), the temperature is 72.00 K (−201.15 °C). Deeper inside the layers of gas, the temperature rises steadily. As with Uranus, the source of this heating is unknown, but the discrepancy is larger: Uranus only radiates 1.1 times as much energy as it receives from the Sun; whereas Neptune radiates about 2.61 times as much energy as it receives from the Sun. Neptune is the farthest planet from the Sun, yet its internal energy is sufficient to drive the fastest planetary winds seen in the Solar System. Depending on the thermal properties of its interior, the heat left over from Neptune's formation may be sufficient to explain its current heat flow, though it is more difficult to simultaneously explain Uranus's lack of internal heat while preserving the apparent similarity between the two planets.

Question: Why might Neptune have more varied weather than Uranus?
Answer: higher internal heating

Question: How much farther is Neptune from the Sun than Uranus?
Answer: 50%

Question: How much percentage of the sun does Neptune get compared to Uranus?
Answer: 40%

Question: How much more energy does Neptune radiate than it receives? 
Answer: 2.61

Question: The current heat flow on Neptune might be explained by what?
Answer: heat left over from Neptune's formation

Question: Why might Uranus have more varied weather than Jupiter?

Question:  How much farther is Neptune from the Moon than Uranus?

Question: How much percentage of the sun does Neptune get compared to Jupiter?

Question: How much more energy does Jupiter radiate than it receives?

Question:  The current cold flow on Neptune might be explained by what?
Neptune

On 11 July 2011, Neptune completed its first full barycentric orbit since its discovery in 1846, although it did not appear at its exact discovery position in the sky, because Earth was in a different location in its 365.26-day orbit. Because of the motion of the Sun in relation to the barycentre of the Solar System, on 11 July Neptune was also not at its exact discovery position in relation to the Sun; if the more common heliocentric coordinate system is used, the discovery longitude was reached on 12 July 2011.

Question: When did Neptune complete it's first barycentric orbit since it's discovery?
Answer: 11 July 2011

Question: What is the Earth's orbit?
Answer: 365.26-day

Question: Using the heliocentric coordinate system, when did Neptune reach the discovery longitude? 
Answer: 12 July 2011

Question: Why didn't Neptune appear to be in it's exact discover position? 
Answer: Earth was in a different location

Question: When did Neptune complete it's last barycentric orbit since it's discovery?

Question: Using the heliocentric coordinate system, when did Jupiter reach the discovery longitude?

Question: Why did Neptune appear to be in it's exact discover position?
Neptune

Neptune's orbit has a profound impact on the region directly beyond it, known as the Kuiper belt. The Kuiper belt is a ring of small icy worlds, similar to the asteroid belt but far larger, extending from Neptune's orbit at 30 AU out to about 55 AU from the Sun. Much in the same way that Jupiter's gravity dominates the asteroid belt, shaping its structure, so Neptune's gravity dominates the Kuiper belt. Over the age of the Solar System, certain regions of the Kuiper belt became destabilised by Neptune's gravity, creating gaps in the Kuiper belt's structure. The region between 40 and 42 AU is an example.

Question: What is the region behind Neptune called? 
Answer: Kuiper belt

Question: What does the Kuiper belt consist of?
Answer: small icy worlds

Question: Where is the Kuiper belt relative to Neptune?
Answer: 30 AU out to about 55 AU from the Sun

Question: What dominates the Kuiper belt? 
Answer: Neptune's gravity

Question: What did Neptune's gravity do to Kuiper belt? 
Answer: gaps in the Kuiper belt's structure

Question: What is the region behind Jupiter called?

Question:  What does the Kuiper belt not consist of?

Question:  Where is the Kuiper belt relative to Mars?

Question:  What doesn't dominate the Kuiper belt?

Question:  What did Jupiter's gravity do to Kuiper belt?
Neptune

There do exist orbits within these empty regions where objects can survive for the age of the Solar System. These resonances occur when Neptune's orbital period is a precise fraction of that of the object, such as 1:2, or 3:4. If, say, an object orbits the Sun once for every two Neptune orbits, it will only complete half an orbit by the time Neptune returns to its original position. The most heavily populated resonance in the Kuiper belt, with over 200 known objects, is the 2:3 resonance. Objects in this resonance complete 2 orbits for every 3 of Neptune, and are known as plutinos because the largest of the known Kuiper belt objects, Pluto, is among them. Although Pluto crosses Neptune's orbit regularly, the 2:3 resonance ensures they can never collide. The 3:4, 3:5, 4:7 and 2:5 resonances are less populated.

Question: What is the fraction of the most heavily populated resonance in the Kuiper belt? 
Answer: 2:3 resonance

Question: How many known objects is in the most populated resonance of the Kuiper belt?
Answer: 200

Question: What is the best known, and largest, object in the Kuiper belt?
Answer: Pluto

Question: What is the resonance of Pluto in the Kuiper belt?
Answer: 2:3

Question: Which resonances are less populated in the Kuiper belt?
Answer: 3:4, 3:5, 4:7 and 2:5

Question: What is the fraction of the most heavily populated resonance in the Jupiter belt?

Question: How many unknown objects is in the most populated resonance of the Kuiper belt?

Question:  What is the least known object in the Kuiper belt?

Question:  Which resonances are more populated in the Kuiper belt?

Question:  What is the resonance of Jupiter in the Kuiper belt?
Neptune

Neptune has a number of known trojan objects occupying both the Sun–Neptune L4 and L5 Lagrangian points—gravitationally stable regions leading and trailing Neptune in its orbit, respectively. Neptune trojans can be viewed as being in a 1:1 resonance with Neptune. Some Neptune trojans are remarkably stable in their orbits, and are likely to have formed alongside Neptune rather than being captured. The first and so far only object identified as associated with Neptune's trailing L5 Lagrangian point is 2008 LC18. Neptune also has a temporary quasi-satellite, (309239) 2007 RW10. The object has been a quasi-satellite of Neptune for about 12,500 years and it will remain in that dynamical state for another 12,500 years.

Question: What is the resonance of Neptune trojans?
Answer: 1:1

Question: Where did most Neptune trojans form?
Answer: alongside Neptune

Question: What is the only object identified with Neptune's trailing L5 Lagrangian point?
Answer: 2008 LC18

Question: What is Neptune's temporary quasi-satellite named?
Answer: (309239) 2007 RW10

Question: How long has Neptune's quasi-satellite been with Neptune? 
Answer: 12,500 years

Question:  What is the resonance of Jupiter trojans?

Question:  Where did most Jupiter trojans form?

Question: What isn't the object identified with Neptune's trailing L5 Lagrangian point?

Question:  What is Neptune's temporary  real satellite named?

Question:  How long has Neptune's real satellite been with Neptune?
Neptune

The formation of the ice giants, Neptune and Uranus, has proven difficult to model precisely. Current models suggest that the matter density in the outer regions of the Solar System was too low to account for the formation of such large bodies from the traditionally accepted method of core accretion, and various hypotheses have been advanced to explain their formation. One is that the ice giants were not formed by core accretion but from instabilities within the original protoplanetary disc and later had their atmospheres blasted away by radiation from a nearby massive OB star.

Question: What could have blasted Neptune and Uranus's atmosphere with radiation, aiding in creation? 
Answer: nearby massive OB star

Question: What is too low to account for the formation of Neptune?
Answer: matter density

Question: If Neptune was formed from instabilities within the original protoplanetary disc, what was it not formed by?
Answer: core accretion

Question: What didn't blast Neptune and Uranus's atmosphere with radiation, aiding in creation?

Question:  What is too high to account for the formation of Neptune?

Question:  If Neptune wasn't formed from instabilities within the original protoplanetary disc, what was it formed by?
Neptune

An alternative concept is that they formed closer to the Sun, where the matter density was higher, and then subsequently migrated to their current orbits after the removal of the gaseous protoplanetary disc. This hypothesis of migration after formation is favoured, due to its ability to better explain the occupancy of the populations of small objects observed in the trans-Neptunian region. The current most widely accepted explanation of the details of this hypothesis is known as the Nice model, which explores the effect of a migrating Neptune and the other giant planets on the structure of the Kuiper belt.

Question: If Neptune formed closer to the sun, what is the matter density?
Answer: higher

Question: If Neptune formed closer to the sun, what caused it to migrate to it's current orbit?
Answer: removal of the gaseous protoplanetary disc

Question: What is the most widely accepted explanation of Neptune's formation called?
Answer: the Nice model

Question: What does The Nice model consider effected the migration of Neptune?
Answer: Kuiper belt.

Question: If Jupiter formed closer to the sun, what is the matter density?

Question: If Pluto formed closer to the sun, what caused it to migrate to it's current orbit?

Question: What is the least widely accepted explanation of Neptune's formation called?

Question: What does The Nice model consider effected the migration of Jupiter?
Neptune

Neptune has 14 known moons. Triton is the largest Neptunian moon, comprising more than 99.5% of the mass in orbit around Neptune,[e] and it is the only one massive enough to be spheroidal. Triton was discovered by William Lassell just 17 days after the discovery of Neptune itself. Unlike all other large planetary moons in the Solar System, Triton has a retrograde orbit, indicating that it was captured rather than forming in place; it was probably once a dwarf planet in the Kuiper belt. It is close enough to Neptune to be locked into a synchronous rotation, and it is slowly spiralling inward because of tidal acceleration. It will eventually be torn apart, in about 3.6 billion years, when it reaches the Roche limit. In 1989, Triton was the coldest object that had yet been measured in the Solar System, with estimated temperatures of 38 K (−235 °C).

Question: How many moons does Neptune have?
Answer: 14

Question: What is Neptune's largest moon?
Answer: Triton

Question: Who discovered Triton? 
Answer: William Lassell

Question: What orbit does Triton have around Neptune? 
Answer: retrograde orbit

Question: What does Triton's orbit suggest about it's relation to Neptune?
Answer: that it was captured

Question: What planet has 13 moons?

Question: What is the smallest moon?

Question: Who failed to discover Triton?

Question:  What orbit does Triton have around Jupiter?

Question:  What does Triton's orbit suggest about it's relation to Jupiter?
Neptune

From July to September 1989, Voyager 2 discovered six moons of Neptune. Of these, the irregularly shaped Proteus is notable for being as large as a body of its density can be without being pulled into a spherical shape by its own gravity. Although the second-most-massive Neptunian moon, it is only 0.25% the mass of Triton. Neptune's innermost four moons—Naiad, Thalassa, Despina and Galatea—orbit close enough to be within Neptune's rings. The next-farthest out, Larissa, was originally discovered in 1981 when it had occulted a star. This occultation had been attributed to ring arcs, but when Voyager 2 observed Neptune in 1989, Larissa was found to have caused it. Five new irregular moons discovered between 2002 and 2003 were announced in 2004. A new moon and the smallest yet, S/2004 N 1, was found in 2013. Because Neptune was the Roman god of the sea, Neptune's moons have been named after lesser sea gods.

Question: What discovered six moons of Neptune in 1989?
Answer: Voyager 2

Question: What is the second most massive Neptunian moon? 
Answer: Proteus

Question: What is notable about the moon Proteus?
Answer: irregularly shaped

Question: Which are Neptune's four innermost moons?
Answer: Naiad, Thalassa, Despina and Galatea

Question: When was Neptune's moon Larissa discovered? 
Answer: 1981

Question: What discovered five moons of Neptune in 1989?

Question:  What is the second least massive Neptunian moon?

Question:  What is not notable about the moon Proteus?

Question: Which are Neptune's four outermost moons?

Question: What was discovered in 1984?
Neptune

Because of the distance of Neptune from Earth, its angular diameter only ranges from 2.2 to 2.4 arcseconds, the smallest of the Solar System planets. Its small apparent size makes it challenging to study it visually. Most telescopic data was fairly limited until the advent of Hubble Space Telescope (HST) and large ground-based telescopes with adaptive optics (AO). The first scientifically useful observation of Neptune from ground-based telescopes using adaptive optics, was commenced in 1997 from Hawaii. Neptune is currently entering its spring and summer season and has been shown to be heating up, with increased atmospheric activity and brightness as a consequence. Combined with technological advancements, ground-based telescopes with adaptive optics are recording increasingly more detailed images of this Outer Planet. Both the HST and AO telescopes on Earth has made many new discoveries within the Solar System since the mid-1990s, with a large increase in the number of known satellites and moons around the Outer Planets for example. In 2004 and 2005, five new small satellites of Neptune with diameters between 38 and 61 kilometres were discovered.

Question: What is Neptune's angular diameter range?
Answer: 2.2 to 2.4 arcseconds

Question: The advent of what telescope made it easier to study Neptune?
Answer: Hubble Space Telescope

Question: When was the first useful observation of Neptune from the ground?
Answer: 1997

Question: What seasons are Neptune currently entering?
Answer: spring and summer

Question: What was discovered around Neptune in 2004 and 2005?
Answer: five new small satellites

Question:  What is Neptune's angular height?

Question:  The advent of what telescope made it easier to study Jupiter?

Question: What happened in 1978?

Question:  What seasons are Uranus currently entering?

Question:  What was discovered around Neptune in 2008 and 2009?
Railway_electrification_system

A railway electrification system supplies electric power to railway trains and trams without an on-board prime mover or local fuel supply. Electrification has many advantages but requires significant capital expenditure. Selection of an electrification system is based on economics of energy supply, maintenance, and capital cost compared to the revenue obtained for freight and passenger traffic. Different systems are used for urban and intercity areas; some electric locomotives can switch to different supply voltages to allow flexibility in operation.

Question: What is of the factors the capital cost of electrification system depends on?
Answer: maintenance

Question: How do some locomotives function in order to be more flexible in operation?
Answer: can switch to different supply voltages

Question: What is the main disadvantage of railway electrification?
Answer: significant capital expenditure

Question: What are two types of revenue obtained through railway transportation?
Answer: freight and passenger traffic

Question: What system supplies nuclear power to railway trains?

Question: What requires insignificant capital expenditure?

Question: The same systems are used for both urban and intercity what?

Question: All electric locomotives can switch to different supply voltages to allow for what?

Question: A railway electrification system supplies power to trains and trams with an on-board what?
Railway_electrification_system

Electric railways use electric locomotives to haul passengers or freight in separate cars or electric multiple units, passenger cars with their own motors. Electricity is typically generated in large and relatively efficient generating stations, transmitted to the railway network and distributed to the trains. Some electric railways have their own dedicated generating stations and transmission lines but most purchase power from an electric utility. The railway usually provides its own distribution lines, switches and transformers.

Question: What is used to haul passengers cars?
Answer: electric locomotives

Question: How is electricity being generated for electric locomotives?
Answer: generating stations

Question: What entity provides distribution lines, switches and transformers?
Answer: railway

Question: Which railways haul passengers and freight in the same cars?

Question: What is typically generated in small generating stations?

Question: All electric railways have their own dedicated what?

Question: Very few purchase power from whom?

Question: What is generated in relatively inefficient stations?
Railway_electrification_system

In comparison to the principal alternative, the diesel engine, electric railways offer substantially better energy efficiency, lower emissions and lower operating costs. Electric locomotives are usually quieter, more powerful, and more responsive and reliable than diesels. They have no local emissions, an important advantage in tunnels and urban areas. Some electric traction systems provide regenerative braking that turns the train's kinetic energy back into electricity and returns it to the supply system to be used by other trains or the general utility grid. While diesel locomotives burn petroleum, electricity is generated from diverse sources including many that do not produce carbon dioxide such as nuclear power and renewable forms including hydroelectric, geothermal, wind and solar.

Question: What is the principal alternative to electric railways?
Answer: diesel engine

Question: What locomotives are usually more reliable?
Answer: Electric locomotives

Question: What do some electric traction systems provide?
Answer: regenerative braking

Question: What type of fuel do diesel locomotives use?
Answer: petroleum

Question: What is one of the sources electricity is being generated from?
Answer: geothermal

Question: What does not offer better emissions efficiency?

Question: Electricity is generated from many sources that do produce carbon what?

Question: electricity is generated from non-renewable forms including?

Question: Which locomotives have no global emissions?

Question: All electric traction systems provide what kind of braking?
Railway_electrification_system

Disadvantages of electric traction include high capital costs that may be uneconomic on lightly trafficked routes; a relative lack of flexibility since electric trains need electrified tracks or onboard supercapacitors and charging infrastructure at stations; and a vulnerability to power interruptions. Different regions may use different supply voltages and frequencies, complicating through service. The limited clearances available under catenaries may preclude efficient double-stack container service. The lethal voltages on contact wires and third rails are a safety hazard to track workers, passengers and trespassers. Overhead wires are safer than third rails, but they are often considered unsightly.

Question: What issue can complicate electric railway service?
Answer: different supply voltages and frequencies,

Question: What is a safety hazard to track workers?
Answer: voltages on contact wires

Question: What is a safer alternative to third rails?
Answer: Overhead wires

Question: Why overhead wires are not being widely used?
Answer: considered unsightly.

Question: Advantages of electric traction include?

Question: All regions use the same supply voltages and?

Question: Lethal voltages on contact wires and third rails are non a safety hazard for whom?

Question: Third rails are considered safer than overhead wires, but are considered what?
Railway_electrification_system

Railways must operate at variable speeds. Until the mid 1980s this was only practical with the brush-type DC motor, although such DC can be supplied from an AC catenary via on-board electric power conversion. Since such conversion was not well developed in the late 19th century and early 20th century, most early electrified railways used DC and many still do, particularly rapid transit (subways) and trams. Speed was controlled by connecting the traction motors in various series-parallel combinations, by varying the traction motors' fields, and by inserting and removing starting resistances to limit motor current.

Question: What is speed limit for railways?
Answer: variable speeds

Question: Why is DC motor being used more than AC type?
Answer: conversion was not well developed

Question: What are two types of railway transportation still use DC motor?
Answer: rapid transit (subways) and trams

Question: What must operate at constant speeds?

Question: Speed was controlled by disconnecting the traction motors where?

Question: A brush-type BC motor operated at what speeds?

Question: All early electrified motors used what type of motor?

Question: Varying the transition motors' fields helped control what?
Railway_electrification_system

Motors have very little room for electrical insulation so they generally have low voltage ratings. Because transformers (prior to the development of power electronics) cannot step down DC voltages, trains were supplied with a relatively low DC voltage that the motors can use directly. The most common DC voltages are listed in the previous section. Third (and fourth) rail systems almost always use voltages below 1 kV for safety reasons while overhead wires usually use higher voltages for efficiency. ("Low" voltage is relative; even 600 V can be instantly lethal when touched.)

Question: Why do motors have little space for insulation?
Answer: low voltage ratings

Question: What is most common volatage range used by railway system?
Answer: below 1 kV

Question: Why 1kV voltage is almost always used by rail systems?
Answer: safety reasons

Question: Which system uses higher voltages?
Answer: overhead wires

Question: Is "low" voltage used by trains safe for people?
Answer: lethal

Question: How many volts can be considered nonlethal when touched?

Question: Motors have a lot of room for electrical what?

Question: What can step down DC voltages?

Question: Fifth (and sixth) railsystems use what voltages for safety reasons?

Question: What has high voltage ratings?
Railway_electrification_system

There has, however, been interest among railroad operators in returning to DC use at higher voltages than previously used. At the same voltage, DC often has less loss than AC, and for this reason high-voltage direct current is already used on some bulk power transmission lines. DC avoids the electromagnetic radiation inherent with AC, and on a railway this also reduces interference with signalling and communications and mitigates hypothetical EMF risks. DC also avoids the power factor problems of AC. Of particular interest to railroading is that DC can supply constant power with a single ungrounded wire. Constant power with AC requires three-phase transmission with at least two ungrounded wires. Another important consideration is that mains-frequency 3-phase AC must be carefully planned to avoid unbalanced phase loads. Parts of the system are supplied from different phases on the assumption that the total loads of the 3 phases will even out. At the phase break points between regions supplied from different phases, long insulated supply breaks are required to avoid them being shorted by rolling stock using more than one pantograph at a time. A few railroads have tried 3-phase but its substantial complexity has made single-phase standard practice despite the interruption in power flow that occurs twice every cycle. An experimental 6 kV DC railway was built in the Soviet Union.

Question: What type of electric power garantees lesser loss?
Answer: DC

Question: Which type of supply for electric motors creates electromagnetic radiation?
Answer: AC

Question: What can electromagnetic radiation interfere with?
Answer: signalling and communications

Question: Which type of power does require three-phase transmission?
Answer: AC

Question: Where was an experimental 6kV DC railway built?
Answer: the Soviet Union

Question: Railroad operators have shown little interest in returning to what?

Question: What is being used on all bulk power transmission lines?

Question: DC can supply variable power with a single underground what?

Question: What requires a four-phase transmission with at least two underground wires?

Question: How many railroads have tried 4-phase?
Railway_electrification_system

1,500 V DC is used in the Netherlands, Japan, Republic Of Indonesia, Hong Kong (parts), Republic of Ireland, Australia (parts), India (around the Mumbai area alone, has been converted to 25 kV AC like the rest of India), France (also using 25 kV 50 Hz AC), New Zealand (Wellington) and the United States (Chicago area on the Metra Electric district and the South Shore Line interurban line). In Slovakia, there are two narrow-gauge lines in the High Tatras (one a cog railway). In Portugal, it is used in the Cascais Line and in Denmark on the suburban S-train system.

Question: What is most common voltage for DC supply?
Answer: 1,500 V

Question: How many narrow-gauge lines in Slovakia?
Answer: two

Question: What railway line is DC being used in Portugal?
Answer: the Cascais Line

Question: Where in India line has been converted to AC?
Answer: Mumbai area

Question: In Romania, there are two narrow-gauge lines where?

Question: There is a hog railway located where?

Question: The Cascade Line is located where?

Question: 1,500 V DC is used in what district in Connecticut?

Question: The South Shore Line suburb line uses what?
Railway_electrification_system

3 kV DC is used in Belgium, Italy, Spain, Poland, the northern Czech Republic, Slovakia, Slovenia, South Africa, Chile, and former Soviet Union countries (also using 25 kV 50 Hz AC). It was formerly used by the Milwaukee Road from Harlowton, Montana to Seattle-Tacoma, across the Continental Divide and including extensive branch and loop lines in Montana, and by the Delaware, Lackawanna & Western Railroad (now New Jersey Transit, converted to 25 kV AC) in the United States, and the Kolkata suburban railway (Bardhaman Main Line) in India, before it was converted to 25 kV 50 Hz AC.

Question: What voltage is being used in railway system of South Africa and Chile?
Answer: 3 kV DC

Question: Besides using 3kV DC what other power type is used in the former Soviet Union countries?
Answer: 25 kV 50 Hz AC

Question: What was New Jersey Transit called before?
Answer: Western Railroad

Question: What does the railway system of US use DC or AC?
Answer: AC

Question: What was formally used by the Mississippi Road?

Question: What is used by the current Soviet Union countries?

Question: New York transit in the United States uses what?

Question: The Kukuburra suburban railway is located where?

Question: The Kolkata suburban railway in India converted from what?
Railway_electrification_system

Most electrification systems use overhead wires, but third rail is an option up to about 1,200 V. Third rail systems exclusively use DC distribution. The use of AC is not feasible because the dimensions of a third rail are physically very large compared with the skin depth that the alternating current penetrates to (0.3 millimetres or 0.012 inches) in a steel rail). This effect makes the resistance per unit length unacceptably high compared with the use of DC. Third rail is more compact than overhead wires and can be used in smaller-diameter tunnels, an important factor for subway systems.

Question: What type is mostly used third rail or overhead wires?
Answer: overhead wires

Question: Is trird rail system being used exclusively with AC or DC ?
Answer: DC distribution

Question: What depth does the alternating current penetrate in a steel rail?
Answer: skin depth

Question: What is physically more compact tird rail or overhead wires?
Answer: Third rail

Question: What is more prefferable for subway lines?
Answer: Third rail

Question: All electrical systems use what kind of wires?

Question: The third rail operates over what voltage?

Question: Overhead wires are more compact than third rail and can be used for what?

Question: What is considered an unimportant factor for subway systems?

Question: Overhead wires are considered physically very what?
Railway_electrification_system

DC systems (especially third-rail systems) are limited to relatively low voltages and this can limit the size and speed of trains and cannot use low-level platform and also limit the amount of air-conditioning that the trains can provide. This may be a factor favouring overhead wires and high-voltage AC, even for urban usage. In practice, the top speed of trains on third-rail systems is limited to 100 mph (160 km/h) because above that speed reliable contact between the shoe and the rail cannot be maintained.

Question: Why DC system can effect the speed of trains?
Answer: low voltages

Question: Can DC systems use low-level platform?
Answer: cannot

Question: Besides speed and size what else the low voltage of DC system can effect?
Answer: air-conditioning

Question: What is the speed limit for third rail system trains?
Answer: 160 km/h

Question: What can become unreliable if the speed exceeds the limit of 100 mph for DC system trains?
Answer: contact between the shoe and the rail

Question: DC systems are limited to relatively high what?

Question: The lowest speed of trains on third-rail systems is limited to what?

Question: Above what speed can reliable contact between the shoe and the rail be maintained?

Question: What can not limit the size and speed of trains?

Question: What is not a factor favoring overhead wires and high-voltage AC?
Railway_electrification_system

Some street trams (streetcars) used conduit third-rail current collection. The third rail was below street level. The tram picked up the current through a plough (U.S. "plow") accessed through a narrow slot in the road. In the United States, much (though not all) of the former streetcar system in Washington, D.C. (discontinued in 1962) was operated in this manner to avoid the unsightly wires and poles associated with electric traction. The same was true with Manhattan's former streetcar system. The evidence of this mode of running can still be seen on the track down the slope on the northern access to the abandoned Kingsway Tramway Subway in central London, United Kingdom, where the slot between the running rails is clearly visible, and on P and Q Streets west of Wisconsin Avenue in the Georgetown neighborhood of Washington DC, where the abandoned tracks have not been paved over. The slot can easily be confused with the similar looking slot for cable trams/cars (in some cases, the conduit slot was originally a cable slot). The disadvantage of conduit collection included much higher initial installation costs, higher maintenance costs, and problems with leaves and snow getting in the slot. For this reason, in Washington, D.C. cars on some lines converted to overhead wire on leaving the city center, a worker in a "plough pit" disconnecting the plough while another raised the trolley pole (hitherto hooked down to the roof) to the overhead wire. In New York City for the same reasons of cost and operating efficiency outside of Manhattan overhead wire was used. A similar system of changeover from conduit to overhead wire was also used on the London tramways, notably on the southern side; a typical changeover point was at Norwood, where the conduit snaked sideways from between the running rails, to provide a park for detached shoes or ploughs.

Question: What is the other name for the street trams?
Answer: streetcars

Question: Where is third rail situated in the street trams system?
Answer: below street level

Question: What area in US discontinued using overhead wires for streetcars in 1962?
Answer: Washington, D.C.

Question: What external and weather factors can effect conduit slot?
Answer: leaves and snow

Question: What are the main reasons the conduit lines were converted to overhead  wire system?
Answer: cost and operating efficiency

Question: All street trams use conduit what?

Question: What is accessed through a wide slot in the road?

Question: In what neighborhood in New York have the abandoned tracks not been paved over?

Question: An advantage of conduit collection is much high what?

Question: Cars on all lines have been converted to overhead wire in what city?
Railway_electrification_system

A new approach to avoiding overhead wires is taken by the "second generation" tram/streetcar system in Bordeaux, France (entry into service of the first line in December 2003; original system discontinued in 1958) with its APS (alimentation par sol – ground current feed). This involves a third rail which is flush with the surface like the tops of the running rails. The circuit is divided into segments with each segment energized in turn by sensors from the car as it passes over it, the remainder of the third rail remaining "dead". Since each energized segment is completely covered by the lengthy articulated cars, and goes dead before being "uncovered" by the passage of the vehicle, there is no danger to pedestrians. This system has also been adopted in some sections of the new tram systems in Reims, France (opened 2011) and Angers, France (also opened 2011). Proposals are in place for a number of other new services including Dubai, UAE; Barcelona, Spain; Florence, Italy; Marseille, France; Gold Coast, Australia; Washington, D.C., U.S.A.; Brasília, Brazil and Tours, France.

Question: What year the "second generation" of tram system began to operate in France?
Answer: 2003

Question: When was the original system discontinued?
Answer: 1958

Question: How is the circuit of the third rail divided?
Answer: energized segment

Question: Does energized segment of third rail pose the threat to pedestrians if uncovered?
Answer: no danger

Question: An old approach to avoiding overhead wires is taken by what system?

Question: What system has been adopted in all sections of the new tram systems in Reims, France?

Question: When did the new tram system in Paris, France open?

Question: When did the new trans system in Achnor, France open?

Question: The circuit is left undivided in what system?
Railway_electrification_system

The London Underground in England is one of the few networks that uses a four-rail system. The additional rail carries the electrical return that, on third rail and overhead networks, is provided by the running rails. On the London Underground, a top-contact third rail is beside the track, energized at +420v DC, and a top-contact fourth rail is located centrally between the running rails at −210v DC, which combine to provide a traction voltage of 630v DC. London Underground is now upgrading its fourth rail system to 750v DC with a positive conductor rail energised to +500v DC and a negative conductor rail energised to -250v DC. However, many older sections in tunnels are still energised to 630v DC. The same system was used for Milan's earliest underground line, Milan Metro's line 1, whose more recent lines use an overhead catenary or a third rail.

Question: What type of system does London Underground use?
Answer: four-rail system

Question: What is the purpose of the forth rail?
Answer: carries the electrical return

Question: What is the volatage surge of the third rail of London Underground system?
Answer: +420v DC

Question: What is the voltage of the return rail?
Answer: −210v DC

Question: Where was the system similar to London Underground used as well?
Answer: Milan

Question: Which system in England is one of the few to use a five-rail system?

Question: On the London Underground, a bottom-contact rail is located where?

Question: A bottom-contact fourth rail is located where?

Question: Which system is now upgrading their fifth rail system to 750v DC?

Question: Many newer sections in tunnels are energised to what voltage?
Railway_electrification_system

The key advantage of the four-rail system is that neither running rail carries any current. This scheme was introduced because of the problems of return currents, intended to be carried by the earthed (grounded) running rail, flowing through the iron tunnel linings instead. This can cause electrolytic damage and even arcing if the tunnel segments are not electrically bonded together. The problem was exacerbated because the return current also had a tendency to flow through nearby iron pipes forming the water and gas mains. Some of these, particularly Victorian mains that predated London's underground railways, were not constructed to carry currents and had no adequate electrical bonding between pipe segments. The four-rail system solves the problem. Although the supply has an artificially created earth point, this connection is derived by using resistors which ensures that stray earth currents are kept to manageable levels. Power-only rails can be mounted on strongly insulating ceramic chairs to minimise current leak, but this is not possible for running rails which have to be seated on stronger metal chairs to carry the weight of trains. However, elastomeric rubber pads placed between the rails and chairs can now solve part of the problem by insulating the running rails from the current return should there be a leakage through the running rails.

Question: What is the crucial advantage of four-rail system?
Answer: running rail carries any current

Question: What danger can return currents cause?
Answer: electrolytic damage

Question: How did return current effect water and gas in iron pipes?
Answer: water and gas mains

Question: How are stray earth currents kept to a manageable levels? 
Answer: by using resistors

Question: What insures minimal current leak during power rails instalation?
Answer: ceramic chairs

Question: What is a key advantage to the fifth rail system?

Question: What can happen if the tunnel segments are electrically bonded together?

Question: What has a tendency to flow past nearby iron pipes forming the water and gas mains?

Question: What has a naturally created earth point?

Question: What does not have to be seated on stronger metal chairs?
Railway_electrification_system

On tracks that London Underground share with National Rail third-rail stock (the Bakerloo and District lines both have such sections), the centre rail is connected to the running rails, allowing both types of train to operate, at a compromise voltage of 660 V. Underground trains pass from one section to the other at speed; lineside electrical connections and resistances separate the two types of supply. These routes were originally solely electrified on the four-rail system by the LNWR before National Rail trains were rewired to their standard three-rail system to simplify rolling stock use.

Question: What is the voltage shared two types of trains UK railroad system?
Answer: 660 V

Question: Why some sections of Bakerloo and District lines were rewired to three-rail system?
Answer: to simplify rolling stock use

Question: How did it become possible to share the voltage for different types of train?
Answer: the centre rail is connected to the running rails

Question: What joins the two types of supply?

Question: What was rewired to the standard four-rail system?

Question: What is the maximum voltage of the two UK rail systems?

Question: Above ground trains pass from one section to the other at what?

Question: The London Underground does not share tracks with whom?
Railway_electrification_system

A few lines of the Paris Métro in France operate on a four-rail power scheme because they run on rubber tyres which run on a pair of narrow roadways made of steel and, in some places, concrete. Since the tyres do not conduct the return current, the two guide rails provided outside the running 'roadways' double up as conductor rails, so at least electrically it is a four-rail scheme. One of the guide rails is bonded to the return conventional running rails situated inside the roadway so a single polarity supply is required. The trains are designed to operate from either polarity of supply, because some lines use reversing loops at one end, causing the train to be reversed during every complete journey. The loop was originally provided to save the original steam locomotives having to 'run around' the rest of the train saving much time. Today, the driver does not have to change ends at termini provided with such a loop, but the time saving is not so significant as it takes almost as long to drive round the loop as it does to change ends. Many of the original loops have been lost as lines were extended.

Question: Why some lines of Paris Metro have to operate on a four-rail system?
Answer: rubber tyres

Question: What was the solution for the return current problem in Paris Metro?
Answer: two guide rails

Question: What is required in order for the guide rails to operate properly?
Answer: a single polarity supply

Question: How train is able to turn around after each completed journey?
Answer: reversing loops

Question: Why was the reversing loop created?
Answer: having to 'run around' the rest of the train

Question: All lines of the Paris Metro in France operate on what?

Question: What runs on metal tyres?

Question: Why were many of the original loops kept?

Question: What type of tyres conduct the return current?

Question: What runs on a pair of wide roadways made of steel?
Railway_electrification_system

An early advantage of AC is that the power-wasting resistors used in DC locomotives for speed control were not needed in an AC locomotive: multiple taps on the transformer can supply a range of voltages. Separate low-voltage transformer windings supply lighting and the motors driving auxiliary machinery. More recently, the development of very high power semiconductors has caused the classic "universal" AC/DC motor to be largely replaced with the three-phase induction motor fed by a variable frequency drive, a special inverter that varies both frequency and voltage to control motor speed. These drives can run equally well on DC or AC of any frequency, and many modern electric locomotives are designed to handle different supply voltages and frequencies to simplify cross-border operation.

Question: What was a disadvantage of DC system?
Answer: power-wasting resistors

Question: How can different range of voltages be supplied for AC locomotives?
Answer: multiple taps on the transformer

Question: What taps can provide lighting supply?
Answer: low-voltage transformer windings

Question: What will AC/DC motor be replaced with?
Answer: three-phase induction motor

Question: What is the main advantage of an induction motor?
Answer: can run equally well on DC or AC of any frequency

Question: What was an early disadvantage of AC?

Question: One taps on the transformer can supply what?

Question: The development of low power semiconductors caused what?

Question: No modern electric locomotives are designed to handle what?

Question: Combined low-voltage transformer windings supply what?
Railway_electrification_system

DC commutating electric motors, if fitted with laminated pole pieces, become universal motors because they can also operate on AC; reversing the current in both stator and rotor does not reverse the motor. But the now-standard AC distribution frequencies of 50 and 60 Hz caused difficulties with inductive reactance and eddy current losses. Many railways chose low AC frequencies to overcome these problems. They must be converted from utility power by motor-generators or static inverters at the feeding substations or generated at dedicated traction powerstations.

Question: How can DC motor turn universal?
Answer: if fitted with laminated pole pieces

Question: What problems did AC distribution cause?
Answer: inductive reactance and eddy current losses

Question: How do railways try to solve the problem of inductive reactance of AC system?
Answer: low AC frequencies

Question: How can low frequencies be obtained?
Answer: converted from utility power

Question: Reversing the current in both stator and rotor also reverses what?

Question: Many railways choose high AC frequencies to overcome what?

Question: The now-standard DC frequencies are what?

Question: The distribution frequencies of 60 and 70 Hz caused what?

Question: Many railways choose low DC what?
Railway_electrification_system

High-voltage AC overhead systems are not only for standard gauge national networks. The meter gauge Rhaetian Railway (RhB) and the neighbouring Matterhorn Gotthard Bahn (MGB) operate on 11 kV at 16.7 Hz frequency. Practice has proven that both Swiss and German 15 kV trains can operate under these lower voltages. The RhB started trials of the 11 kV system in 1913 on the Engadin line (St. Moritz-Scuol/Tarasp). The MGB constituents Furka-Oberalp-Bahn (FO) and Brig-Visp-Zermatt Bahn (BVZ) introduced their electric services in 1941 and 1929 respectively, adopting the already proven RhB system.

Question: How did non-standard gauge trains start to operate with high-voltage AC?
Answer: adopting the already proven RhB system.

Question: When was the first trail of RhB system tested?
Answer: 1913

Question: Low-voltage AC overhead systems are not only for what?

Question: Which European trains can operate under high voltages?

Question: The MAB consisted of whom?

Question: Who started trials of the 111kV system?

Question: When did the RhB start trials of the 11 kV system on the Rhaetian line?
Railway_electrification_system

In the United States, 25 Hz, a once-common industrial power frequency is used on Amtrak's 25 Hz traction power system at 12 kV on the Northeast Corridor between Washington, D.C. and New York City and on the Keystone Corridor between Harrisburg, Pennsylvania and Philadelphia. SEPTA's 25 Hz traction power system uses the same 12 kV voltage on the catenary in Northeast Philadelphia. This allows for the trains to operate on both the Amtrak and SEPTA power systems. Apart from having an identical catenary voltage, the power distribution systems of Amtrak and SEPTA are very different. The Amtrak power distribution system has a 138 kV transmission network that provides power to substations which then transform the voltage to 12 kV to feed the catenary system. The SEPTA power distribution system uses a 2:1 ratio autotransformer system, with the catenary fed at 12 kV and a return feeder wire fed at 24 kV. The New York, New Haven and Hartford Railroad used an 11 kV system between New York City and New Haven, Connecticut which was converted to 12.5 kV 60 Hz in 1987.

Question: What frequency was typically used on US Amtrak?
Answer: 25 Hz

Question: What voltage does SEPTA system use?
Answer: 12 kV voltage

Question: What specification is similar for both Amtrak and Septa systems?
Answer: catenary voltage

Question: When was a 11kV system of NY, New Haven and Hartford was converted to 12.5 kV?
Answer: 1987

Question: The Northeast Corridor connects Harrisburg, Pennsylvania and what city?

Question: The Keystone Corridor connects Washington, D.C. and what city?

Question: What uses a 1:2 ratio autotransformer?

Question: When was the New York, New Haven and Hartford railroad converted to a 11 kV system?

Question: What uses a catenary fed at 24 kV?