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

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

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

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

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

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

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

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

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: 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 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 more prefferable for subway lines?
Answer: Third rail

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

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

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

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

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

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

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

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

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: 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: 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: 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: When was overhead wires system being used for the first time in UK?
Answer: 1 December 1909

Question: What line used the overhead wire system first Victoria to Crystal Palace or Peckham Rye to West Noorwood?
Answer: Victoria to Crystal Palace

Question: What was the cause of lines not being extended?
Answer: the First World War

Question: What voltage was used in the two lines opened in 1925 of Southern Railway?
Answer: 6.7 kV 25 Hz

Question: What countries  used three-phase AC system in the the beginning of 20th century?
Answer: Italy, Switzerland and the United States

Question: What country was a bigger user compare to the three of them?
Answer: Italy

Question: Where did Italy start using the AC system?
Answer: in the mountainous regions of northern Italy

Question: How long did the AC system last in northern Italy?
Answer: 1901 until 1976

Question: How long did three-phase system operate in Cascade Tunnel?
Answer: 1909 to 1927

Question: What country has first tried to use single-phase AC?
Answer: Hungary

Question: What frequency did the line of Hungarian rail system used in 1923?
Answer: 16 kV at 50 Hz