What is the 4th rail?
fourth rail (plural fourth rails) (rail transport) An extra rail in addition to the third rail (live rail) which is used for current return purposes, mainly by London Underground, because of problems caused by using the running rails for current return underground.
How does 4th rail work?
With top-contact third (and fourth) rail a heavy shoe attached to the underside of a wooden beam which in turn is attached to the bogie, collects power by sliding over the top surface of the conductor rail.
What are the voltages on 4th rail electrification?
The Underground uses a relatively uncommon four rail system of electrification. Two standard gauge rails are the running rails; the outer third rail carries positive current at +420 V DC and the inner fourth rail is the negative return at –210 V DC, giving a supply voltage of 630 V DC.
What happens if you pee on the third rail?
Penile electrocution is very painful. And if the electrical current is sustained, your testicles will explode.” There have been plenty of reports of death while peeing, but few have confirmed that the pee-to-rail contact was the actual cause of death, rather than electrocution for touching a 600-plus-volt line.
Can you touch the third rail?
– The ‘third rail’ looks like a normal railway rail, but is electrified. The electricity is so strong that if you touch the rail, you will be seriously injured or killed. – The third rail and overhead lines have electricity flowing through them at all times and are never switched off.
How are the tracks on the London Underground electrified?
The two bigger ones are for wheels. The lines are electrified with a four-rail DC system: a conductor rail between the rails is energised at −210 V and a rail outside the running rails at +420 V, giving a potential difference of 630 V.
Why does the London Underground have four rails?
The 4th rail system is not needed for tram cars on the high street because tram cars draw for less current than London underground trains. The 3rd rail is the regular current carrier. What does Google know about me? You may know that Google is tracking you, but most people don’t realize the extent of it.
Why are there 4 rails in a rail system?
The 4th rail in electrical rail systems is to prevent stray currents from corroding 3rd party buried services in the vicinity of the railway system such as iron pipes.
How many volts does the London Underground run on?
All of the system runs on 630 volts DC, with the -210 volt negative rail between the running rails and the +420 volt positive rail outside the running rails. The positive rail can be on either side of the track but is positioned furthest from the platform at stations.