Why do the people sitting in the train does not get electric shock?

Answer 1

If the track is fed by overhead power lines then the track is the return path for the electric current and is at earth potential.That is 0 volts

In the UK we use a Third rail system which is raised up,and to one side of the rail.This rail is laid on china insulators and has a voltage of 750volt DC:- very dangerous since if you touch it it tends to clamp muscles on to it.

Answer 2

To get an electric shock, you need to have a difference in voltage between the parts of your body that are in contact with the parts of an electric circuit - touching a live power-line with your hand, while your feet are in contact with the ground, for instance. When you are in the train, everything metallic in the train that you can touch is joined together by the framework and chassis, so it's at the same voltage as the ground - zero volts. The 'third rail' or overhead power wire is at a dangerous voiltage, but the parts of the train that they are in contact with are insulated from the bits you can reach, so you aren't in contact with THAT, only the grounded bits of metal in the train - and there's no difference in voltage between any of the bits you can touch, so there's no shock hazard!

There's a video on YouTube of a bloke in India standing on the roof of the train carriage - earth voltage - and accidentally touching the overhead power wire - 1100 volts (I think) - and getting a fatal shock. There was a diiference in voltage between his hand and his feet..... No-one inside the train received a shock,as they were all at ground volts - so there was no differences in voltages.

Same reason birds can stand on powerlines without getting their tail-feathers blown off - both their feet are touching the same voltage wire, so there's no difference in voltage between their feet, and therefore, no shock! But if one bird stands on one power line, and pecks at another bird on a DIFFERENT power line, then there's a difference in voltages between beaks, and tail feathers fly in all directions (mainly downwards....)