A third rail is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. Third rail systems are always supplied from direct current electricity.
Correspondingly, what does it mean to touch the third rail?
A third rail is an issue that politicians and officials don't want to touch because it's too controversial. The idiom refers to the actual third rail used in electric rail systems. The third rail carries a high voltage, so touching it is extremely dangerous. Third rail is originally American.
What is the voltage of the third rail?
A range of voltages has been used, employing both overhead lines and conductor rails; the two most common systems are 25 kV AC using overhead lines and the 750 V DC third rail system used in southeast England and on Merseyrail.
What is a third rail slang?
The third rail of a nation's politics is a metaphor for any issue so controversial that it is "charged" and "untouchable" to the extent that any politician or public official who dares to broach the subject will invariably suffer politically. It is most commonly used in North America.