The electric train gets electricity from an overhead wire. But how does a train running underground obtain electricity? The electric train has a device called a pantograph through which it draws electricity from a live wire above the tracks. In a suburban train 3 or 4 pantographs are used to run electric motors located in various compartments.
But in many underground train systems, the current is not obtained from an overhead wire. Instead, a third rail that runs parallel to the existing two, is laid and charged with electricity. The train picks up electricity from this track. This is done to reduce the height of the tunnel. In India, the Calcutta metro railway is an example of such an arrangement. Abroad, it is used in the London Underground.
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