Name a common source of power for electric trains.

Electric trains commonly draw their power from overhead catenary lines or third rail systems. This technology is fundamental to their operation. Overhead catenary systems feature wires suspended above the train that supply electric power through a pantograph attached to the train roof. This method provides a consistent and reliable source of electricity, allowing electric trains to travel long distances without needing to stop for fuel.

Third rail systems, on the other hand, have an additional rail that runs alongside the conventional tracks, supplying power directly to the train through a pickup shoe or contactor. This system is often seen in subway systems and some rail networks.

Both catenary and third rail systems are efficient means of transmitting electricity, making them the primary choices for electric train infrastructure. Other options such as diesel generators, geothermal energy, or natural gas turbines do not typically constitute the main power source for electric trains, as these alternatives involve different mechanisms or technologies primarily used in other contexts.