An alternator is responsible for recharging the car battery and delivering electricity to the car when it is still running. It consists of parts such as a rotor, stator, rectifier, housing, and shaft. The shaft is connected to the engine through a series of belts and pulleys and the rotor is fixed to the shaft. Current passes through slip rings and creates a magnetic field in the rotor. A current is induced in the stator which is converted to direct current by the rectifier. 

A failed alternator means that the vehicle cannot be restarted or recharged, leaving the driver stranded. So, if your alternator shows signs of not charging properly, make sure that you get it serviced or replaced quickly so that you do not end up stranded in the middle of the road.