It is possible to generate electricity from water currents. In this case, the turbine is rotated using the current , which produces mechanical energy. This turbine is coupled with generator or alternator. And this generator generates EMF based on Faraday's electromagnetic induction principle. And this generated emf is always AC voltage. In the case of AC generators, the generated EMF is supplied to the external load by means of a slip ring. And in the case of DC generators, the ACK generated with the help of commutator is converted to DC and supplied to the outside load.