Question

The essential difference between an AC generator and a DC generator is that
(A) AC generator has an electromagnet while a DC generator has permanent magnet
(B) DC generator will generate a higher voltage
(C) AC generator will generate a higher voltage
(D) AC generators has slip rings while the DC generator has a commutator

Answer 1

Hint: AC generators produce alternating current to the external circuit. DC generators maintain the direction of the current, hence a steady current to the external circuit. Split rings allow the current to flow out remaining reversed periodically. Electromagnets can be used in place of permanent magnets in any induction device.

Complete step by step answer
AC generators and DC generators are the two main types of generators that we use in generating electricity. The ac generator allows alternating current to flow into the external circuit, while dc generators allow steady one directional current to flow into the external circuit.
Both generators use the same principle known as the Faraday’s principle or law of electromagnetic induction. This can be stated as if a conductor moves in an electromagnetic field such that the flux through the area of the conductor changes, a potential difference is induced in that conductor that is directly proportional to the rate of change of the flux.
That is why in both generators, a magnet’s flux (permanent or electromagnet) is allowed to pass through a loop of coil. When the coil is rotated, the flux through the coil changes, hence it induces the desired potential. This potential difference hence can drive a current through the loop which can be connected to external circuits.
When the loop is rotated, this actually creates a current that reverses direction constantly. In the ac generator, the direction is left to reverse constantly using slip rings while dc generators used commutators to maintain the same direction.

Hence, the correct option is D.

Note
To avoid confusions, ac generators usually do generate a higher voltage than a dc generator but this cannot be considered as an essential difference. This is because the dc generator too can consciously be done to generate high voltage even though it’ll require more energy.