Question

Which device uses slip rings?
A. A d.c electric motor
B. A relay
C. A transformer
D. An a.c generator

Answer 1

Hint: Slip ring is a device that is used to transmit the power and electrical signal from a stator to a rotor. It improves the mechanical performance of the device. To answer this question, check which device mentioned in the options has a rotor and stator so that the slip rings are fitted to the rotor.

Complete step by step answer:
As we know, a slip ring is a device that is used to transmit the power and electrical signal from a stator to a rotor. Thus, we can say the slip ring is used in a device which requires the transmission of power to the rotating structure. It improves the mechanical performance of the device and also eliminates the chance of breaking the wiring structure from the movable joints.Now, to answer this question, let us see which device has a rotor and stator so that the slip rings are fitted to the rotor.

In a d.c electric motor, the commutators are used instead of slip rings. The commutators are similar to the slip rings but have critical distinctions. In the d.c motors, commutators are used to reverse the polarity of current in the armature coils. Therefore, the option A is incorrect.

We know that a relay and a transformer are not the devices which have rotors and stators. These are stationary structures and don’t need the use of slip rings. Therefore, option B and C are incorrect.

In an a.c generator, the slip rings are fitted to the rotor which improves its performance. The slip rings provide a resistance to the rotor wirings. Recently, the modified slip rings are able to transmit analog and digital signals in devices such as temperature sensors.

So, the correct answer is option D.

Note:Though slip rings sound familiar to commutators, they cannot be used in the d.c motors to transmit power. Slip rings are used only in the structure which has both stator and rotor. The slip rings are used along with the carbon brushes so that the ends of the coils are connected to the external circuit.