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Objective Questions:

1. Direction of rotation of a coil in electric motor is determined by
(a) fleming’s right hand rule
(b) fleming’s left hand rule
(c) faraday law of electromagnetic inductors
(d) None of above
2. In electric motor, to make the coil rotating continuously in the same direction,
current is reversed in the coil after every half rotation by a device called
(a) carbon brush
(b) commutator
(c) slip ring
(d) armature
3. Commercial electric motors do not use
(a) an electromagnet to rotate the armature
(b) effectively large number of turns of conducting wire in the current carrying coil
(c) a permanent magnet to rotate the armature
(d) a soft iron core on which the coil is wound
4. A __________ works on the principle that when a rectangular coil is placed in a
magnetic field and current is passed through it, a force acts on the coil which
rotates it continuously.
5. The direction of magnetic force acting on a charged particle moving in a
magnetic field can be found by ……….. .
6. According to Fleming’s left hand rule, if the first finger points in the direction of
……….., the second finger
in the direction of ……….., then the thumb will point in the direction of ……….. .

Subjective Questions:

1. What does a commutator do in an electric motor?

2. What appliances use electric motors?

3. Why do electric motors have brushes?

4. What are the advantages of DC motors?

5. What's the difference between AC and DC motors?