Significance of Back EMF in D.C Motor - MCQs with Answers

Significance of Back EMF in D.C Motor - MCQs with Answers

Q1. A 220 V, d.c. motor draws an armature current of 20 A. Its armature resistance is 0.6 ohm. Then the induced emf in the motor will be

a. 195 V
b. 202 V
c. 208 V
d. 215 V

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Q2. If the flux is increased by 50% and speed is reduced by 50% of a d.c. motor (keeping the other parameters constant), then its back emf will become

a. 50 % of the original back emf
b. 0.75 % of the original back emf
c. 100 % of the original back emf
d. 150 % of the original back emf

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Q3. If E_b is the back emf of d.c. motor and V is the terminal voltage, then the condition for maximum power is

a. E_b = V
b. E_b = 2V
c. E_b = ( V / 2 )
d. E_b = V ∧ 2

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