Assertion : An electric motor will have maximum efficiency when b… - Vidyadip

MCQ

Assertion : An electric motor will have maximum efficiency when back $emf$ becomes equal to half of applied $emf$ .

Reason : Efficiency of electric motor depends only on magnitude of back $emf$ .

A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
✓
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.

✓

Answer

Correct option: C.

If the Assertion is correct but Reason is incorrect.

c
Efficiency of an electric motor is maximum when the back $emf$ setup in the armature is half the value of the applied battery $emf$

Efficiency, $\eta \, = \,\frac{{{P_{out}}}}{{{P_{in}}}} = \frac{e}{E} = \frac{{{\text{Back emf}}}}{{{\text{Supply voltage}}}}$

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