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.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

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Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

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Assertion is correct but Reason is incorrect

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Both Assertion and Reason are incorrect

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Solution

The correct option is C Assertion is correct but Reason is incorrect
Efficiency of an electic motor is maximum when the back emf setup in the armature is half the value of the applied battery emf
Efficiency, $η = \frac{P_{o u t}}{P_{i n}} = \frac{e}{E} = \frac{B a c k e m f}{S u p p l y v o l a t g e}$

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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.

The correct option is C Assertion is correct but Reason is incorrectEfficiency of an electic motor is maximum when the back emf setup in the armature is half the value of the applied battery emfEfficiency, η=PoutPin=eE=Back emfSupply volatge