A) half
B) two times
C) four times
D) unchanged.
Correct Answer: B
Solution :
If A is the area of the coil, there are N turns in the coil, \[\omega \] being the angular velocity of the armature, then the flux through each turn in time t is given by \[\phi =BA\cos \omega t\] Using Faradays Law, the emf induced in each turn of the coil is \[-\frac{d\phi }{dt}=BA\omega \sin \omega t\] The total induced emf in the coil \[\varepsilon =NBA\omega \,\,\sin \omega t\] Now if we double \[\omega ,\,\,\varepsilon \] will be doubled.
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