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(B) According to Faraday's law of electromagnetic induction,the induced $e.m.f.$ $(e)$ is given by $e = -\frac{d\phi}{dt}$,where $\phi$ is the magneti

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Lines of force are maximum but induced $e.m.f.$ is zero.

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(B) According to Faraday's law of electromagnetic induction,the induced $e.m.f.$ $(e)$ is given by $e = -\frac{d\phi}{dt}$,where $\phi$ is the magnetic flux (number of magnetic lines of force).When the coil is rotating,the magnetic flux $\phi$ varies as $\phi = BA \cos(\omega t)$.The induced $e.m.f.$ is $e = -\frac{d}{dt}(BA \cos(\omega t)) = BA\omega \sin(\omega t)$.When the number of magnetic lines of force is maximum,$\phi$ is maximum,which occurs when $\cos(\omega t) = 1$ (i.e.,$\omega t = 0$ or $\pi$).At these positions,$\sin(\omega t) = 0$,so the induced $e.m.f.$ $(e)$ becomes zero.Therefore,when the lines of force are maximum,the induced $e.m.f.$ is zero.

The coil of a dynamo is rotating in a magnetic field. The developed induced $e.m.f.$ changes and the number of magnetic lines of force also changes. Which of the following conditions is correct?

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