A coil’s area is slowly increased while the magnetic field passing through it…

PHYSICS · Single correct · CBSE · Physics · Electromagnetic Induction · Electromagnetic Induction

Problem

A coil’s area is slowly increased while the magnetic field passing through it decreases in such a way that the product

BA\cos\theta

remains exactly constant in time. What is the induced emf in the coil at that instant? (a)

\displaystyle \mathcal E = B\,\dfrac{dA}{dt}

(b)

\displaystyle \mathcal E = B\,\dfrac{dA}{dt}+A\,\dfrac{dB}{dt}

(c)

0\,\text{(zero)}

(d)

\displaystyle \mathcal E = A\,\dfrac{dB}{dt}