Question

A rectangular, square, circle and elliptical loop, all in $xy-$ plane, are moving out of a uniform magnetic field with a constant velocity $V=v\hat{i}$. The magnetic field is directed along negative $z-$ axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for

• A. any of the four loops
• B. the rectangular, circular & elliptical loops.
• C. the circular and elliptical loops
• D. only the elliptical loop

Answer 1

The correct option is C the circular and elliptical loops

According to the Faraday's law of electromagnetic induction & Lenz's law, the emf induced in the loop is,

$E_{induced}=\frac{-d\varphi }{dt}$

Where, $\varphi =NBA$

Here, area is variable.

$\therefore E_{induced}=-NB\frac{dA}{dt}$


Out of the four figures when the circular and elliptical loops come out from the field, equal area is not traced in equal interval of time.

So induced emf in both circular and elliptical loops is not constant.

Hence, $\left(C\right)$ is the correct answer.