A rectangular, a square , a circular and an elliptical loop, all in the `(x-y)` plane, are moving out of a uniform magnetic field with a constant velocity `vec(v)=vhati` . The magnetic field is directed along the negative `z`-axis direction. The induced emf, during the passage of these loops , out of the field region, will not remain constant for :

Options

A. The rectangular, circular and elliptical loops
B. The circular and the elliptical loops
C. Only the elliptical loop
D. Any of the four loops

Answer

B

Explanation

`e=(dvarphi)/dt=B(dA)/dt`
As `(dA)/dt` = constant for rectangular and square loop
`(dA)/dtne` constant for circular and elliptical loop.