Question

The magnetic flux linked with a coil is $\varphi$ and the emf induced in it is e

• A. $If\varphi =0,$ e must be zero
• B. $If\varphi \ne 0$ , e cannot be zero
• C. If e is not 0,$\varphi$ may or may not be 0
• D. None of the above is correct

Answer 1

The correct option is C If e is not 0,$\varphi$ may or may not be 0

Emf $\epsilon =-N\frac{d\varphi }{dt}$

Where, $\varphi =$ flux and $\frac{d\varphi }{dt}$ is the rate of flux change.

It is clear from above that emf doesn’t depend on flux, it is depend on rate of flux change.

Example : $\varphi =B.A\cos \varphi$ and $\frac{d\varphi }{dt}=-B.A\sin \varphi$

At ${90}^o$ angle in above example flux is zero but rate of flux change is maximum.

Hence, even if $\varphi$ is zero, emf can or cannot be zero.