Question

A rectangular coil $ABCD$ is rotated anticlockwise with a uniform angular velocity about the axis shown in the Fig. The axis of rotation of the coil as well as the magnetic field $B$ are horizotally. The induced emf in the coil would be minimum when the plane of the coil would be

• A. is horizotal
• B. makes an angle of ${45}^o$ with the direaction of magnetic field
• C. is at right angle to the magnitude field
• D. makes an angle of ${30}^o$ with the magnitic field.

Answer 1

The correct option is C is at right angle to the magnitude field

Magnetic flux in the coil when held in the magnetic field is given by :

$\varphi =BA\sin \omega t$

So $E=\frac{-d\varphi }{dt}$

$E=-BA\cos \omega t$

So induced emf will be minimum when $\omega t={90}^0$

So, the induced emf in the coil would be minimum when the plane of the coil is at right angle to the magnitude field.