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 horizontally.the induced emf in the coilwould be minimum when the plane of the coil

A. (a) is horizontal
B. (b) makes an angle of `45^(@)` with the direction of magnetic field
C. ( c) is at right angle to the magnetic field
D. (d) makes an angle of `30^(@)` with the magnetic field

Answer 1

Correct Answer - C
(c ) Let `theta` is the angle between area vector of coil and magnetic field. Then flux through coil: `phi = BA cos theta`

Induced emf: `e = - (dphi)/(dt) = BA sin theta ((d theta)/(dt))`
`rarr` `e = Baomega win theta`
`e` is minimum, when `theta = 0^(@)`, or when plane of coil is at right angle to magnetic field.