Question

A ring of radius r is rotating about its diameter with angular velocity ω in a perpendicular magnetic field vector B It has 20 turns. The emf induced is

(a) 20Bπr² sin wt 

(b) 20Bπr² cos wt 

(c) 10√2Bπr² 

(d) 20Bπr²w sin wt

Answer 1

The correct option (d) 20Bπr²w sin wt 

Explanation:

e   = – N(dɸ/dt)

= – N (d/dt) (AB cos wt)

= – NAB (– 1) sinwt × w

= NABw sin wt

Here N = 20, A = πr²

∴ e = 20Bπr²w sin wt.