A planar loop of wire rotates in a uniform magnetic field. Initially at t =0, the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of 10 s about an axis in its plane, then the magnitude of induced emf will be maximum and minimum, respectively at

Options

A. 2.5 s, 5 s
B. 5s , 7.5 s
C. 2.5 s , 7.5 s
D. 10s, 5s

Answer

A

Explanation

`rArr omega=(2pi)/T =(2pi)/10`
`therefore omega=pi/5`….(1)
when `omegat=pi/2`, then flux associated with ring is minimum and induced emf is maximum.
`therefore t=(pi//2)/omega = (pi//2)/(pi//s)=5/2`=2.5 s (From equ. (1))
and when `omegat=pi` then flux associated with ring is maximum and induced emf is minimum .
`therefore t=pi/omega`
`=pi/(pi//5)` (`because` From equation (1))
t=5s
`therefore` (2.5 s, 5s)