A 800 turn coil of effective area `0.05 m^(2)` is kept perpendicular to a magnetic field `5xx10^(-5)` T. When the plane of the coil is rotated by `90^(@)` around any of its coplanar axis in 0.1 s, the emf induced in the coil will be:

Options

A. 0.02 V
B. 2V
C. 0.2 V
D. `2 xx 10^(-3)` V

Answer

A

Explanation

Initially coil is placed perpendicular to magnetic field, so aren vector is parallel to magnetic field, hence magnetic flux linked with the coil is zero.
`phi_(1)= 0`
In second when coil turn through an angle `90^(@)` then angle between area vector and magnetic field becomes `90^(@)`. Magnetic flux can be written as follows: `phi_(2) = NBA sin theta = 800 xx 5 xx 10^(-5) xx 0.05 xx sin 90^(@) = 2 x 10^(-3)`
Induced emf can be written as follows:
`emf= |(Deltaphi)/(Deltat)|= (2 xx 10^(-3))/(0.1)= 0.02V`
Hence option (a) is correct.