A coil of area `500cm^(2)` and having `1000` turns is held perpendicular to a uniform field of `0.4` gauss. The coil is turned through `180^(@)` in `1//10sec` . Calculate the average induced e.m.f.

Options

A. 0.02 V
B. 0.04 V
C. 1.4 V
D. 0.08 V

Answer

B

Explanation

Here, `A=500cm^(2)=500xx10^(-4)m^(2)`
`N=1000,B=0.4G=0.4xx10^(-4)T`
`t=(1)/(10)s`
When the coil is held perpendicular to the field, the normal to the plane of the coil makes an angle of `0^(@)` with the field B.
`:.` initial flux, `phi_(1)=BAcos0^(@)=BA`
final flux, `phi_(2)=BAcos180^(@)=-BA`
Average induced emf,
`epsi=-N((phi_(2)-phi_(1))/(t))=-N((-BA-BA)/(t))`
`=(2NBA)/(t)=(2xx1000xx0.4xx10^(-4)xx500xx10^(-4))/(1//10)=0.04V`