A coil has 1,000 turns `500 cm^(2)` as its area.The plane of the coil is placed at right angles in a magnetic induction field of `2xx10^(-5)Wbm^(-2)`.The coil is roatated through `180^(@)`in 0.2 s'.The average emf induced in the coil, in mV is

Options

A. 5
B. 15
C. 10
D. 20

Answer

B

Explanation

Average e.m.f induced =`(dphi)/(dt)`
`(phi_(1)-phi_(2))/(dt)=(NBAcos0_(1)-NBAcos02)/dt`
`=NBA(cos0^(@)cos180^(@))/dt=(NBA(2))/dt`
` = (2xx1000xx2xx10^(-5)xx5xx10^(-2))/(0.2)=1xx10^(5)xx10^(-5)xx10^(-2)`
` =10^(-2)V or 10mV.`