A coil of mean area 500 `cm^(2)` and having 1000 turns is held with its plane perpendicular to a uniform field of 00 . 4 G . If the coil is turned through `180^(@) ` in `(1)/(10)` second , then the average induced emf is
(Take ,1 G ` = 10^(-4) T` )

Options

A. 0 . 0 4 V
B. 0 . 4 V
C. 4 V
D. 40 V

Answer

A

Explanation

Given, , area of coil A `= 500 cm^(2) = 500 xx 10^(-4) m^(2)` number of turns N = 100, magnetic field , B = 0 . 4G ` = 0 . 4 xx 10^(-4) T`
`Delta t ` time taken ` = (1)/(10) = 0 . 1` sec , coil turned , `theta = 0 ` to
`theta 180^(@)`
Change in flux
` theta_(f) - theta_(i) = NBA cos 180^(@) - NBA cos 0^(@) = - 2NBA` We know induced emf
`E_(av) = - (Delta theta)/(Delta t) = (2NBA)/(Delta t) = (2 xx 1000 xx 0 . 4 xx 10^(-4) xx 0 . 05)/( 0 . 1)`
0 . 0 4 V