Magnetic flux `phi` (in weber) linked with a closed circuit of resistance `10 ohm` varies with time `t` (in seconds) as
`phi=5t^(2)-4t+1`
The induced electromotive force in the circuit at `t=0.2` sec. is

Options

A. 0.4 volts
B. `-0.4` volts
C. `-2.0` volts
D. `2.0 ` volts

Answer

D

Explanation

`phi = 5t^2 - 4 t + 1`
`(d phi)/(dt) = 10 t - 4`
`= 10 xx 0.2 - 4 = 2 - 4 = -2 "volt"`
`V = - (d phi)/(dt) = -(-2) = +2` volt.