A time varying magnetic flux passing through a coil is given by `phi=xt^(2)`, if at `t=3s`, the emf induced is 9 V, then the value of x is

Options

A. `0.66 Wbs^(-2)`
B. `1.5 Wbs^(-2)`
C. `-0.66 Wbs^(-2)`
D. `-1.5 Wbs^(-2)`

Answer

D

Explanation

Given `phi = xt^2 , , therefore (dphi)/(dt) = 2xt`
Induced emf , `epsi = - (dphi)/(dt) = -2xt , therefore x = -(epsi)/(2t)`
At ` t = 3s, x =- (9)/(2 xx 3) = -1.5 Wb s^(-2)`