Magnetic flux linked with one coil changes with time t is `phi=xt^2` . If emf induced at t=3s is 9 V then value of x = ......

Options

A. 0.66 `"Wb s"^(-2)`
B. 1.5 `"Wb s"^(-2)`
C. `-0.66 "Wb s"^(-2)`
D. `-1.5 "Wb s"^(-2)`

Answer

D

Explanation

`phi=xt^2`
`therefore (dphi)/(dt)=2xt`
Induced emf,
`epsilon=-(dphi)/(dt)`
`epsilon=-2xt`
`therefore x=-epsilon/(2t)=-9/(2xx3)=-1.5 "Wb s"^(-2)`