The current `i` in a coil varies with time as shown in the figure. The variation of induced emf with time would be

Options

A.
B.
C.
D.

Answer

A

Explanation

Induced emf, `e = - L (di)/(dt)`

e will depend on `(di)/(dt)`
If slope of graph `((di)/(dt))` is +ve , e will be negative.
For `0 le t le T/4`
`(di)/(dt)` = constnat and +ve, So e = -ve and constant
For `T/4 le t le T/2 (di//dt = 0 , e = 0)`
For `T/2 le t le (3T)/4`
`(di)/(dt) ` = Constant and -ve, so, e = +ve and constant
Hence , graph of e - t is :