Question

The current in a coil varies w.r.t. to time t as I = 3t² + 2t. If the inductance of coil be 10 mH, the value of induced emf at t = 2s will be

• A. 0.14 V
• B. 0.12 V
• C. 0.1 V
• D. 0.13 V

Answer 1

Answer: (A)

0.14 V

Answer 2

$e = - L \frac { d I } { d t } = - \frac { d } { d t } \left[ 3 t ^ { 2 } + 2 t \right]$ $= - L [ 6 t + 2 ] = - 10 \times 10 ^ { - 3 } [ 6 t + 2 ]$

$| e | = 0.14$ volt