Question

The self induced emf of a coil is $25$ volts. When the current in it is changed at uniform rate from $10\, A$ to $25\, A$ in $1s$, the change in the energy of the inductance is :

• A. 437.5 J
• B. 637.5 J
• C. 740 J
• D. 540 J

Answer 1

Answer: (A)

437.5 J

Answer 2

$L \frac{di}{dt} =25$ $L\times\frac{15}{1} =25$ $L= \frac{5}{3}H$ $\Delta E = \frac{1}{2} \times\frac{5}{3}\times\left(25^{2} - 10^{2}\right) = \frac{5}{6} \times525 = 437.5\, J$