Question

What is the power in the magnetic field if the current in a coil has a constant inductance of L henrys grows at a uniform rate?

(a) LI/2t

(b) LI^2/2t

(c) L/2It

(d) L/2I^2t

This question was posed to me at a job interview.

Question is taken from Energy Stored in an Inductor topic in section Inductance in a DC Circuit of Basic Electrical Engineering

Answer 1

Right option is (b) LI^2/2t

For explanation I would say: EMF induced in the coil is Ldi/dt.

Energy=ei*dt=Lidi/dt*dt=Li^2/2.

Power=Energy/Time = Li^2/2t.