need to find the induced e.m.f. and stored energy at the end of the time?

Question

the question:

the current in a 3.5H(henry) inducator increses uniformly from zero to 50 mA in 500 ms.
determine the e.m.f.,and the stored energy at the end of this time?

help i have no clue =| and thats all ive been given
cheers

Answer 1

Entered 'unductance basic theory' in the search box below and choose the first hit. One of the formulii it give are: E = -L di/dt, where L is, I think, inductance.

So, assuming this is the formula you are after, not much evidence for this but suspect it is, then di/dt = (0 - 50/1000)/500/1000 = -1000.0001 is this right?

Hence emf, E = same * 3.5 = 3500 volts.

Same source; magnetic energy stored is 0.5*Li**2. 0.21875 (Joules presumably). If this works for God's sake make me the best answer.

Answer 2

Rate of change of current dI/dt = E/L (I=current, E=voltage, L=inductance).
Energy = LI^2/2.
An inductance behaves similarly to a capacitance with the roles of E and I interchanged. See the refs.