Question

A coil with a self-inductance of 4 H and a resistance of 10 is connected across a 25 V battery of negligible internal resistance.

(a) What is the final current?

____________A

(b) How much energy is stored in the inductor when the final current is attained?

____________J

Answer 1

This is a RL circuit connencted to a DC voltage V = 25 V.
The equation for the total voltage is
   






Now, at t = 0, I(0) = 0. So, we get
  

And so
  


a)

The final current is calculated when the time t goes to infinity. And the final current is
   


b)

  The energy stored in the inductor is
  


So, for the final current energy stored in the inductor is