Find the current I as a function of time for the circuit in the following figure if the switch S is closed and I=0 at t=0, where E=5 volt(s), L=2 henry(s) and R=2 ohm(s).

Question

anonymous · Answer

Is this an AC circuit or a DC circuit?.. cause if the supply is DC then inductor doesn't play a role! :-/

kropot72 · Answer

When the switch is closed the battery tries to drive a current of value E/R through the circuit, but owing to the inductance L the current is initially zero and slowly builds up to this value. It is necessary to form and solve a differential equation to find the current as a function of time. This can be found in textbooks and the solution is:
$$i=\frac{E}{R}(1-e ^{-\frac{Rt}{L}})$$

anonymous · Answer

oh this is the transient stage current right?

kropot72 · Answer

@Mashy It is better described as initial growth of current (starting from zero current due to the back emf of the inductance).

anonymous · Answer

yea.. so thats what we call as transient stage in the electronics where the current is just growing.. once it reaches a steady value, no longer will inductor contribute.. and so we call that as a steady state right? :)

kropot72 · Answer

@Mashy Yes, the steady state current is E/R.