## guddosyal 2 years ago 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).

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1. Mashy

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

2. kropot72

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: $i=\frac{E}{R}(1-e ^{-\frac{Rt}{L}})$

3. Mashy

oh this is the transient stage current right?

4. kropot72

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

5. Mashy

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? :)

6. kropot72

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