00:01
In this problem we have a circuit with inductor and a resistor and we have to find out the voltage across the inductor in the instant just after the switch is closed.
00:14
So resistance is r, inductance is l and the switch is closed.
00:30
Now initially the inductor has zero current through it.
00:40
So when the switch is closed the current through the inductor will remain zero because the current cannot change suddenly because that will mean infinite voltage because voltage across inductor is l -ldi upon dt.
01:04
So if the current changes suddenly the voltage across the inductor will be infinite and this cannot happen so the current in the inductor immediately after the switch is closed will be same as the current immediately before which is zero.
01:27
And since the current in the inductor is zero the current in the circuit will be zero because all the elements in circuit are in series.
01:37
So here we use the loop rule and we start from node a and we go to b then c then d.
01:51
So from loop rule we have minus vb plus potential across the resistor plus potential across the inductor equal to zero.
02:02
Now since the current is zero the potential across the resistor will be zero so the potential across the inductor is equal to the potential of the battery which is 9 .40 volts...