00:01
Here this is an rc circuit connected to a 12 volt dc battery and here the value of c is equal to 19mm.
00:13
For solving this question, remember one fact that voltage across capacitor does not change suddenly.
00:23
Means voltage across capacitor just before closing the switch that is v0 minus is equal to.
00:31
Voltage across capacitor at the instant of closing the switch is equal to voltage across the capacitor just after closing the switch that is v0 plus and also remember one more fact that if capacitor connected to a dc battery or a dc source then after a long time means when t approaches to infinity the capacitor starts to behave like and then open circuit.
01:04
T -tenths infinity means a long time after closing the switch.
01:09
Now in the circuit before closing the switch the voltage across capacitor is equal to 0 because here this capacitor does not connect to any supply before closing the switch.
01:21
And hence we can say v is 0 minus is equal to 0.
01:25
And here if v is 0 minus is equal to 0 then from this expression we can say v0 minus is equal to v0 is equal to v0 plus is equal to 0 means just after closing the switch the capacitor behaves like short circuit because voltage across this is equal to zero now from the above discussion we can say this is the circuit at t equals to 0 plus means this is the circuit just after closing the switch and in the circuit we are asked to find the current flowing through this battery and let us assume that the current flowing through this circuit at t equals to 0 plus is equal to i0 plus here in the circuit two oom and three om are connected in parallel so their parallel combination is given by 2 into 3 over 2 plus 3 and by simplifying this this becomes equal to 1 .2 om and here 4 om and 3 om are also connected in parallel so their parallel combination is equal to 4 into 3 over 4 plus 3 and by solving this this becomes equal to 1 .7 1428 om now here these two are connected in series so now by using kits off voltage low we can say i 0 plus comes equal to 12 over 1 .2 plus 1 .71 428 and by simplifying this we obtain the value of i is 0 plus is because to 4 .1176 4 mp.
03:06
So here this is the current immediately after closing the switch.
03:09
So this is the answer for part a.
03:11
Now a long time after closing this switch, this circuit looks like this because a long time after closing the switch capacitor behaves like open circuit.
03:26
And here we introduce the voltage across capacitor.
03:28
Here, air t tends to infinity.
03:32
Now suppose here current flowing through this battery, 80t tends to infinity is equal to i infinity.
03:39
Now here i ground this node...