I just need answer for question 4 and i already have answers for 1,2,3 which are

Question

I just need answer for question 4 and i already have answers for 1,2,3 which are correct can you please tell me whats the answer for number 4

A circuit is constructed with four resistors, one inductor, one battery and a switch as shown. The values for the resistors are: R1 = R2 = 29 , R3 = 74 and R4 = 100 . The inductance is L = 350 mH and the battery voltage is V = 12 V. The positive terminal of the battery is indicated with a + sign.

1)

The switch has been open for a long time when at time t = 0, the switch is closed. What is I4(0), the magnitude of the current through the resistor R4 just after the switch is closed?

0.05911 A

2)

What is I4(), the magnitude of the current through the resistor R4 after the switch has been closed for a very long time?

0.08009 A

3)

What is IL(), the magnitude of the current through the inductor after the switch has been closed for a very long time?

0.05754 A

4)

After the switch has been closed for a very long time, it is then opened. What is I3(topen), the current through the resistor R3 at a time topen = 8.8 ms after the switch was opened? The positive direction for the current is indicated in the figure.

______A

Explanation / Answer

4) just before switch was closed,

IL = 0.05754 A

current in inductor does not change instantly.

I3 = - IL = - 0.05743 A .........Ans

after that,

time constant, T = L / (R2 + R3) = 3.398 x 10^-3 s

I = IL [e^(-t/T)]

I = - 0.05743 [e^(-8.8/3.398)]

I = 4.31 x 10^-3 A .......Ans

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