The switch shown in Figure 20-47 is closed and the current through the resistor

Question

The switch shown in Figure 20-47 is closed

and the current through the resistor at some instant is

6.00 A to the left. (a) What is the rate of change of the

current at that instant? (b) Is the current increasing or

decreasing? (c) What is the potential difference Va=Vb ?

(d) What would have to be true about the current for us

to deduce that it is increasing?

67. ..Calc The switch shown in Figure 20-47 is closed and the current through the resistor at some instant is 6.00 A to the left. (a) What is the rate of change of the current at that instant? (b) Is the current increasing or decreasing? (c) What is the potential difference Vb? (d) What would have to be true about the current for us to deduce that it is increasing? SSM 40 v 120 mH 8 S2

Explanation / Answer

As this is simple RL circuit, and switch is closed. So the circuit can have maximum current of value i=v/R = 40/8= 5 amp. But it is mentioned that current at some point is 6 amp. Which is not possible unless until intial condition of inductor is mentioned clearly.

Mathematically we can also check.

I(t) = V/R(1-e-Rt/L)

Which is always less than V/R = 5 amp.

So, please check the question parameters once again or ask the teacher to clarify what exactly the question is all about.

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