Shown below is a LR circuit with a battery and a switch S . L is the inductance

Question

Shown below is a LR circuit with a battery and a switch S. L is the inductance of the inductor, and V is the voltage across the battery.

The switch is left open for a long time. At time t = 0 the switch is closed and the current flowing through the circuit is measured as a function of the time.

If the value of the resistor in the circuit is R = 17.4 , the largest current measured is Imax = 0.97 A, and the time constant (the time to reach about 63% of the maximum current) is found to be = 11.7 ms,

(a) what is the voltage V across the battery?
_____ Volt

(b) What is the value of the inductance L of the inductor in the circuit?
_____ mH (mili-Henry)

Explanation / Answer

a) Imax*R = 0.97*17.4 = 16.87 V

b) time constant =L/R
11.7*10^-3 = L/17.4

L= 0.20 H= 200 mH

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