Question

The LR circuit has a resistor R = 20 Ohms and an inductor L = 20 mH. hen switch closes, the circuit is connected to a battery that provides a dc voltage of 20V. What is the current through the battery 2 ms after the switch closes?

Answer 1

Given,

The resistance of the resistor, R=20 Ω

The inductance of the inductor, L=20 mH

The battery voltage, V=20 V

The time instant, t=2 ms=2×10⁻³ s

The instantaneous current through an LR circuit is given by,

`I=(V)/(R)(1-e^{(-Rt)/(L)})`

On substituting the known values,

`\begin{gathered} I=(20)/(20)(1-e^{(20*2*10-3)/(20*10-3)}) \\ =6.39\text{ A} \end{gathered}`

Thus the instantaneous current through the circuit is 6.39 A