An e.m.f. `E=4cos(1000t)`volt is applied to an `LR` circuit of inductance `3mH` and resistance `4ohm`. The amplitude of current in the circuit is

Options

A. 8A
B. 4A
C. 0.8A
D. 0.4A

Answer

C

Explanation

Here , `V_0 = 4V, omega = 1000 , L = 3 mH = 3 xx 10^(-3) H, R = 4Omega `
The inductive reactance is
`X_L = omega L = 1000 xx 3 xx 10^(-3) Omega = 3 Omega `
The impedance of the circuit is
`Z = sqrt(R^2 + X_L^2) = sqrt((4)^2 + (3)^2) = 5Omega `
`I_0 = (V_0)/(Z) = 4/5 = 0.8A`