Question

A series RC circuit has R = 15 Ω and C = 1 μF. The current in the circuit is 5 sin 10t. The applied voltage is _____________

(a) 218200 cos (10t – 89.99°)

(b) 218200 sin (10t – 89.99°)

(c) 218200 sin (10t)

(d) 218200 cos (10t)

This question was addressed to me in an interview for job.

I'm obligated to ask this question of Advanced Problems on Application of Laplace Transform in portion Application of the Laplace Transform in Circuit Analysis of Network Theory

Answer 1

The correct answer is (b) 218200 sin (10t – 89.99°)

For explanation: Given that, R = 15Ω, XC = \(\frac{1}{ωC}\)

= \(\frac{10^6}{10 X 1}\) = 10^5  Ω

Now, θ = tan^-1 \(\frac{X_C}{R}\) = 89.99°

We know that, impedance Z is given by,

Z = \(\sqrt{R^2 + X_C^2}\) = 10^2 kΩ.

Hence, V = 100000(2.182).sin(10 t – 89.99°)

Or, V = 218200 sin (10t – 89.99°).