Question

In an AC circuit, resistance 50 Ω, inductance 0.3 H and capacitance 15 μF is connected to an AC voltage source 25 V, 50 Hz. Determine the current in the circuit.

(a) 0.01 A

(b) 0.2 A

(c) 0.02 A

(d) 0.002 A

The question was asked during an interview.

The above asked question is from Kirchhoff’s Laws and Network Solution topic in chapter Network Theorems Applied to AC Networks of Basic Electrical Engineering

Answer 1

The correct answer is (b) 0.2 A

Explanation: Z^2 = R^2+(XL-XC)^2, XL=2πfL,  XC=1/(2πfC)    f=50Hz and L=0.3H and C=15 μF

XL=2π(50)(0.3)= 94.25 ohm .

XC=1/(2π*50*15*10^-6) =  212.21 ohm.

Z^2=50^2+(212.21-94.25)^2=15625

Z = 125 ohm.

Current in the circuit i=V/Z=25/125=0.2 A.