Question Detail
Question
An inductor, L = 0.5H, in series with a resistor, R = 250Ω, are connected to an a.c. source 100v, 50Hz. Determine the apparent power of the circuit.
Correct Answer
Option A is the correct answer.
Detailed Explanation
Apparent power (S) in an AC circuit is given by S = Vrms × Irms. First, calculate the impedance (Z) of the series RL circuit.Given:Inductance L = 0.5 HResistance R = 250 ΩRMS voltage Vrms = 100 VFrequency f = 50 HzCalculate the angular frequency ω = 2πf:ω = 2π × 50 Hz = 100π rad/sCalculate the inductive reactance XL = ωL:XL = 100π rad/s × 0.5 H = 50π Ω ≈ 157.08 ΩCalculate the impedance Z = √(R2 + XL2):Z = √(2502 + (50π)2)Z = √(62500 + 24674.01) = √87174.01 ≈ 295.25 ΩCalculate the RMS current Irms = Vrms / Z:Irms = 100 V / 295.25 Ω ≈ 0.3387 ACalculate the apparent power S = Vrms × Irms:S = 100 V × 0.3387 A = 33.87 VARounding to one decimal place, the apparent power is 33.9 VA.
Hint
Apparent power is the product of RMS voltage and RMS current. First, find the inductive reactance, then the total impedance of the circuit, and finally the RMS current.