Answer to Question #199640 in Electrical Engineering for Manaswi

Question

A series R L circuit is connected to a 110V ac source. If the voltage across the resistor is 85 V, find the power dissipated in the circuit .

Answer 1

Since the voltages across the inductor and the resistor are $90^0$ out of phase, we obtain the voltage across the inductor in the phase domain as follows: If the voltage across the resistor is $V_1$ , the voltage across the inductor will be $jV_2$ . Assume the voltage of the source is $V_3$

Applying KVL,

$V_1+jV_2=V_1cos(\omega t)+V_2sin(\omega t)=V_3cos (\omega t-\theta^0)=85+V_2sin (\omega t)=110cos(\omega t-\theta^0)$

$110=\sqrt{85^2+V_2^2}=V_2=\sqrt{110^2-85^2}=69.82 V$