An AC voltage source, with a peak output of 72 V, results in dissipation of energy in a resistor at rate of 140 W. What is the value of the resistance?

18.51 Ω

Explanation:

Power dissipated in electric circuits is given by P = IV

But, V = IR And I = V/R

P = (V/R) V = V²/R

But this is an AC circuit, and the voltage in the power dissipated equation is the DC voltage.

DC voltage of the AC circuit = Vrms = (Vpeak)/√2 = 72/√2 = 50.912 V

P = V²/R

R = V²/P = 50.912²/140 = 18.51 Ω

increases it