A 80Ω resistor is connected to a 240 V, 50 Hz ac supply. The net power consumed over a full cycle is

720 W

The correct answer is Option (4) → 720 W

For a pure resistor in AC circuit, the net power over a full cycle is given by:

$P = V_\text{rms}^2 / R$

Given: $R = 80\ \Omega$, $V_\text{rms} = 240\ \text{V}$

Substitute values:

$P = \frac{(240)^2}{80} = \frac{57600}{80} = 720\ \text{W}$

Final Answer: $P = 720\ \text{W}$