Check your home appliances

AC voltage is sinusoidal, which has an mean value of $0$ , therefore, we cannot measure AC voltage (also AC current) by its mean value. To get a positive mean value, we square the sine curve to turn the negative half of the curve into positive before taking the mean using square root, therefore, the root-mean-square value of AC voltage. In India $V_{rms} = 220V$ , which means that the peak voltage $V_{peak} = \sqrt{2}\times 220 \approx 311V$ .

$\color{#D61F06}{\text{Previous answer: }}$ AC voltage is measured in root-mean-square value, so that we get power as $P = I_{rms}V_{rms} = I_{rms}^2 R = \dfrac{V_{rms}^2}{R}$ .

1) Average of sinusoidal value is zero;

2) Root-mean-square value is its power consumption equivalent to resistance with d.c.;

3) Peak value is 220 Sqrt (2) V;

4) One of them is the answer.