Mains electricity is rated at 110 V110\text{ V}110 V in a particular country.
Which of the following is correct?
The mean voltage is 78 V78\text{ V}78 V.
The peak voltage is 110 V110\text{ V}110 V.
The root mean square voltage is 156 V156\text{ V}156 V.
The peak-to-peak voltage is 311 V311\text{ V}311 V.