Question

When a voltage measuring device is connected to AC mains, the meter shows the steady input voltage of 220V. This means ______.

Options

• input voltage cannot be AC voltage, but a DC voltage.

• maximum input voltage is 220 V.

• the meter reads not v but <v²> and is calibrated to read `sqrt(< v^2 >)`.

• the pointer of the meter is stuck by some mechanical defect.

Answer 1

When a voltage measuring device is connected to AC mains, the meter shows the steady input voltage of 220V. This means the meter reads not v but <v²> and is calibrated to read `underline(sqrt(< v^2 >))`.

Explanation:

The voltmeter in AC circuit reads value [< v² >] and meter is calibrated to r.m.s. value < v² > which is multiplied by `sqrt(2)` to get V_rms.