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

Options

A. input voltage cannot be AC voltage, but a DC voltage
B. maximum input voltage is 220V.
C. the meter reads not v but `lt v^(2) gt` and is calibrated to read `sqrt(lt v^(2) gt)`
D. the pointer of the meter is stuck by some mechanical defect.

Answer

C

Explanation

The voltmeter connected to AC mains reads mean value `(lt v^(2) gt)` and is calibrated in such a way that it gives value of `lt v^(2)gt`, which is multiplied by form factor to give rms value.