1.

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

Answer»

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

Solution :AC voltmeter reads the rms value of voltage,
`therefore V_"rms"=V_m/sqrt2`
The voltmeter connected to AC mains read MEAN value `ltV^2gt` (AVERAGE value) and is calibrated in such a way that it GIVES value of `ltV^2gt`. This is obtained by dividing `sqrt2` to maximum voltage `V_m`.


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