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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.
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Solution
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 Vrms.
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