1.

The figure below shows a circuit for an AC voltmeter. It utilizes a moving-coil meter that gives a full-scale reading when the average current flowing through it is 1 mA. The moving-coil meter has a 50-Ω resistance. The value of R that results in the meter indicating a full-scale reading when the input sine-wave voltage VI is 20 V peak-to-peak is(a) 3.183 kΩ(b) 3.133 kΩ(c) 3.183 Ω(d) 56.183 ΩThe question was asked in an online interview.This key question is from The Ideal Diode in portion Diodes of Electronic Devices & Circuits

Answer»

Right option is (b) 3.133 kΩ

To explain I WOULD say: Average value of input VOLTAGE= 20/π or 6.366 V.

Since there is diode half of the time there is no voltage across the voltmeter hence the average value of the input voltage is 10/π or 3.183V.

The total resistance required to generate 1MA current is 3.183 kΩ out of which 50Ω is PROVIDED by the moving COIL. Therefore, a resistance of 3.133 kΩ is required.



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