A 100V voltmeter having an internal resistance of 20 kOmega is connected in series with a large resistance R across a 110 V line. What is the magnitude of resistance R if the voltmeter reads 5 V?

A 100V voltmeter having an internal resistance of 20 kOmega is connect

1.	A 100V voltmeter having an internal resistance of 20 kOmega is connected in series with a large resistance R across a 110 V line. What is the magnitude of resistance R if the voltmeter reads 5 V?
Answer» Solution : As SHOWN in fig., the voltmeter is in series with R so `V=V_(1)+V_(R)`, i.e., `110=5+V_(R)` i.e., `V_(R)=110-5=105V` And as in series POTENTIAL DIVIDES in proportion to resistance, `(V_(R))/(V_(1))=R/(R_(1)),` i.e., `105/5=R/(20kOmega)` or `R=420kOmega`

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A 100V voltmeter having an internal resistance of 20 kOmega is connected in series with a large resistance R across a 110 V line. What is the magnitude of resistance R if the voltmeter reads 5 V?

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