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Physics - Current Electricity Question with Solution | TestHub

PhysicsCurrent ElectricityElectrical instrumentMedium3 minQB

PhysicsMediumsingle choice

A D.C. supply of $120$ V is connected to a large resistance $X$ . A voltmeter of resistance $10 kΩ$ placed in series in the circuit reads $4$ V. This is an unusual use of a voltmeter for measuring very high resistance. The value of $X$ is:

Options:

Answer:

Solution:

$I = \frac{4}{10 \times 1 0 ^{3}} = 4 \times 1 0^{- 4}$ A
$4 \times 1 0^{- 4} = \frac{120}{X + 1 0 ^{4}}$
$4 \times 1 0^{- 4} X + 4 = 120$
$X = \frac{116}{4} \times 1 0^{4} = 290 kΩ$

Subject:PhysicsTopic:Current ElectricitySubtopic:Electrical instrument

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