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A D.C. supply of 120 V is connected to a...

A D.C. supply of 120 V is connected to a large resistance X. A voltmeter of resistance `10kOmega` placed in series in the circuit reads 20 V. This is an unusual use of voltmeter for measuring very high resistance. The value of X is ……… `x+10kOmega` (approx).

Text Solution

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`I=(20)/(10xx10^(3))=20xx10^(-4)`
But `20xx10^(-4)=(120)/(x+10^(4))` or `20xx10^(-4)x+20=120`
`therefore x =((120-20)/(20))xx10^(4)`
`=5xx10^(4) Omega`
`=50 k Omega`
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