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A resistance of 1980Omega is connected i...

A resistance of `1980Omega` is connected in series with a voltmeter, after which the scale division becomes 100 times larger. Find the resistance of voltmeter.

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Let R be the resistance of voltmeter. Let n be the number of divisions in the voltmeter. The voltage `(V)` recorded by each division of voltmeter when current `i_g` flows through it is
`i_gR//n=V` …(i)
When resistance is connected in series with voltmeter, then
`i_g(R+1980)//n=100V` ...(ii)
Dividing (ii) by (i), we get
`R+1980=100R` or `R=1980//99`
`=20Omega`
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