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A resistance of 980Omega is connected in...

A resistance of `980Omega` is connected in series with a voltmeter, after which the scale division becomes 50 times larger. The resistance of voltmeter is

A

`10Omega`

B

`20Omega`

C

`100Omega`

D

`200Omega`

Text Solution

Verified by Experts

The correct Answer is:
B
Let R be the resistance of voltmeter and n be the number of divisions in the voltmeter. When current `I_g` flows through voltmeter, the voltage recorded by each division of voltmeter is
`I_gR/n=V` …(i)
When resistance `980Omega` is connected in series, then
`I_g.((R+980))/(n)=50V` ...(ii)
Dividing (ii) by (i), we have
`R+980=50R`
or `R=980//49=20Omega`
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