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Conversion of Galvanometer to Voltmeter |
A galvanometer can be converted into voltmeter of given range by connecting a suitable resistance \[{{R}_{s}}\] in series with the galvanometer, whose value is given by |
\[{{R}_{s}}=\frac{V}{{{I}_{g}}}-G\] |
where V is the voltage to be measured, \[{{I}_{g}}\] is the current for full scale deflection of galvanometer and G is the resistance of galvanometer. |
Series resistor \[\left( {{R}_{s}} \right)\]increases range of voltmeter and the effective resistane of galvanometer. It also protects the galvanometer from damage due to large current. |
Voltmeter is a high resistance instrument and it is always connected in parallel with the circuit element across which potential difference is to be measured. An ideal voltmeter has infinite resistance. |
In order to increase the range of voltmeter n times the value of resistance to be connected in series with galvanometer is \[{{R}_{s}}=\left( n-1 \right)G\]. |
A) \[0\centerdot 975\Omega \]
B) \[99\centerdot 75\Omega \]
C) \[975\Omega \]
D) \[99\,75\,\Omega \]
Correct Answer: D
Solution :
A galvanometer can be converted into a voltmeter of given range by connecting a suitable high resistance R in series of galvanometer, which is given by \[R=\frac{V}{{{I}_{g}}}-G=\frac{100}{10\times {{10}^{-3}}}-25=10000-25\] \[=9975\,\,\Omega \].You need to login to perform this action.
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