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To double the full scale reading of any galvanometer turned into a voltmeter, you must

$\begin {array} {1 1} (A)\;Double\: the\: resistance \: R & \quad (B)\;Half \: the \: resistance\: R \\ (C)\;Increase\: the\: resistance\: to\: 4R & \quad (D)\;None \: of \: the\: above \end {array}$

 

1 Answer

The answer requires the knowledge about the functioning of a voltmeter
and it’s construction from a galvanometer.
$V = I_G(r+ R)$
$2V = I_G(r + R’)$
$ \Rightarrow R’ = 2R + r$
Ans : (D)
answered Feb 5, 2014 by thanvigandhi_1
edited Mar 14, 2014 by thanvigandhi_1
 

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