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

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

and it’s construction from a galvanometer.
$V = I_G(r+ R)$
$2V = I_G(r + R’)$
$\Rightarrow R’ = 2R + r$
Ans : (D)
edited Mar 14, 2014