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# A galvanometer with a coil resistance $12 \Omega$ shows a full scale deflection for a current $2.5\;mA$ How will you convert it into a voltmeter of range $7.5 \;V$ Also find the total resistance of Voltmeter formed ?

$\begin{array}{1 1} 3\;\Omega \\ 0.003\;\Omega \\ 300\;\Omega \\ 3000 \;\Omega \end{array}$

$R= \large\frac{v}{I_g}$$-a=\large\frac{7.5}{2.5 \times 10^{-3}}$$-12$
$\qquad= 2988\;\Omega$
Total resistance of voltmeter $=R+G$
$\qquad= 2988+12$
$\qquad= 3000\;\Omega$
Answer : $3000 \;\Omega$