Question

A galvanometer of resistance $50\Omega$ gives full scale deflection with a current of $0.5mA$. The value of resistance to be connected in series with it, in order to convert it into a voltmeter of range 10 volt, will be

• A. $1,995\Omega$
• B. $2,000\Omega$
• C. $19,950\Omega$
• D. $20,000\Omega$

Answer 1

The correct option is C $19,950\Omega$

Now , galvanometer resistance is $50\Omega$
and full scale deflection current is $0.5mA$
Now we have to convert it into a voltmeter of range $10V$
therefore, resistance of galvanometer is to be made,
$R=\frac{V}{I_{fullscale}}=\frac{10}{0.5\times {10}^{-3}}=20000\Omega$
therefore, additional resistance in series required is $R_s=R-R_{galvo}$
$R_s=20000-50=19950\Omega$
option(C)