Question

When a current of $5mA$ is passed through a galvanometer having a coil of resistance $15\Omega$, it shows full scale deflection. The value of the resistance to be put in series with the galvanometer to convert it into a voltmeter of range $0-10V$ is:

• A. $4.005\times {10}^3\Omega$
• B. $1.985\times {10}^3\Omega$
• C. $2.045\times {10}^3\Omega$
• D. $2.535\times {10}^3\Omega$

Answer 1

Answer: (B)

$1.985\times {10}^3\Omega$

$V=ig(R_3+R_4)$

$10=(5\times {10}^{-3})(15+R_5)$

$15+R_5=\frac{10}{5\times {10}^{-3}}=2\times {10}^3$

$R_5=2000-15\Omega$

$R_5=1985\Omega$

$R_5=1.985k\Omega$

Option (2) is correct.