Question

Internal electric connections of a multi range voltmeter are shown in the figure. The terminals are marked 3 volt, 15 volt, 150 volt, resistance of the galvanometer is $20\Omega$ and the value of current is 1 mA for the full scale deflection of the galvanometer. The resistance of $R_1$ in $k\Omega$ is-

• A. 12
• B. 15
• C. 3
• D. 2.98

Answer 1

The correct option is D 2.98

Using Ohm's law between the points having potentials 0 and 3 V,
$R_1=\frac{V}{I_g}-R_g$
$R_1=\frac{3}{I_g}-R_g=2980\Omega =2.98k\Omega$