Question

A galvanometer has coil of resistance 100 ohm and gives a full scale deflection for 30 mA current. If it is to work as a voltmeter of 30 volt range, the resistance required to be added will be :

• A. $1000\Omega$
• B. $900\Omega$
• C. $1800\Omega$
• D. $500\Omega$

Answer 1

Answer: (B)

$900\Omega$

Let required resistance be R then

$(R+R_g)I_g=V\Rightarrow (R+100)(30\times {10}^3)=30$

$\Rightarrow R=900\Omega$