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

Options

(a) 900Ω
(b) 1800Ω
(c) 500Ω
(d) 1000Ω

Correct Answer:

900Ω

Explanation:

Let the resistance to be added be R, then
30 = Ig (r + R)
R = 30 / Ig – r = 30 / 30 x 10⁻³ – 100
1000 – 100 = 900Ω