Question

A galvanometer of resistance 20 Ω has a current sensitivity of 5 div/mA. The instrument has 50 divisions. It can be converted into a voltmeter reading up to 25 volts by connecting a resistance of ______

Options

• 2480 Ω in series

• 20 Ω in parallel

• 1240 Ω in series.

• 2480 Ω in parallel

Answer 1

A galvanometer of resistance 20 Ω has a current sensitivity of 5 div/mA. The instrument has 50 divisions. It can be converted into a voltmeter reading up to 25 volts by connecting a resistance of 2480 Ω in series.

Explanation:

Current sensitivity = 5 div/mA

∴ for 50 div, the current l_g = 10 mA = 10^-2 A

G = 20 Ω

`R = V/I_g - G = 25/(10^-2) - 20 = 2500 - 20 = 2480 Omega`