Question

A galvanometer has a resistance of 30 and a current of 2ma is needed for a full scale deflection. The resistance that should be used to convert it into a voltmeter of 0.2v range is (1) 60

Answer 1

The given galvanometer can be converted into a voltmeter of range 0.2V by adding a series resistance of 70 Ω with it.

Explanation:

Let r be the series resistance added with the galvanometer.

so total resistance = r + 30 Ω

full scale current = 2mA = 0.002 A

Voltage range = 0.2 v

we know that resistance, R = voltage/current

=> r+30 = 0.2/0.002 = 100

=> r = 100-30 = 70 Ω

Hence a series resistance of 70 Ω should be added with the galvanometer to convert it into a voltmeter of 0.2v range.