Question

a moving coil galvanometer has a resistance of 25 and gives a full scale deflection for a current of 10 ma. How will you convert it into a voltmeter having range 0 100 v.

Answer 1

Given G=25, lg=10mA=10×10power by 3A, v=100V

To find resistance(Rs)

Formula R's=V/lg-G

Calculations by formula

R's=100/(10××10^(-3) -25

10000-25

9975

Ans- resistance by 9975

Answer 2

To connect it with a series a resistance of 9975 ohms should be given

Resistance of the coil = g = 25  (Given)

Current of the coil = Ig = 10mA = 10 × 10³ (Given)

Range of the voltmeter = V = 100  (Given)

Resistance = R = V/Ig - G

Therefore,  

R = 100 / 10 × 10³ - 25

= 10`4 - 25

= 10000 - 25

= 9975

Thus, a resistance of 9975 ohm is required.