Question

A moving coil galvanometer has 150 equal divisions . its current sensitivity is 10 divisions per mAand voltage sensitivity is 2 divisions per mV .in order that each division reads 1vthe resistance in ohm needed to be connected in series with the coil will be -
a.99995
b.9995
c.103
d.105

Answer 1

b is write answer OK

Answer 2

Current sensitivity = 10 division per mA

Ig = 150/10 mA = 0.015 A

voltage sensitivity = 2 divisions per mV

Vg = 150/2mV = 0.075 mV

Rg = 0.075/0.015 = 5 ohm

V = 150× 1 = 150 volt = full scale deflection.

Series resistance R

R = V/Ig−Rg = 150/0.015−5

= 9995 ohm

Option (b) is correct