Question

A galvanometer of resistance 80 ohm, shunted by a resistance of 20 ohm is joined in series with a resistance of 200 ohm and cell of emf 1.5V What is the sensitivity of the galvanometer if it shows a deflection of 30 divisions.

Answer 1

sensitivity = deflection/ current passed through galvanometer
given, deflection =urrent c30
to find current through galvanometer
net resistance = 20ohm|| 80ohm series 200ohm
= 216ohms.
net current from battery = v/net resistance
=1 /216 = 0.00694 amp
curent through galvanometer;
by current divider fromula i = 20/(20+80) * 0.00694 amp = 0.001388amp

sensitivity = deflection/ current passed through galvanometer
= 30 / 0.001388 = 21739.13
if u consider galvanometer to be together with the shunted part
sensitivity =deflection / current passed through galvanometer
= 30/0.00694 = 4322.76