Question

The deflection in a moving coil galvanometer falls from 50 divisions to 10 divisions,when a shunt of $ 20\Omega$ is connected with it. The resistance of galvanometer coil is

• A. $ 24\Omega$
• B. $ 12\Omega$
• C. $ 6\Omega$
• D. $ 48\Omega$

Answer 1

Answer: (D)

Here let the value of current from one division be i A.
Thus the current through ammeter $I =50 i$ and through Galvanometer $I _{ g }=10 I$
$S =\frac{ Ig _{ g }}{ I - I _{ g }} G $
$\Rightarrow G =\frac{ I - I _{ g }}{ I _{ g }} S $
$=\frac{50 i -10 i }{10 i } \times 12 \Omega $
$=4 \times 12 \Omega $
$=48 \Omega$