A galvanometer of resistance \( 76\,\Omega \) gives full scale deflection when only 5% of total current passes through it. The value of shunt is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 4\,\Omega \)
A shunt is a small resistance connected in parallel with the galvanometer, so both have the same potential difference across them. If \( I \) is the total current, \( I_g \) passes through the galvanometer and \( I - I_g \) through the shunt.
\( \displaystyle I_g G = (I - I_g) S \;\Rightarrow\; S = \frac{I_g\,G}{I - I_g} \)
\( I_g = 0.05\,I \)
\( I - I_g = 0.95\,I \)
\( G = 76\,\Omega \)
\( \displaystyle S = \frac{0.05\,I \times 76}{0.95\,I} = \frac{76}{19} = 4\,\Omega \)