A galvanometer of resistance \( 520\,\Omega \) is shunted with \( 20\,\Omega \) resistance to convert it into an ammeter. The resistance of the ammeter will be
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \( 19.3\,\Omega \)
A shunt is connected in parallel with the galvanometer, so the resistance of the ammeter is the parallel combination of the galvanometer resistance \( G \) and the shunt \( S \).
\( \displaystyle R_{A} = \frac{G\,S}{G + S} \)
\( \displaystyle R_{A} = \frac{520 \times 20}{520 + 20} = \frac{10400}{540} = 19.3\,\Omega \)