A galvanometer of resistance 520 Ω is shunted with 20 Ω 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 Ω
Given:
Galvanometer resistance, $G = 520\,\Omega$
Shunt resistance, $S = 20\,\Omega$
Equivalent resistance of the ammeter:
$R_A = \frac{G \times S}{G + S}$
$R_A = \frac{520 \times 20}{520 + 20} = \frac{10400}{540} = 19.26\,\Omega$
∴ The resistance of the ammeter is $19.26\,\Omega$.