A galvanometer having coil resistance 10Ω shows a full scale deflection for a current of 3mA.

Question

A galvanometer having coil resistance \(10\Omega\) shows a full scale deflection for a current of 3mA. For it to measure a current of 8A, the value of the shunt should be:

(1) \(3 \times 10^{-3} \Omega\)

(2) \(4.85 \times 10^{-3} \Omega\)

(3) \(3.75 \times 10^{-3} \Omega\)

(4) \(2.75 \times 10^{-3} \Omega\)

Answer 1

The correct option is (3) \(3.75 \times 10^{-3} \Omega\)

\(S \times (8 - 0.003) = 0.003 \times 10\)

\(S = \frac{0.03}{7.997}\)

\(= 3.75 \times 10^{-3} \Omega\)