A galvanometer of resistance 100 Ω when connected in series with 400 Ω measures ​

Question

A galvanometer of resistance \(100 \ \Omega\) when connected in series with \(400 \ \Omega\) measures a voltage of upto \(10 \mathrm{~V}\). The value of resistance required to convert the galvanometer into ammeter to read upto 10 A is \(\mathrm{x} \times 10^{-2} \ \Omega\). The value of x is :

(1) 2

(2) 800

(3) 20

(4) 200

Answer 1

Correct option is : (3) 20

\( \begin{aligned} & \mathrm{ig}=\frac{10}{400+100} \\ & =20 \times 10^{-3} \end{aligned} \)

for Ammeter

\( \text { igR }=(i-i g) S\)

\(20 \times 10^{-3} \times 100=10 \times \mathrm{S}\)   

\( \mathrm{S}=200 \times 10^{-3} \Omega \)

\(20 \times 10^{-2} \Omega\)