Question

A galvanometer has a resistance of 500$\Omega$ and a current of 0.01 amp will cause full scale deflection. To convert this into an ammeter with full scale deflection for 5A, we have to connect approximately a resistance of

• A. 1 $\Omega$ in Series
• B. 1 $\Omega$ in parallel
• C. 2 $\Omega$ in Series
• D. 2 $\Omega$ in parallel

Answer 1

Answer: (B)

1 $\Omega$ in parallel

$\frac{i_1}{i_2}=\frac{0.01}{5}=\frac{R_2}{R_1}$ (power loss in both the cases will be same)

$R_2=\frac{500x}{500+x};R_1=500$

= $=\frac{0.01}{5}=\frac{x}{500+x}$

5+0.01x=5x

4.99x=5

$x=1\Omega$