Question

The range of voltmeter of resistance $300\, \Omega$ is $5 \,V$. The resistance to be connected to convert it into an ammeter of range $5\, A$ is

• A. $1\, \Omega$ in series
• B. $1\, \Omega$ in parallel
• C. $0.1\, \Omega$ in series
• D. $0.1\, \Omega$ in parallel

Answer 1

Answer: (B)

$1\, \Omega$ in parallel

Answer 2

A voltmeter is a galvanometer having a high resistance connected in series with it. The current through the galvanometer is $I_{g}=\frac{5\, V}{300\, \Omega}$ $=\frac{1}{60}\,A$ An ammeter is a galvanometer having a low resistance connected in parallel with it. The shunt resistance $S$ is determined from $\frac{I_{g}}{I-I_{g}}=\frac{S}{G}$ where $G = 300 \,\Omega$ (Given) For $I = 5\, A$, we get $\frac{1/ 60}{5-\left(1 /60\right)}$ $=\frac{S}{300}$ $\Rightarrow S=1\,\Omega$