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. (a) $1 \Omega$ in series
• A. (b) 1 $\Omega$ in parallel
• A. (c) $0.1 \Omega$ in series
• A. (d) $0.1$ $\Omega$ in parallel

Answer 1

(b) 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

Where (Given)

For I = 5A, we get

$\frac { 1 / 60 } { 5 - ( 1 / 60 ) } = \frac { \mathrm { S } } { 300 } \Rightarrow \mathrm { S } = 1 \Omega$