Question

An ammeter has a range of 1A and an internal resistance of 0.1$\Omega$. If another shunt of 0.1$\Omega$ is connected across its terminals, its new range is

• A. 2A
• B. 1.5A
• C. 1.8A
• D. 2.4A

Answer 1

The correct option is A 2A

Given : Current in the ammeter $=1A$

Internal resistance of the ammeter $=0.1\Omega$

Resistance of shunt connected $=0.1\Omega$

Voltage across the ammeter at $1A=0.1\times 1=0.1V$

When another shunt is connected, new resistance of the ammeter $=\frac{(0.1\times 0.1)}{(0.1+0.1)}$$=\frac{0.01}{0.2}=\frac{1}{20}$

So, the current in the ammeter $=\frac{0.1}{\frac{1}{20}}=2A$