Question

A galvanometer has a resistance of $25ohm$ and a maximum of $0.01A$ current can be passed through it. In order to change it into an ammeter of range $10A$, the shunt resistance required is

• A. $5/999ohm$
• B. $10/999ohm$
• C. $20/999ohm$
• D. $25/999ohm$

Answer 1

The correct option is D $25/999ohm$

Given a galvanometric coil

Resistance on galvanometer = $25\Omega$

Current on the galvanometer = $0.01A$

Ammmeter range = $10A$

From formula we know that,

$i_g=i\frac{S}{G+S}\Rightarrow 0.01=10\frac{S}{25+S}$

$\Rightarrow 1000S=25+S\Rightarrow S=\frac{25}{999}\Omega$