Question

A galvanometer having a coil resistance of 100 $\Omega$ gives a full scale deflection when a current of $1mA$ is passed through it. The value of the resistance which can convert this galvanometer into an ammeter giving a full scale deflection for a current of $10A$, is

• A. $0.01\Omega$
• B. $2\Omega$
• C. $0.1\Omega$
• D. $3\Omega$

Answer 1

The correct option is A $0.01\Omega$

When full-scale current is flowing, potential difference
$V={10}^{-3}\times 100=0.1V$

Let shunt resistance be $R$. Current flowing through $R$ in full scale reading is $I_{sh}=10-0.001=9.999A$

$V=I_{sh}R$
$0.1=9.999R$
$R\approx 0.01\Omega$