Question

A galvanometer having a coil resistance of $60O$ shows full scale deflection when a current of 1.0 A passes through it. It can be converted unto an ammeter to read currents upto 5.0 A by

• A. putting in parallel a resistance of $240O$
• B. putting in series a resistance of $15O$
• C. putting in series a resistance of $240O$
• D. putting in parallel a resistance of $15O$

Answer 1

Answer: (D)

putting in parallel a resistance of $15O$

Answer 2

$i G=(I-i) S$ where $G$ is the galvanometer resistance and $S$ is the shunt used with the ammeter.
$1.0 \times 60=(5-1) S$ where $S$ is the shunt used to read a $5 A$ current when the galvanometer can stand by $1 A$.
$S=\frac{1.0 \times 60}{4}=15 \Omega$ in parallel.