Question

The current flowing in the primary circuit of potentiometer is 2A and the resistance of its wire is $0.2\Omega /m$. If a one ohm standard coil gets balanced at 250 cm length of the wire, then the current flowing in the coil will be

• A. 0.1A
• B. 1A
• C. 1.5A
• D. 0.05A

Answer 1

The correct option is B 1A

Total resistance of balancing length of wire = $0.2\times 2.5\Omega =0.5\Omega$

For balancing condition, potential difference across the end of both wire and coil is same

Hence $I_{coil}{R}_{coil}=I_{wire}{R}_{wire}$

$I\times 1=2\times 0.5=1A$