Q. A candidate connects a moving coil ammeter $A$ and a moving coil voltmeter $V\ $ and a resistance R as shown in figure If the voltmeter reads 20 V and the ammeter reads $4\ A,\ then\ R$ is
A) Equal to 5 $\Omega$
B) Greater than 5 $\Omega$
C) Less than 5 $\Omega$
D) Greater or less than 5 $\Omega\ $depending upon its material
Explanation
(b) Here, $i = 4A;V = 20\ $ Volt; so,
$R = \frac{V}{I} = \frac{20}{4} = 5A.$ Since, voltmeter is connected in parallel with resistance $R,$ the effective resistance of this combination is 5 $\Omega$ only if the resistance R is greater than 5$\Omega$, since total resistance in parallel combination becomes less than individual resistance.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.