Question

A candidate connects a moving coil voltmeter $V$, a moving coil ammeter $A$ and a resistance $R$ as shown in figure. If the voltmeter reads $20V$ and the ammeter reads $4A,R$ 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

Answer 1

Answer: (B)

Let a current of $x$ amperes passes through the voltmeter, then $(4-x)$ amperes passes through the resistance $R$. Therefore, voltmeter reading $20=(4-x)R$
$\therefore R=\frac{20}{4-x}$, i.e., $R>5\Omega$