Question

In the circuit shown below, the ammeter and the voltmeter readings are $3A$ and $6V$ respectively. Then the value of the resistance $R$ is:

• A. $2\Omega$
• B. $>2\Omega$
• C. $<2\Omega$
• D. $\ge 2\Omega$

Answer 1

The correct option is C $<2\Omega$

For an ideal circuit, the resistance will come out to be simply $R=\frac{V}{I}=\frac{6}{3}=2\Omega$

However, for a non-ideal ammeter, resistance of ammeter is not zero and hence, measured voltage is the sum of voltages across ammeter and resistance. In other words, measured voltage($V$) is more than the actual voltage across the resistor($V_R$) or $V>V_R$.

Hence, measured resistance ($2\Omega$) is more than the actual resistance.