Question

In the circuit shown, the readings of ammeter and voltmeter are $4A$ and $20V$ respectively. The meters are non ideal, then $R$ is:

• A. $5\Omega$
• B. greater than $5\Omega$
• C. Less than $5\Omega$
• D. between $4\Omega$ and $5\Omega$

Answer 1

The correct option is B greater than $5\Omega$

Ammeter gives reading $4A,$ and both ammeter and voltmeter is not ideal, Thus voltmeter draws extra current say ${}^{\prime }{x}^{\prime }$

So, According to Kirchoff's law the current passing through resistance would be ${}^{\prime }4-x^{\prime }$ therefore, resistance $R=\frac{20}{(4-x)}$

where $x>0$ So $R>5$