Question

A student connects an ammeter $A\,$ and a voltmeter $V\,$ to measures a resistance $R\,$ as shown in figure. If the voltmeter reads $20\,V$ and the ammeter reads $4A,$ then the value of $R\,$ is :- (voltmeter and ammeter are not ideal)

• A. Equal to $5\,\Omega$
• B. Greater than $5\,\Omega$
• C. Less than $5\,\Omega$
• D. Greater or less than $5\,\Omega$ depending upon the
  direction of current

Answer 1

Answer: (C)

As the given ammeter and voltmeter are not considered ideal, we use
$4\left(R + R_{A}\right)=20\,$
$R=5-R_{A};R_{A} \rightarrow $ Resistance of ammeter