Question

An ammeter $A$ reads $2A$ and the voltmeter $V$ reads $20V$. The value of resistance $R$ is (assuming finite resistances of ammeter and voltmeter)

• A. Exactly $10\Omega$
• B. Less than $10\Omega$
• C. More than $10\Omega$
• D. We cannot definitely say

Answer 1

The correct option is B Less than $10\Omega$

$V_{AB}=(I-I_g)\cdot R=I_g\cdot G$
where, $G=$ voltmeter resistance
$V_{AB}=20V$
$I=2A$ and $R=R$
$20=(2-I_g)\cdot R$
$R=\frac{20}{2-I_g}$
$\therefore R<10\Omega$