Q. The reading of a high resistance voltmeter when a cell is connected across it is $2.2\ V.$ When the terminals of the cell are also connected to a resistance of $5\ \Omega$ the voltmeter reading drops to $1.8\ V.$ Find the internal resistance of the cell
A) $1.2\ \Omega$
B) $1.3\ \Omega$
C) $1.1\ \Omega$
D) $1.4\ \Omega$
Explanation
(c) $E = 2.2volt,\ V = 1.8\ volt,\ R = 5R$
$r = \left( \frac{E}{V} - 1 \right)R = \left( \frac{2.2}{1.8} - 1 \right) \times 5 = 1.1\Omega$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.