Question

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. $1.4 \Omega$

Answer 1

Answer: (C)

$1.1 \Omega$

Answer 2

$E = 2.2$ volt $R = 5 R$

$r = \left( \frac { E } { V } - 1 \right) R = \left( \frac { 2.2 } { 1.8 } - 1 \right) \times 5 = 1.1 \Omega$