The internal resistance of a cell of emf 2 V is 0.1 Ω. It is connected to an external resistance of 3.9 Ω. The terminal potential difference across the cell will be
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 1.95 V
Given:
EMF of the cell, $E = 2 \text{ V}$
Internal resistance, $r = 0.1\ \Omega$
External resistance, $R = 3.9\ \Omega$
Total resistance in the circuit:
$R_{\text{total}} = R + r = 3.9 + 0.1 = 4\ \Omega$
Current in the circuit:
$I = \frac{E}{R + r} = \frac{2}{4} = 0.5\ \text{A}$
Terminal potential difference across the cell:
$V = E - Ir = 2 - (0.5 \times 0.1) = 2 - 0.05 = 1.95\ \text{V}$