Question

A cell of e.m.f. 1.5 V is connected to an external resistance of 2.0 Ω, when p.d. recorded at the ends of the resistance is 1.2 V. Calculate the internal resistance of the cell.

Answer 1

E = 1.5 V; V = 1.2 V; R = 2.0 Ω; r = ?

$$r = \frac{R(E - V)}{V}$$

$$= \frac{2.0(1.5 - 1.2)}{1.2}$$

$$= \frac{2.0 \times 0.3}{1.2}$$

$$= 0.5 \ \Omega$$