Final answer:
The terminal voltage is 0.5V and the external resistance is approximately 0.17 ohms for a cell with an EMF of 2V and internal resistance of 0.5 ohms delivering a current of 3A.
Step-by-step explanation:
The terminal potential difference (p.d.) of the cell can be calculated using the formula V = EMF - Ir, where 'V' is the terminal voltage, 'EMF' is the electromotive force, 'I' is the current, and 'r' is the internal resistance. For a cell with an EMF of 2 volts and internal resistance of 0.5 ohms delivering a current of 3 A, the terminal voltage is V = 2V - (3A × 0.5Ω) = 0.5V. To calculate the external resistance 'R', we use Ohm's law V = IR, which gives us R = V/I. Therefore, the external resistance is R = 0.5V / 3A = 0.1667Ω, or approximately 0.17Ω.