Question

A cell has electromotive force \(1.5\) volt and internal resistance \(0.2\) ohm. It is connected with an external resistance of \(2.8\) ohm. Calculate (i) the potential difference across the open ends of the cell and (ii) the current obtained from the cell.

Hint:

Always include internal resistance when calculating the total circuit resistance in practical cells.

Answer 1

Step 1: Using Ohm's Law, total resistance is: \[ R_{\text{total}} = 0.2 + 2.8 = 3 \, \Omega \] Step 2: The current obtained from the cell: \[ I = \frac{E}{R_{\text{total}}} = \frac{1.5}{3} = 0.5 \, A \] Step 3: Potential difference across the terminals: \[ V = E - Ir = 1.5 - (0.5 \times 0.2) \] \[ = 1.4 \, V \] \[ \therefore \text{The correct answers are } 1.4 \, \text{V and } 0.5 \, \text{A}. \] \[ \boxed{1.4 \, \text{V}, \, 0.5 \, \text{A}} \]