Question

The following graph shows the potential difference across the terminals of a cell against its load current.

Find,

1. the emf of the cell and
2. the internal resistance of the cell.

Answer 1

I. The Emf of the cell is 6V, as when the load current is zero, the potential difference becomes equal to the emf of the cell.

II. The internal resistance of a cell can be determined as the negative slope of its voltage-current graph.

First, we can determine the slope by choosing two points on the line:

Slope = `(0 - 6)/(12 - 0)`

= `(-6)/12`

= −0.5

This means that the internal resistance must be 0.50 ohm (Ω).