#### Question

A cell of emf 'E' and internal resistance 'r' is connected across a variable resistor 'R'. Plot a graph showing variation of terminal voltage 'V' of the cell versus the current 'I'. Using the plot, show how the emf of the cell and its internal resistance can be determined.

#### Solution

Terminal voltage 'V' of the cell is V = E − Ir

E is the emf of the cell, r is the internal resistance of the cell and I is the current through the circuit.

So, V = −Ir+E

Comparing with the equation of a straight line *y* = m*x*+c, we get:

*y* = V; *x* = I; *m* = −r; c = E

Graph showing variation of terminal voltage 'V' of the cell versus the current 'I' is

Emf of the cell = Intercept on V axis

Internal resistance = slop of line.

Is there an error in this question or solution?

Solution A Cell of Emf 'E' and Internal Resistance 'R' is Connected Across a Variable Resistor 'R'. Plot a Graph Showing Variation of Terminal Voltage 'V' of the Cell Versus the Current 'I'. Concept: Cells, Emf, Internal Resistance.