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.

Question

Philoid · Accepted Answer

After applying KCL in the above circuit we get,

E – Ir – IR = 0,

We know that V = IR,

So,

V = E -Ir

The graph of V v/s the current I is given as,

By the graph and the equation we can say that,

The Y intercept gives the emf of the cell ‘E’

The slope of the graph gives the value of internal Resistance ‘r’.