A cell of emf 'E'

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’.