Question

A cell of emf  'E' and internal resistance 'r' is connected across a variable load resistor R. Draw the plots of the terminal voltage V versus (i) R and (ii) the current I.

It is found that when R = 4 ohm, the current is l A when R is increased to 9 ohm, the current reduces to 0.5 A. Find the values of the emf E and internal resistance r.

Answer 1

(i)

(ii)

From equation (i) and (ii)

4 + r = 4.5 + 0.5 r

therefore, r = 1 ohm

Using this value of r, we get

E = 5V