Data: L = 4 m, R = 8 Ω, E = 2V, r = 0,
R(shunt) = 15 Ω, l = 217 cm = 2.17 m,
l1 = 217 – 17 = 200 cm = 2 m
potential gradient,
K = \(\cfrac VL\) = \(\cfrac{ER}{(R+r)L}\)
= \(\cfrac{2\times8}{(8+0)\times4}\) = 0.5 V/m
If the emf of the cell is E1,
E1 = KI
= 0.5 x 2.17 = 1.085 V
The internal resistance of the cell is
r(cell) = R(shunt)\(\left(\cfrac{I}{I_1}-1 \right)\)
= 15 \(\left(\cfrac{217}{200}-1 \right)\) = 15 x 0.085
= 1.275 Ω