A cell supplies a current of 0.6 A through a 2 ohm coil and a current of 0.3 A through an 8 ohm coil.Calcualte the emf and internal resistence of the cell

Let emf of cell be ε and internal resistace of cell is r.

 

for the 2Ω coil, 0.6×(2+r) = ε , 1.2+0.6r = ε ....................... (1)

for the 8Ω coil, 0.3×(8+r) = ε,  2.4+0.3r = ε ........................(2)

 

by equating (1) and (2) and solve for r, we get r = 4 Ω.

 

then from (1), by substituting r=4, we get emf ε = 3.6V