Two batteries of emf ε1 and ε2 (ε2>ε1) and internal resistances r1 and r2 respectively are connected in parallel as shown in the figure.

         

1. The equivalent emf εeq of the two cells is between ε1 and ε2. i.e, ε1<εeq<ε2
2. The equivalent emf εeq is smaller than ε1
3. The εeq is given by εeq=ε1+ε2 always
4. εeq is independent of internal resistances r1 and r2

(a) Hint: Use the concept of the parallel combination of cells.

Step 1:

The equivalent emf of this combination is given by:

εeq=ε2r1+ε2r2r1+r2

Step 2:

This suggests that the equivalent emf εeq of the two cells is:

ε1<εeq<ε2