Question

n identical cells, each of emf E and internal resistance r, are joined in series to form a closed circuit.

The potential difference across any one cell is:

(a) E

(b) E/n

(c) (n-1)/n E

(d) Zero

Solution

Current in circuit, i = (nE)/(nr)= E/r

The equivalent circuit of one is shown in figure.

Potential difference across the cell = V_A-V_B= -E+ir

=> V_A-V_B= -E + (E/r)r= -E+E=0

Therefore, option (D) is correct .