Two cells A and B with same e.m.f of 2 V each and with internal resistances rA = 3.5 Ω and rB = 0.5 Ω are connected in series…

Q: Two cells A and B with same e.m.f of 2 V each and with internal resistances rA = 3.5 Ω and rB = 0.5 Ω are connected in series with an external resistance R = 3 Ω. Find the terminal voltages across the two cells.

Sol. Current through the circuit $\large i = \frac{E}{R+r}$

$\large i = \frac{2 + 2}{3 + 3.5 + 0.5} = \frac{4}{7} $

(i) R = 3 Ω , rA = 3.5 Ω , E = 2 V

Terminal voltages A , VA = E – i r

= 2 – (4/7) × 3.5 = 0 volt

(ii) rB = 0.5 Ω , R = 3 Ω , 2 V

Terminal voltage at B, VB = E-ir

= 2 – (4/7) × 0.5 = 1.714 volts.