Question

When two identical cells are connected either
in series or in parallel across 2 ohm resistor
they send the same current through it. The
internal resistance of each cell is
1) 2 ohm 2) 1.2 ohm 3) 12 ohm 4) 21 ohm​

Answer 1

Sources in series:

I = 2V/(2R+4) ………… 1

Sources in parallel:

I = V/(R/2 + 4) ……… 2

Putting 1 = 2 and simplifying gives:

2V/(R+8) = 2V/(2R +4)

From which 2R + 4 = R + 8

Therefore R = 4 ohms