Question

The combination of two identical cells, whether connected in series or parallel combination provides the same current through an external resistance of 2 Ω. The value of internal resistance of each cell is

• A. 2 Ω
• B. 4 Ω
• C. 6 Ω
• D. 8 Ω

Answer 1

The Correct Option is A

The correct answer is (A) : 2 Ω

Fig. 1

Fig. 2

From above diagram, we get
\(i_p = \frac{E}{2+\frac{r}{2}} \) and \(i_s = \frac{2E}{2+2r}\)
given \(i_p = i_s\)
\(\frac{1}{2+\frac{r}{2}} = \frac{1}{1+r}\)
\(1 + r = 2 + \frac{r}{2}\)
r = 2Ω