AP EAMCET · PHYSICS · Current Electricity
Two identical cells gave the same current through an external resistance of \(2 \Omega\) regardless whether the cells are grouped in series or parallel. The internal resistance of the cells is
- A \(1 \Omega\)
- B \(0.5 \Omega\)
- C \(1.5 \Omega\)
- D \(2.0 \Omega\)
Answer & Solution
Correct Answer
(D) \(2.0 \Omega\)
Step-by-step Solution
Detailed explanation
For first case, \(I=\frac{2 E}{R+2 r}\)...(i) For second case, \(I=\frac{E}{R+\frac{r}{2}}=\frac{2 E}{2 R+r}\)....(ii) From eqs(i) and (ii), we get \(\mathrm{R}+2 \mathrm{r}=2 \mathrm{R}+\mathrm{r} \Rightarrow \mathrm{r}=\mathrm{R}=2 \Omega\)
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