Two cells of equal e.m.f. and of internal resistances $${{r}_{1}}$$ and $${{r}_{2}}({{r}_{1}}{{r}_{2}})$$ are connected in series. On connecting this combination to an external resistance R, it is observed that the potential difference across the first cell becomes zero. The value of R will be [MP PET 1985; KCET 2005; Kerala PMT 2005]

Question

Two cells of equal e.m.f. and of internal resistances $${{r}_{1}}$$ and $${{r}_{2}}({{r}_{1}}>{{r}_{2}})$$ are connected in series. On connecting this combination to an external resistance R, it is observed that the potential difference across the first cell becomes zero. The value of R will be [MP PET 1985; KCET 2005; Kerala PMT 2005]

TuteeHUB · Answer

$${{r}_{1}}+{{r}_{2}}$$

TuteeHUB · Answer

$${{r}_{1}}-{{r}_{2}}$$

TuteeHUB · Answer

3

TuteeHUB · Answer

$$\frac{{{r}_{1}}-{{r}_{2}}}{2}$$

1.	Two cells of equal e.m.f. and of internal resistances \[{{r}_{1}}\] and \[{{r}_{2}}({{r}_{1}}>{{r}_{2}})\] are connected in series. On connecting this combination to an external resistance R, it is observed that the potential difference across the first cell becomes zero. The value of R will be [MP PET 1985; KCET 2005; Kerala PMT 2005]
A.	\[{{r}_{1}}+{{r}_{2}}\]
B.	\[{{r}_{1}}-{{r}_{2}}\]
C.	3
D.	\[\frac{{{r}_{1}}-{{r}_{2}}}{2}\]
Answer» C. 3

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