COMEDK · Physics · 19. Current Electricity
Two cells with the same emf \(E\) and different internal resistances \(r_1\) and \(r_2\) are connected in series to an external resistance \(R\). If the potential difference across the first cell is zero then value of \(R\).
- A \(\sqrt{r_1 r_2}\)
- B \(r_1-r_2\)
- C \(\dfrac{r_1+r_2}{2}\)
- D \(r_1+r_2\)
Answer & Solution
Correct Answer
(B) \(r_1-r_2\)
Step-by-step Solution
Detailed explanation
The total emf of the two cells connected in series is \(E_{total} = E + E = 2E\). The total resistance of the circuit is \(R_{total} = R + r_1 + r_2\). The current \(I\) flowing through the circuit is given by \(I = \dfrac{2E}{R + r_1 + r_2}\). The potential difference \(V_1\)…
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