Two cells in series with a resistor: resistance for which one cell's terminal voltage is zero

1. A.
   $r_{1} + r_{2}$
2. B.
   $\frac{r_{1}}{2} - r_{2}$
3. C.
   $\frac{r_{1}}{2} + r_{2}$
4. D.
   $r_{1} - r_{2}$

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1. A.
   $r_{2} - r_{1}$
2. B.
   $r_{1} - r_{2}$
3. C.
   $r_{1}$
4. D.
   $r_{2}$

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1. A.
   $r_{1} - r_{2}$
2. B.
   $\frac{r_{1}r_{2}}{r_{1} + r_{2}}$
3. C.
   $\frac{r_{1} + r_{2}}{2}$
4. D.
   $r_{2} - r_{1}$

Tap an option to check your answer.