Question
Chemistry Question on types of cells
Two cells each of same emf e but of internal resistances r1 and r2 are connected in series through an external resistance R. If the potential difference between the ends of the first cell is zero, what will be the value of R in terms of r1 and r2 ?
A
r1−r2
B
r1+r2
C
2r1−r2
D
2r1+r2
Answer
r1−r2
Explanation
Solution
Current in the circuit I=(r1+r2)+R2e and e−Ir1=0 ⇒e−(r1+r2)+R2er1=0 ⇒(r1+r2)+Rer2−er1+eR=0 ⇒r2−r1+R=0 or R=(r1−r2)