Question

Two cells of same emf but different internal resistances r 1 and r 2 are connected in series with a resistance R. The value of resistance R , for which the potential difference across second cell is zero, is

• A. r2 – r1
• B. r1 – r2
• C. r1
• D. r2

Answer 1

Answer: (A)

r2 – r1

Answer 2

The correct option is(A): r 2 – r 1.

$l=\frac{2ε}{R+r_1+r_2}$

As per the question,

$\frac{2ε}{R+r_1+r_2}×r_2-ε=0$

$⇒R=r_2-r_1$