According to the question E−Ir1=0 and I=r1+r2+RE+E ∴r1E=r1+r2+R2E⇒r1+r2+R=2r1−r2⇒R=r1−r2
Two cells, having the same e.m.f. are connected in series through an external resistance R. Cells have internal resistances r1 and r2(r1>r2) respectively. When the circuit is closed, the potential difference across the first cell is zero. The value of R is:
Held on 30 Apr 2006 · Verified 9 Jul 2026.
r1+r2
r1−r2
2r1+r2
2r1−r2
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