Question
Thu February 28, 2013 By: Mrinal
 

Two cells of different emfs and internal resistance are connected in parallel with one another. Find the expression for the equivalent internal resistance of the combination?

Expert Reply
Thu February 28, 2013

Cells In Parallel: In parallel grouping all anodes are connected at one point and all cathodes are connected together at other point. If n identical cells are connected in parallel

(i) Equivalent emf Eeq = E

(ii) Equivalent internal resistance Req = r/n

(iii) Main current i = E/R+r/n

(iv) Potential difference across external resistance = p.d. across each cell = V = iR

(v) Current from each cell i' = i/n

(vi) Power dissipated in the circuit P = (E/R+r/n)2 R

(vii) Condition for max. power is R = r/n and Pmax = n(E2/4r)

(viii) This type of combination is used when nr > > R

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