Two cells with the same emf E and different internal resistances r1 and r2 are connected in series to an external resistance R. The value of R so that the potential difference across the first cell be zero, is
A
r1r2
B
r1+r2
C
r1−r2
D
2r1+r2
Medium
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Updated on : 2022-09-05
Solution
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Correct option is C)
The two cells have potential E each and respective internal resistance r1 and r2.
Let the current flowing in the circuit be i.
Using Kirchhoff's voltage law:
⇒−E+ir1+iR−E+ir2=0
⇒i=(R+r1+r2)2E
Potential across first cell, VAB=ir1−E=(R+r1+r2)2Er1−E