Two cells of emf 2 E and E with internal resistance r 1 and r 2 respectively are connected in series to an external resistor R (see figure). The value of R , at which the potential difference acro

Question

Two cells of emf 2 E and E with internal resistance r 1 ​ and r 2 ​ respectively are connected in series to an external resistor R (see figure). The value of R , at which the potential difference across the terminals of the first cell becomes zero is

TestHub · Accepted Answer

i = R + r 1 ​ + r 2 ​ 3 E ​ T . P . D . = 2 E − i r 1 ​ = 0 2 E = i r 1 ​ ⇒ 2 E = R + r 1 ​ + r 2 ​ 3 E × r 1 ​ ​ 2 R + 2 r 1 ​ + 2 r 2 ​ = 3 r 1 ​ R = 2 r 1 ​ ​ − r 2 ​

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