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 t

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

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