# A cell of unknown emf E and internal resistance R1 and R2 (R2>R1) and a perfect ammeter are given. The current in the circuit is measured in five different situations: (1) Without any external resistance in the circuit, (2) With resistance R1only, (3)With resistance R2 only,(4) With R1 and R2 used in series combination and (5) With R1 and R2 used in parallel combination. The current obtain in five cases are 0.42A, 0.6A, 1.05A,1.4A and 4.2A, but not necessarily in that order. Identify the currents in the five cases listed above and calculate E,r,R1 and R2.

Aman Bansal
592 Points
12 years ago

dear shiksha,

Total resistance in the five cases are :

r , r+  R1R2/(R1+R2) , r+R2 , r + R2 ,  r+R1+R2

The correct order of  values of I are : 4.2A, 1.4A, 1.05 A, 0.6 A and 0.42 A ½
Also

Solve first four to obtain, E = 4.2V, r = 1 , R1 = 3 , R2 = 6

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