JAMB - Physics (2011 - No. 23)
Three similar cells each of e.m.f 2 v and internal resistance 2Ω are connected in parallel, the total e.m.f and total internal resistance are respectively
6 v, 6.0Ω
2 v, 0.7Ω
2 v, 6.0Ω
6 v, 0.7Ω
Explanation
Total energy in parred connection is equal to emt of one cell, = 2v but total internal resistance is given by
(1)/r = (1)/r1 + (1)/r2 + (1)/r3 = (1)/2 + (1)/2 + (1)/2 = (3)/2
∴ r = (2)/3 = 0.67Ω
(1)/r = (1)/r1 + (1)/r2 + (1)/r3 = (1)/2 + (1)/2 + (1)/2 = (3)/2
∴ r = (2)/3 = 0.67Ω
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