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PHYSICS

JAMB 2020 - Question 29

Physics 2020 JAMB Past Questions - Question 29: Four cells each of e.m.f 1.5V and internal resistance of 4Ω are connected in parallel. What is the effective e.m.f. and internal resistance of the combination?

Choose the correct answers from the options given.

Four cells each of e.m.f 1.5V and internal resistance of 4Ω are connected in parallel. What is the effective e.m.f. and internal resistance of the combination?

A: 6.0V, 16Ω

B: 6.0V, 1Ω

C: 1.5V, 4Ω

D: 1.5V, 1Ω

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Correct Answer

Explanation

Since all the cells are connected in parallel, the effective e.m.f. is just that of one single cell. Which means e.m.f. = 1.5V

However, the effective internal resistance adds as parallel arrangement given as
1/r = 1/r1 + 1/r2 + 1/r3 + 1/r4
= 1/4 + 1/4 + 1/4 + 1/4
= 1Ω
∴ r = 1Ω

Answer = 1.5V, 1Ω