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Four cells each of e.m.f 1.5V and internal resistance of 4Ω are connected in paral...


Question

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?

Options

A) 6.0V, 16Ω

B) 6.0V, 1Ω

C) 1.5V, 4Ω

D) 1.5V, 1Ω


The correct answer is D.

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


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Dicussion (1)

  • 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

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