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In an electric circuit, two resistors with resistances x and

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Re: In an electric circuit, two resistors with resistances x and [#permalink]

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New post 04 Sep 2017, 03:27
Shiv2016 wrote:
Bunuel

Why are we not considering r= x+y as it is mentioned that r is the combined resistance? Is it because we don't know how they are connected.


The question clearly gives the relationship between r, x, and y and it is NOT r = x + y: the reciprocal of r is equal to the sum of the reciprocals of x and y.
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Re: In an electric circuit, two resistors with resistances x and [#permalink]

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New post 04 Sep 2017, 03:35
Ans is simply D

kind of physics problem
R1 is first resistance R2 is another
if they are in series then R equivalent is R1+R2

if they are in parallel R equivalent is R1R2/(R1+R2)
so r1=x and r2=y therefore , xy/(x+y) is the answer... Ans is D



Also by what is given in ques

1/r = 1/x + 1/y
r = xy/ (x+y)

hence D
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Re: In an electric circuit, two resistors with resistances x and   [#permalink] 04 Sep 2017, 03:35

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