Combination Circuit Problem

  • Thread starter joeeykn245
  • Start date
  • #1

Homework Statement



Three identical resistors are connected in parralel. The equivalant resistance increases by 700 ohm when one resistor is removed and connected in series with the remaining two, which are still in parrallel. Find resistance of each resistor

Rt1 + 700ohms = Rt2

Homework Equations



(1/Rt) = (1/R1) + (1/R2) ... For a parallel Circuit

Rt = R1 + R2 ... For a series Circuit

The Attempt at a Solution



First, we made an equation for the initial parallel circuit

RT1 +700 = RT2
1/Rt1 =1/R + 1/R +1/R
1/Rt1=3/R

1/Rt = 3/R

R = 3Rt for later substitution

RT1 +700 = RT2
1/Rt1 =1/R + 1/R +1/R
1/Rt1=3/R

For the combination circuit..

RT2 = 2/R + R


We substituted the RT1 and RT2 into R's

RT1 +700 = RT2

R/3 + 700 = R/2 + R

After plugging it in, we get 600 for R. Is this correct?
 

Answers and Replies

  • #2
Filip Larsen
Gold Member
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276
Welcome to PF!

You can easily check that yourself by inserting the R=600 ohm into your expression for the resistance of the two circuits and see if they differ by 700 ohm. But yes, 600 ohm is correct.
 

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