Two Resistors in a Parallel Circuit

  • Thread starter Obsqura
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Homework Statement



Two resistors of X and Y are in parallel with one another and in series with a 200 Ω resistor and a battery whose emf is 1.5 volt and whose internal resistance is 0.5 Ω. The resistance of X is 100 Ω. When Y is disconnected from X, an additional resistance of 50 Ohms must be inserted in the circuit in order to keep the current through X is unchanged. Find the resistance of Y. Compute the value of Y again for the same case considering the internal resistance of the battery negligible.

Homework Equations



R1 = 200 Ω + 0.5 Ω + (XY/X+Y)
R2 = 200 Ω + 0.5 Ω + 50 Ω + X
R1 = R2

The Attempt at a Solution



In R1, X and Y are parallel, but in R2, Y is removed, so it is just in series (I think?). If the 50 Ω was just added in place of Y so they are still parallel, then Y would be 50 Ω and it doesn't seem right.

Since the resistance should still be the same, I set R1 and R2 equal to eachother to get:

200.5 + 100Y/(100+Y) = 350.5
I then solved for Y to get Y = 100

Am I solving this correctly? I thought I would need the 1.5V in an equation and compared to the rest of the problems I am doing, this seems much easier. Any help is appreciated. Thanks.
 

Answers and Replies

  • #2
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From what I understand this is correct. The reason for the voltage being given so that you may prove that your calculations are correct with the formula.

I = V/R

since if I1 = I2 then they have equivalent resistance in the circuit.

I1 being the equation with y
I2 without y and with the added 50ohms

Just an heads up you may need to check your math. It doesn't seem to compute when you plug it back in.
 
Last edited:

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