Wye-Delta and Series-Parallel Circuit Problem

  • Thread starter Thread starter terryds
  • Start date Start date
  • Tags Tags
    Circuit
AI Thread Summary
The discussion focuses on solving a circuit problem involving Wye-Delta transformations and calculating equivalent resistance and total current. The initial attempt incorrectly identifies the configuration of resistors, particularly misclassifying the 10 ohm, 5 ohm, and 3 ohm resistors as being in series when they are not. It is clarified that the 5 ohm and 3 ohm resistors are in series, while the 10 ohm resistor has a different current path. A suggested approach is to treat the 4 ohm, 8 ohm, and 10 ohm resistors as a Wye configuration and convert it to a Delta to simplify the calculations. Understanding the correct arrangement of resistors is crucial for accurate resistance calculations.
terryds
Messages
392
Reaction score
13

Homework Statement


2qv4kuh.jpg
Determine the equivalent resistance and the total current!

Homework Equations



Ohm's Law
Wye-Delta Transformation

The Attempt at a Solution


[/B]
I do the series on 10 ohm, 5 ohm, 3 ohm resistors, because it is node e-g,g-h,h-f, so it becomes 18 ohms (e-f). Then I do the parallel 18 ohms // 4 ohms = 3.272 ohms (node e-f).

Then, I do the series 8 ohms with 3.272 ohms then parallel it with 0.0263 ohms. Let's call this result R_a (node d-f)
Also, I do the series 2 ohms with 60 ohms then parallel it with 0.0526 ohms. Let's call this result R_b (node c-d)

Then, I do the series R_b with R_a = R_c (node c-f) which is parallel to 0.3157 ohms.

After doing the parallel calculation, I do the series with 4 ohms.
But, it turns out that it is wrong answer.

The question is: Where did I get wrong? Please help. (I already know the correct answer and the correct step; but I still couldn't understand where I got wrong)
 
Physics news on Phys.org
terryds said:
I do the series on 10 ohm, 5 ohm, 3 ohm resistors...
These three resistors are not in series. The 5 ohm and 3 ohm are in series.
 
  • Like
Likes terryds
lewando said:
These three resistors are not in series. The 5 ohm and 3 ohm are in series.

Alright, I understand!
It seems that I can't make it series because the current at 10 ohm is different than 5 ohm and 3 ohms!
 
To start, yes the 3Ω and 5Ω are in series, because at node h, ther is only one way for current to flow, but you cannot say the same about these two and 10Ω, because at node g, current has two directions it can flow. That is how you can make decisions if a resistor (or equivalent resistance) is in series with another resistor.
 
  • Like
Likes terryds
One option, would be to treat the 4Ω, 8Ω and 10Ω a Y, and turn that into an equivalent Delta, then proceed with those equivalents.
 
  • Like
Likes terryds
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top