Potential difference across parallel circuits

[belliott4488]

Thank you Bruce. I understand your point here.

So my mistake to begin with is, that electrical potential takes precedence first, hence we see the same potential difference across a parallel circuit (and their components). So my argument is somewhat incorrect to begin with as I had an incorrect starting point to my argument.

Thanks for clearing that up :)

No problem. I think you've got it now.

And oh, the lower the resistance, the higher the amount of energy dissipated (in the parallel circuit). Am I right to say that?

Oops - yeah, I think I might have misstated that. Lower resistance -> higher current -> greater power dissipation. I got thrown off by my friction analogy.

For the water analogy, is there somewhat a problem with the analogy given? As in the pre-requisites for the water pipes in order for the water pressures to be applicable (applicable as an analogy) for the electric circuit problem?

I'll have to let someone else answer that ... I'm not a big fan of the water analogy, despite its common use for problems like this.
- Bruce

 

[truewt]

No problem. I think you've got it now.

Oops - yeah, I think I might have misstated that. Lower resistance -> higher current -> greater power dissipation. I got thrown off by my friction analogy.


I'll have to let someone else answer that ... I'm not a big fan of the water analogy, despite its common use for problems like this.
- Bruce

Ahhh. I don't think you gave me a wrong impression. But its just that the lower the resistance, its only intuitive that the power dissipated is smaller. But its not the case in parallel circuits

 

[FrogPad]

Ahhh. I don't think you gave me a wrong impression. But its just that the lower the resistance, its only intuitive that the power dissipated is smaller. But its not the case in parallel circuits

Found a good link for yah... http://hyperphysics.phy-astr.gsu.edu/hbase/electric/watcir.html

click on components of the DC circuit

 

[belliott4488]

Ahhh. I don't think you gave me a wrong impression. But its just that the lower the resistance, its only intuitive that the power dissipated is smaller. But its not the case in parallel circuits

Wait a minute! That's what's wrong. Lower resistance -> more current -> MORE power dissipated!

This is something I used to get backwards, until I got my intuition fixed. A larger resistance does NOT present a larger load to a voltage source, despite what you'd think based on the wording. This is clear if you just think in extremes - an open circuit presents an infinite resistance but no load at all, whereas a short-circuit presents zero resistance and generally fries things (too high a load).

 

[truewt]

Thank you Frogpad. That analogy helped, but there are still points that I'm still unsure of.

We're taking potential energy into account? What about Bernouli's principle, where the pressure changes due to the change in water flow rate? The flow rate is changing throughout its flow, am I right?

 

[truewt]

Wait a minute! That's what's wrong. Lower resistance -> more current -> MORE power dissipated!

This is something I used to get backwards, until I got my intuition fixed. A larger resistance does NOT present a larger load to a voltage source, despite what you'd think based on the wording. This is clear if you just think in extremes - an open circuit presents an infinite resistance but no load at all, whereas a short-circuit presents zero resistance and generally fries things (too high a load).

Ahh I do know that. The intuition is wrong. Haha

 

[truewt]

Imagine a water pump hooked up to two pipes, in a configuration as like the one below with my beautiful ASCII art.

---W------________======B=======
|--------|___A___//_______________\\
|--------|======__________________=====D===
|--------|_______\\_______________//
----------________======C=======


If the water pump is W, and B and C are equal pipes. What would be the water pressure through A? What about the pressure at B and C. How would the flow of water change through B and C? What would the flow through A be compared to D?

Hey Frogpad, some problems with understanding the water analogy (again).

Alright. So by Bernoulli's Principle, in order for pressure to decrease (potential in electric circuit), the speed of the water must increase.

If we input resistances such as water wheels in pipes B and C, when water flows past these water wheels, the kinetic energy decreases, and hence speed decreases and hence pressure increases?!

Why is this so? It's so strange.

Even if we accommodate by inputting pipes of smaller radius after the wheel, the speed will increase (mass flow rate remains the same). But it just seem illogical!