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Help a Retard Understand

Anonymous Fri 08 Oct 02:19:12 2021 No.13727425 View Reply Original Report

Quoted By: >>13727447 >>13727453 >>13727522 >>13727824 >>13728657 >>13729577 >>13729754

Moving a heavy object is more work than moving a light box the same distance.
Assuming electrical resistance (load?) is equivalent to the weight of the box, then a circuit with more resistance is capable of more work than a circuit with less resistance.

The more current flows through a circuit, the more work is being done.
Yet current is varies inversely with resistance.

For example, an electrical filament will only get hot if it has some non-zero resistance.
If it has zero resistance then it will generate no heat, yet the current is high implying more work is being done.
Yet if the filament has high resistance, less current will flow and therefore the filament will not heat up and less work is being done.

I am a retard. Can any of you eggheads explain this apparent paradox in a way I terms I might be able to understand?

Anonymous

Anonymous Fri 08 Oct 2021 02:27:20 No.13727444 Report

Quoted By:

it's simple: there's no such electrical filament

Anonymous

Anonymous Fri 08 Oct 2021 02:28:19 No.13727447 Report

Quoted By:

>>13727425
>>13727425
>The more current flows through a circuit, the more work is being done.
>Yet current is varies inversely with resistance.
I could be off the mark here, but I am pretty sure your issue is here. Regardless of resistance x volts of electricity will always produce the same amount of work. The issue is what kind of work do you want the electricity to do.

Do you want it to get really fucking hot? Then you want thin wires with high resistance. Do you want to transfer it long distances? Then you want thick wires with low resistance.

Low resistance had more "work energy" only because it all gets to where you want. Where as high resistance wires are busy turning that "useful work energy" into thermal enregy.

Anonymous

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Anonymous Fri 08 Oct 2021 02:30:40 No.13727453 Report

Quoted By: >>13728663

>>13727425

Anonymous

Anonymous Fri 08 Oct 2021 03:05:42 No.13727522 Report

Quoted By: >>13727529 >>13727551

>>13727425
Current is how fast the electrons are moving, which is why it's measured in coulombs/second=amps. If the resistance is high then the electrons move slowly and generate less energy. If the resistance is low then the electrons move quickly. Faster moving electrons means more energy.

Anonymous

Anonymous Fri 08 Oct 2021 03:08:09 No.13727529 Report

Quoted By:

>>13727522
also, $P=I^2R$ so higher resistance does mean there is more energy in systems with the same current and different resistances.

Anonymous

Anonymous Fri 08 Oct 2021 03:16:37 No.13727551 Report

Quoted By: >>13728679

>>13727522
I hate to samefag again, but it isn't *literally* how fast they are moving but how many electrons are moving through every second, I just find it more intuitive to think of it as speed rather than the amount of electrons that get through. Either someone will correct me or you'll be misled because I didn't elaborate on my metaphor.

Anonymous

Anonymous Fri 08 Oct 2021 03:25:00 No.13727579 Report

Quoted By:

to stick with your analogy, low resistance is a heavy object, high resistance is a light object

Anonymous

Anonymous Fri 08 Oct 2021 04:30:40 No.13727824 Report

Quoted By:

I am not an electrical engineer so take explanation with a grain of salt
>>13727425
>If it has zero resistance then it will generate no heat, yet the current is high implying more work is being done.
This is not true. If an object has literally no resistance, no work is being done to retard the charge motion. You can apply literally any strength electric field to the object and have any current you want flow through the object and it will never heat up because the charges will never lose energy due to resistive forces, which is what creates the heat. You can apply any amount of initial work to the system and it will dissipate 0 power
>Yet if the filament has high resistance, less current will flow and therefore the filament will not heat up and less work is being done.
Yes, power dissipated depends on relationship between applied voltage and load resistance. It's a balance. If voltage/current is extremely high and resistance is basically 0, pretty much no power is dissipated. If voltage/current is basically 0 and resistance is extremely high, there's functionally no charge motion to retard and so negligible power is dissipated. It's in-between these scenarios where you will produce alot of heat

Anonymous

Anonymous Fri 08 Oct 2021 12:05:39 No.13728657 Report

Quoted By: >>13728923

>>13727425
https://en.wikipedia.org/wiki/System_equivalence
https://en.wikipedia.org/wiki/Analogical_models#Dynamical_analogies

If you want to think in analogies, then the electrical analog of 'physical mass' would be inductance, and resistance is more like a damper.

More mass -> hits like a truck, less mass->hits like a chicken
More water(as a medium) -> dampens your energy, just like resistance, air(as a medium) ->dampens your movement less

Anonymous

Anonymous Fri 08 Oct 2021 12:07:30 No.13728663 Report

Quoted By:

>>13727453
hint: the current doesn't change, because while the speed of the water is faster, the diameter is smaller.

Anonymous

Anonymous Fri 08 Oct 2021 12:11:52 No.13728679 Report

Quoted By:

>>13727551
big current= a fuckton of electrons pass through a diameter (kind of like how one alpha particle doesn't kill you, but 10^30 probably does, of course this all in the same time-interval)
small current=a smaller amount of electrons pass through a diameter
big voltage=every electron that we talk about has big energies and they can jump big distance
small voltage=every electron that we talk about has small energies and they can't jump that big

Anonymous

Anonymous Fri 08 Oct 2021 14:21:44 No.13728923 Report

Quoted By: >>13729860

>>13728657
>>13728657
Thanks for the references. Maybe my original analogy wasn't right. If the mass is analagous to inductance it makes more sense at least with electrical motors. If the motor is stopped it draw higher current than if the motor is rotating. A stopped motor does not produce back-EMF and therefor less "impedance?/resistance?" thereby causing more current draw and also creating more mechanical torque and also generating more heat in the windings which may also ruin the motor. In the case of a motor the mass or force in a mechanical system is directly analagous to impedance although apparently in an inverse way?

Although for example light bulbs do not work by inductance, only resistance. So for a given voltage I would assume that there is an ideal resistance, somewhere between 0 Ohms and infinity Ohms where the maximal amount of heat energy is dissipated. How would you find this optimum resistance for a light bulb?

Anonymous

Anonymous Fri 08 Oct 2021 17:42:19 No.13729577 Report

Quoted By:

>>13727425
The work analogy is pretty good because work in terms of force is:
$W=F*d$
Where work is like power, force is like the voltage and the distance is like the resistance.

If you don't move at all, you haven't done any work. Superconductors lock magnets in place because when there's zero resistance, there's infinite current.

t. Electronics engineer

Anonymous

Anonymous Fri 08 Oct 2021 18:41:59 No.13729754 Report

Quoted By:

>>13727425
So in other words you don't understand why a light bulb produces light because when resistance is high, no work/less work is being done. Conservation of energy applies to electromagnetic forces so you can look at a light bulb in terms of this. The total energy for an incandescent light bulb is sqrt3×V×iWhen you have a filament in series with this, the resistivity of the tungsten filament is determined by the innate conductivity of tungsten itself alongside the cross sectional area and length of the filament. Knowing these you can calculate for the resistance of the filament as a load. The physical properties of tungsten reveals that it can withstand extremely high temperatures without degrading its structure so once the material itself becomes hot enough from it throttling back the total energy of the power supply, photons are radiated from the electrons in the material. Work is being done on the filimanent itself in high enough quantity to transfer enough energy to the electrons in order for those electrons to emit photons. Remember that electrons drift through materials and in doing so transfer their energy as they collide with other atoms and photons.

The whole key to this is conservation of energy. Think of friction. Just because less current is flowing doesn't mean energy is lost. It just converts itself to another form. Remember, voltage is the rate of change for the electric fields strength and can be related to work. Electrons accelerate in electric fields so high voltages will drive electrons to accelerate to higher speeds and thus will have more kinetic energy to transfer as they drift through a medium. I hope this helps. Your approach isn't completely wrong but it doesn't consider the underlying mechanics of the forces involved.

Directly addressing your explorations, yes high resistance will leave less current to flow, but in the material itself more kinetic energy is transfered within the medium itself as electrons drift.

Anonymous

Anonymous Fri 08 Oct 2021 18:50:23 No.13729787 Report

Quoted By: >>13729824 >>13729860

I didn't want to sound too stupid since I'm just a lurker, but can OP's question be related to something like taking a bunch of small steps vs taking giant lunges but going the same speed? Or a low torque high revving car vs a high torque low revving car that is the same weight going the same speed? I don't know a single thing about anything electrical. I just want to see if I understand at all what OP is trying to ask.

Anonymous

Anonymous Fri 08 Oct 2021 19:04:33 No.13729824 Report

Quoted By: >>13730328

>>13729787
Yes, your intuition is correct. Power for an engine and light bulb can both be expressed in terms of watts. Its like how efficient an engine uses energy vs how much is distributed as heat. If you run your engine way too fast and hot, it will warp the components. If you run your current to hot, it will warp your element (think of fuses).

Anonymous

Anonymous Fri 08 Oct 2021 19:15:36 No.13729860 Report

Quoted By: >>13729866 >>13730328

>>13729787
Pretty much exactly what you said.
$P=I^2*R$
You'd read this as power equals current squared times resistance. OP was wondering how come the power becomes zero when the resistance becomes zero, because he doesn't have the intuition yet.

>>13728923
If you want to maximize the power, you use the maximum power transfer theorem:
$P_max=\frac{1}{4}*\frac{V^2}{R}$

Anonymous

Anonymous Fri 08 Oct 2021 19:16:43 No.13729866 Report

Quoted By:

>>13729860
that was supposed to be $P_{max}$ , not $P_max$

Anonymous

Anonymous Fri 08 Oct 2021 22:05:08 No.13730328 Report

Quoted By:

>>13729824
>>13729860
Okay, cool, thanks

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