Voltage and current in a resistor

AI Thread Summary
Voltage represents the potential energy due to an imbalance of charges, while current is the flow of those charges. In a resistor, the resistance does not draw current but instead impedes it, resulting in a voltage drop across the resistor proportional to its resistance, as described by Ohm's Law (V=IR). The term "voltage drop" refers to the energy lost as current flows through the resistor, which dissipates electrical energy. Understanding voltage as a measurable quantity involves recognizing it as the work done per unit charge, quantified in joules per coulomb. The discussion emphasizes the importance of grasping these fundamental concepts in electrical engineering for a deeper understanding of circuit behavior.
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So I know that voltage is a sort of pressure due to an imbalance of charges. And current is the resulting flow of charges. So when it comes to a resistor, does the resistance draw a current from the curcuit as well as a voltage? And what is meant by "voltage drop" across a resistor/element. Please use analogies in your answers please and thanks.
 
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Voltage is a potential. ie biggest dude ever stands in front of you. If you don't make him mad no harm no foul (lets call him 480v). He could potentially kick your butt, but he probably won't. Now if you make him mad and he takes a swing at you (better run this guy can punch a few amps), misses and hits air, same thing, no harm no foul, he looks like a douche, we all go home. But if your face happens to be there, bang welcome to resistance. So you're a 100 ohms and buddy hits you with 4.8 amps, and your still standing, like a trooper. All of a sudden buddy decides to round house you and you and your friend is standing by your side, You get hit, and your friend gets hit. You're still 100 ohms but, your friend happens to be a big fat guy so he's got like 200 ohms of resistance, So instead of you feeling the full brunt of potential, you only get 1/3 and your friend has 320 Volts dropped on him. However, the remaining 160V and 4.8 amps was enough to drop you to the ground, and buddy, seeings how you made him so mad decides to stomp your face. So you are lying parallel to the concrete, your face at 100 ohms the concrete at 100. He lays his boot down and 'whack' you're out cold 480V on your face, 2.4 amps to you and 480V and 2.4 amps to the concrete. And you know what, buddy's toe hurts, cause Power in= Power out.
 
I don't quite understand the last part with the concrete. But lol on the analogy, thanks for that btw... So what I'm struggling with is this: voltage is potential, if the potential finds a pathway to start actualizing the potential (conductors), then it throws out current, and if someone's face (resistance) is in the way then depending on how fat the face is, a higher voltage will be dropped on/across it? But less current?

And what's meant by drop of current across a load anyway. Is that how much of the total potential (from the source) the element "eats up" from the total potential?
 
What exactly are you studying right now. AC/ DC I could be broad, but it would help me narrow the field a little.
 
For general terms V=IR
 
mohammad_adam said:
So I know that voltage is a sort of pressure due to an imbalance of charges. And current is the resulting flow of charges. So when it comes to a resistor, does the resistance draw a current from the curcuit as well as a voltage? And what is meant by "voltage drop" across a resistor/element. Please use analogies in your answers please and thanks.
Do you know how to use wikipedia?
 
In my 4th year of electrical engineering. Just never really thought of these concepts fundamentally. I know how to use Wikipedia lol thanks for asking but I thought the point of this forum was to be able to talk on a more personal level with ppl who know these concepts in and out so that I don't just end up with half-baked knowledge about things and end up just rolling with the terms and equations of things I don't really truly understand (like far too many ppl do, at least at my university)
 
mohammad_adam said:
In my 4th year of electrical engineering. Just never really thought of these concepts fundamentally.
In that case it is very strange you didn't think of Ohm's law before. Resistor is a passive element and doesn't add energy to the circuit. Hence the "voltage drop" expression.
 
Right so what exactly is the "drop"? Because a source (dc in this example) is providing steady voltage so it's not like the "drop across" the resistor is a chunk of that voltage being expended over the resistor. So what is it then?? Sorry if I'm not articulating myself well enough. I just don't understand the expression and how it ties into the whole big pic
 
  • #10
If you connect a 6 Ω resistor across a 12 volt battery, 2A of current flows, and all the 12 V is dropped across that resistor. If you were to replace the 6 Ω by a 4 Ω and a 2 Ω in series, then again a 2A current will flow. Now, the voltage drop across the 4 Ω resistor will be 8 V, in accordance with Ohm's Law.
 
  • #11
I fully agree. But what does it exactly mean that 8v is dropped across the 4 ohm and 4v "dropped across" the 2 ohm?
 
  • #12
Maybe it's a language thing that's messing me up ?
 
  • #13
You could say 8 V is lost across the resistor, or that 8 V appears across it, or that 8 V can be measured across it. "Dropped" has connotations of energy loss, as opposed to energy gain.
 
  • #14
I guess it makes sense. The resistor, depending on its resistance takes the amount of voltage it needs out of the tub of voltage supplied and has it "dropped" across itself in accordance with ohms law. I know I sound like a 5th grade retard here so bear with me lol and thanks for doing so. So with that somewhat settled... My next question is: how is voltage a measurable quantity? I mean I know that booking a voltmeter across two terminals produces a reading, but what how is the electric "pressure" actually being determined and quantified?
 
  • #15
I know that a volt is a joule/coulomb so the amount of work done by a unit of charge.. Which is a coulomb?? Also I have never understood the coulomb. And read a lot in attempts to understand it but I just get more confused. How is charge quantifiable. This blows my mind. Isn't it just essentially "stuff"?
 
  • #16
You don't drop current but you do draw it.
Your house has a 100 amp service
That means at any given time a hundred amps can be supplied.
To actually visualize stop thinking of things as resistance and start thinking of them as a load.
A microwave needs 1200W of power to nuke your pizza pop.
That means it is going to draw 10 amps of current at 120v.
Inside the microwave 5 volts are allocated to run the clock (your voltage drop) the other 115V are used to microwave the pizza pop, current is equal through both.
And by golly if you are a forth year engineer I need to go back to school or run for the hills.
 
  • #17
Oh dude, your going back to flux, flux sucks
 
  • #18
mohammad_adam said:
I know that a volt is a joule/coulomb so the amount of work done by a unit of charge.. Which is a coulomb?? Also I have never understood the coulomb. And read a lot in attempts to understand it but I just get more confused. How is charge quantifiable. This blows my mind. Isn't it just essentially "stuff"?
A coulomb is just a bunch of electrons (or protons), quite a lot really. You can't get any charge less than 1 electron; that makes it the basic unit of charge (hand in hand with the positron and the proton).
 
  • #19
I don't remember saying that current was dropped. I've been meaning to figure out how "voltage is dropped across a load/resistance". And isn't saying that a load "draws" current misleading? Because I would picture the load as just being there while current is passed through it. And based on its atomic makeup or whatever, it impedes the flow of electrons thereby limiting the amount of current being forced through it.
With regards to the voltage I found this (which may help u understand what I was asking in the first place):
(Someone answering a similar question on the net)

Larger resistors have larger voltage drops. Why? Before we can answer that we must better understand what exactly a resistor does.

A resistor resists the flow of current. This resistance means that some work must be done to "push" current through the resistor. Whenever work is done on charge, we have voltage. Thus, when current flows through a resistor, there is some voltage across the resistor.

The larger the resistance, the more work required to "push" the current through the resistor, the more work done the larger the voltage drop across said resistor.

End quote

So as I see it (and please correct me if I'm wrong, that's the whole point here), voltage from a battery is more like a bottled up force (from an imbalance of charges wanting to balance themselves out) and then once that force is allowed a pathway, it causes electrons to flow in the whole circuit due to a sort of chain reaction, and then when that chain reaction (current) is slowed by an impedance to that current, the atoms in the resistor do work on the charges to resist that flow thereby causing another voltage/pressure of its own that can be measured...?

Btw this whol time I've just been picturing a simple series circuit supplied by a dc source.

As for a coulomb being a bunch of electrons... It's not just a bunch of electrons in the way that avagadros number is a bunch of molecules/mol correct? Because avagadros number is just a way to simplify numbers... But a coulomb is not just a number of things it's actually "something" about those things/electrons which is being captured. What is that thing (I know ur going to say it's charge) and how on Earth is it being captured?
Maybe I should just go to bed lol

zzzzzzzzZZZZZZZZZZZZZZ
 
  • #20
As for a coulomb being a bunch of electrons... It's not just a bunch of electrons in the way that avagadros number is a bunch of molecules
Yes, just a large count of electrons. You could have them all grouped together, or count them one at a time as they pass by.
 
  • #21
Yeah but a coulomb is the CHARGE of so many electrons. Not just a number of so many electrons. So u haven't really answered my question. Or in going insane. Don't know which one of the two
 
  • #22
Yes, a count of electronic charge.
 
  • #23
Lol ur not helping me man!
 
  • #24
"A resistor resists the flow of current."
This is where the historical choice of the word "resistor" tends to mess up the understanding of what goes on. The Mechanical Analogy can colour ones appreciation of Electrical Energy Flow and can lead to 'inappropriate' conclusions, I think. A resistor doesn't 'resist' the flow of current any more than a motor, an antenna or a 50W amplifier (i.e. any other load) in a circuit. When a charge passes along any non-ideal conduction path, Energy will be transferred (i.e. away from the circuit).
Rather than talking about a 'force' against another 'force' just think of a resistor being an element that dissipates electrical energy as charges flow around a circuit. Each of the circuit elements will dissipate their share of energy.
V=IR tells you the energy loss per coulomb and all the V's must add up to the V of the power supply (K2: aka Energy Conservation). I always reckon that, once you have stated a Scientific situation with the appropriate Maths, that is probably the best way of expressing it. Arm waving about the same phenomenon is not very often a better approach. Maths is just an alternative to the spoken language and you shouldn't attribute anything magical to the use of 'words' to explain something - except for the familiarity in some cases. The solution is to get used to using Maths for such situations.
 
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  • #25
I see. Thx for ur reply.
 
  • #26
I feel so lost when it comes to trying to understand the fundamentals. I have a hard time just running with things from an overview perspective. And then the more I inquire about the fundamentals the more confused I get. It's rather disheartening. End rant. I'll eat some ice cream and I'll be fine. Thx guys. And didn't mean to be rude to the person that suggested Wikipedia. Cheers.
 
  • #27
mohammad_adam said:
I see. Thx for ur reply.

It would be appreciated, on PF, if you could use 'proper' words in your contributions. Firstly, it is a matter of courtesy and secondly, in a technical subject, non-word abbreviations are used in a technical context. "ur" can mean many things; "your" means only one thing.
 
  • #28
I shall keep it mind for next time. Thanks.
 
  • #29
mohammad_adam said:
I feel so lost when it comes to trying to understand the fundamentals.
You have all our sympathy in this. The way to deal with that problem has to be to stick with it and to start at the beginning. Many people try to run before they can walk. Doing simple example exercises can be a massive help - like doing scales every day when learning the piano. Things can become much easier when you are really familiar with the initial numerical relationships. boring boring, I know but it will produce results.
 
  • #30
mohammad_adam said:
Yeah but a coulomb is the CHARGE of so many electrons. Not just a number of so many electrons. So u haven't really answered my question. Or in going insane. Don't know which one of the two
The concept of 'charge' came along long before anyone was aware of electrons. There is absolutely no need to think 'particles' in most of everyday Electricity problems. Think of it a s 'something' that flows and has certain properties and that can be measured by some means. I suggest the reason that you are struggling with is could simply be lack of familiarity. The same question ("what is?") can be asked about all the quantities we deal with (mass, time etc). It's all very abstract, when you delve deeply into it.
 
  • #31
Yes I totally agree. It's a shame that in universities things are taught at such high pace with such heavy course loads that students rarely get time to ponder these things in great detail. I plan to make it a sort of hobby to dig deep into the basics. I know it's not necessary for engineering purposes but interesting nonetheless.
 
  • #32
My point is that the basics that you learn for Engineering will help you with in-depth 'understanding', if you get those basics as second nature. The two levels are in agreement with each other, remember - so one can help the other.
 
  • #33
The semantics in this thread is confusing. Instead of talking "voltage" everywhere, let's talk about electric potential (V) (measured in volts or joules per coulomb) and potential difference (deltaV).
For a current to flow from point A to point B, there must be a potentil difference between the 2 points and a pathway for the chargs to flow. The pathway could be a light bulb and wires connected between A and B
Although I hate to do it, let's talk about the flow of positive charge in the following example:
Let's say the potentail at A is +20V and the potential at B is 0V. (This means that point B could be grounded). Hence the potential difference (deltaV) between the points A and B is -20V.
If 1 coulomb of (+) charge (Q) flows from A to B, the energy dissipated (deltaE) by the charge will be 20 joules.
{deltaE= QxdeltaV}
The light bulb will release most of this energy as heat because of its resistance, BUT the connecting wires also have a little resistance, so they will each dissipate a small amount of heat energy as well.
So, between A and B, we have wire1...lamp...wire2.
Yoiur voltmeter might show the following maesurements: across the ends of wire1, 0.1 volt, across the lamp,19.7 volts.and across wire2, 0.2 volt.
As an exercise, if the current flow through the circuit is 2 amperes, calculate the reistance of each of the parts of the circuit using Ohms Law.
 
  • #34
daqddyo1 said:
The semantics in this thread is confusing. Instead of talking "voltage" everywhere, let's talk about electric potential (V) (measured in volts or joules per coulomb) and potential difference (deltaV).
For a current to flow from point A to point B, there must be a potentil difference between the 2 points and a pathway for the chargs to flow. The pathway could be a light bulb and wires connected between A and B
Although I hate to do it, let's talk about the flow of positive charge in the following example:
Let's say the potentail at A is +20V and the potential at B is 0V. (This means that point B could be grounded). Hence the potential difference (deltaV) between the points A and B is -20V.
If 1 coulomb of (+) charge (Q) flows from A to B, the energy dissipated (deltaE) by the charge will be 20 joules.
{deltaE= QxdeltaV}
The light bulb will release most of this energy as heat because of its resistance, BUT the connecting wires also have a little resistance, so they will each dissipate a small amount of heat energy as well.
So, between A and B, we have wire1...lamp...wire2.
Yoiur voltmeter might show the following maesurements: across the ends of wire1, 0.1 volt, across the lamp,19.7 volts.and across wire2, 0.2 volt.
As an exercise, if the current flow through the circuit is 2 amperes, calculate the reistance of each of the parts of the circuit using Ohms Law.

Why do you hate to do it? The rest of what you write is absolutely fine. Who cares about the charge of the particles that happen to carry the charge? ("A minus times a minus is a plus", is well enough known by anyone who is even tinkering with EE). We are talking Classical Electricity here, which was developed way before anyone came across the electron. Imo, it's when people (like you), who are clearly OK with the subject, start to make some sort of distinction between conventional current and where electrons go, that the less well informed start to get uncomfortable. You really should not 'admit' / suggest that there's any real confusion between the two approaches; it only makes things worse.
 
  • #35
mohammad_adam said:
Lol ur not helping me man!
Besides what sophiecentaur said, the use of "text-speak" isn't permitted here at PF.
From the rules (https://www.physicsforums.com/threads/physics-forums-global-guidelines.414380/):
Language:
All posts must be in English. Posts in other languages will be deleted. Pay reasonable attention to written English communication standards. This includes the use of proper grammatical structure, punctuation, capitalization, spacing, and spelling. In particular, "I" is capitalized, there's a space after (but not before) a comma, a period, and other punctuation. Multiple exclamation marks are also discouraged. SMS messaging shorthand ("text-message-speak"), such as using "u" for "you", "please" for "please", or "wanna" for "want to" is not acceptable.
 
  • #36
mohammad_adam said:
Yes I totally agree. It's a shame that in universities things are taught at such high pace with such heavy course loads that students rarely get time to ponder these things in great detail. I plan to make it a sort of hobby to dig deep into the basics. I know it's not necessary for engineering purposes but interesting nonetheless.
I would hope so (that you dig deeper into the basics), especially for someone in the fourth year of an EE degree program. Very basic concepts such as the drop in potential (voltage drop) across a resistor are presented early on in electronics, and really aren't very complicated. A voltmeter placed on either side of a resister can be used to measure the difference in potential.
 
  • #37
I think people are confusing my ability to use a voltmeter with my ability to understand the inner workings of "voltage" itself. I'm totally okay with circuit analyses and ohms law and connecting two leads into a voltmeter (in parallel if my memory serves me right - I have done it a few hundred times). Just having troubles visualizing it all, if that's even possible in the first place.

But like sophiecentaur said:

"The concept of 'charge' came along long before anyone was aware of electrons. There is absolutely no need to think 'particles' in most of everyday Electricity problems. Think of it a s 'something' that flows and has certain properties and that can be measured by some means. I suggest the reason that you are struggling with is could simply be lack of familiarity. The same question ("what is?") can be asked about all the quantities we deal with (mass, time etc). It's all very abstract, when you delve deeply into it."

Perhaps I'm delving too deeply and should do as suggested and just think of these things as "something that flows and has certain properties".

I guess these concepts (EE ones) just have a weirder approach to them than other things because there's so little that can be visualized and so we rely on measurement tools to observe behavior as opposed to trying to picture what's physically happening. Kind of sucky because my brain likes visualization.

Anyways, thank you everyone for the help/input. I greatly appreciate you guys taking the time to try and help me out.
 
  • #38
I think your problem here may just be because you are thinking of Electricity as something different from other aspects of Science. My opinion is that people find it 'strange', simply because they are less familiar with it. We could have ( and you can read plenty of them on PF) a similar conversation about the more familiar Forces, Energy and Mass and we would come up against a wall at the end, because we can never 'understand' it all.
I am a bit 'snobby' about visualisation (a.k.a. analogies) because it can be used as a tool to draw unjustified conclusions. But, Of course, I / we all use them all the time - but privately.
 
  • #39
Yes I totally 100% agree. My problem is overthinking. And the reason I don't overthink the other aspects of science (the more 'familiar' forces etc that you mentioned) is because they're just there and I take them for granted just because they're considered 'visualizable' and less complicated than electricity (even when they're really not).

I do want to continue delving too deeply in my spare time though just because it's fun. I won't delve too deeply to the point where double slits start showing up and I start pondering my own existence haha. I've started to learn not to fall too far into the rabbits hole. That place is way too complicated and not to be understood by someone like me that's for sure.
 
  • #40
Still wouldn't mind if someone could take a stab at explaining voltage drop as opposed to voltage (from say a battery). Looking for a conceptual understanding, not just terminology and tips on how to measure the drop with a voltmeter.
 
  • #41
Point 1:
Remember, potential at a point (measured in volts) is the electrical potential energy of 1 coulomb of charge at that point. That is why 1 volt is defined as 1 joule of energy per coulomb.
If this charge flows through a circuit to another point and let's say through a lamp, then the charge loses some electrical potential energy. (The lost energy is released in the form of heat and light).
Hence we say that there is a potential difference that can be measured across the lamp terminals. This is loosely referred to as a "voltage drop".
Point 2:
If you want to talk about the "voltage" or potential at the positive terminal of a 1.5 V battery you have to be very careful of the semantics. This is because you are measuring the potential relative to some other point in the universe. But which point?
Let's say we're going to measure its potential relative to the negative teminal of that battery. What is its potential there?
Well, it doesn't matter. What matters is the potential difference between the two battery terminals as measured by a voltmeter. That instrument will read 1.5 V (even if the negative terminal is at -47V and the positive terminal is at -45.5V because of the battery's location in some circuit).
Always be very clear in your own mind what is meant by "voltage" and "voltage drop" or even voltage rise" by remembering that they are loose synonyms for the proper terms (electric potential and electric potential difference).
 
  • #42
mohammad_adam said:
Still wouldn't mind if someone could take a stab at explaining voltage drop as opposed to voltage (from say a battery). Looking for a conceptual understanding, not just terminology and tips on how to measure the drop with a voltmeter.
Voltage drop = energy per unit charge lost.
An emf = energy per unit charge gained.

In a resistor electrons collide with lattice ions and photons are given off whenever an electron drops from conduction to valence. This is why a wire carrying large current feels warm. Electrons here are losing energy since valence band is a lower energy state than conduction band.

In a battery, or generator, electrons gain energy. For a battery, positive & negative ions are moved against the internal E field. In order to move a positive ion towards the positive terminal, work must be done. The chemical reaction known as "redox" (reduction-oxidation) provides this work. We call this gain in energy per unit charge "emf". For the resistor, we call the loss in energy per unit charge "drop", or "voltage drop".

Did I help?

Claude
 
  • #43
Umm-- isn't simpler to just look at the circuit ( loop) from the voltage source - and back. Each of the elements ( wires, resistors, etc) each "drop" some the voltage. The Sum of all of the "drop"s is equal to the source. -- Not the best language, but in power for example, a long extension cord has a higher resistance than a short one, so it "drops" the voltage, and there is less available to the actual load. There is no need to bring charge, emf, columbs, or any other language into this question. V in Volts, R in Ohms, and I in Amps --- draw a circuit, with 3 resistors, and a DC Voltage...
 
  • #44
Windadct said:
Umm-- isn't simpler to just look at the circuit ( loop) from the voltage source - and back. Each of the elements ( wires, resistors, etc) each "drop" some the voltage. The Sum of all of the "drop"s is equal to the source. -- Not the best language, but in power for example, a long extension cord has a higher resistance than a short one, so it "drops" the voltage, and there is less available to the actual load. There is no need to bring charge, emf, columbs, or any other language into this question. V in Volts, R in Ohms, and I in Amps --- draw a circuit, with 3 resistors, and a DC Voltage...
But the OP wanted a more detailed explanation. To start, I would use the circuit theory approach, i.e. Ohm, KVL, KCL. But for a more in depth view, the resistor is a lattice where charges collide with lattice ions and drop to a lower energy state releasing photons (heat). It just depends on how deep of an analysis is being requested. That was what I was thinking when I replied.

Claude
 
  • #45
mohammad_adam said:
Still wouldn't mind if someone could take a stab at explaining voltage drop as opposed to voltage (from say a battery). Looking for a conceptual understanding, not just terminology and tips on how to measure the drop with a voltmeter.
If you want a good analogue, the Potential Difference (Voltage) the Battery is the equivalent to taking (pumping) water to a reservoir at height h. The water makes its way down to the start level, through a series of water wheels, to represent Electrical Loads (forget the pipes, which are wide enough to ignore any friction and for the actual speed of the water to be negligible). The water emerges from the bottom with (notionally) no kinetic energy so the ' vertical drops'(h1, h2, h3 etc.) across each of the water wheels will deliver the same Power as the total Power out of all the water wheels. h will equal h1+h2+h3 +++. Note - this is NOT the classic water model with thick and thin pipes (which is pretty hopeless because it is based on pressure and speeds and not energy).
Gravitational potential (gh) is Joules per kilogram and Electrical Potential is joules per Coulomb

You have to avoid asking the question about how it's all arranged so that the water comes out with no KE; it just ' adjusts itself' for a series of resistors.

Voltage measurement: You just connect the voltmeter across the two points of interest (it is always two points because you are after the potential Difference), either across the battery or across each resistor. The resistor drops will add up to the battery voltage.
 
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  • #46
"voltage drop" to me is Newton's third law...the fundamental concept from physics that should be understood 2 -5 years before Engineering Classes... if he is asking for analogies - then he is not asking about how electrons move, amount of charge ... when you push on something - it pushes back... that is the concept. If you Push electrons though something -- it pushes back. Unless there is some more complex principal you are trying to comprehend - there is no need to discuss anything else.
Even trying to discuss resistance at an atomic level does not work here, because different materials generate "resistance" different ways ... Wire or semiconductor, inductor - electrons vs holes, whatever V= I * R
Sorry to vent a little - I must be missing what the OP is asking -
 
  • #47
Although you are an electric engineering senior, you are asking high-school questions. I don't mean sarcasm, I just want to help. You should buy a proper physics introductory textbook, and then go for the advanced electricity and engineering textbooks, since you may also have a loose foundation in engineering.
You must spend the next 1~2 years of your life self - studying to rebuild a foundation and be a proper engineer.
 
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  • #48
Windadct said:
"voltage drop" to me is Newton's third law....the fundamental concept from physics that should be understood 2 -5 years before Engineering Classes... if he is asking for analogies - then he is not asking about how electrons move, amount of charge ... when you push on something - it pushes back... that is the concept. If you Push electrons though something -- it pushes back. Unless there is some more complex principal you are trying to comprehend - there is no need to discuss anything else.
Even trying to discuss resistance at an atomic level does not work here, because different materials generate "resistance" different ways ... Wire or semiconductor, inductor - electrons vs holes, whatever V= I * R
Sorry to vent a little - I must be missing what the OP is asking -

The analogue for N3 is surely the Back emf as you try to change the current in an inductor. As with the reaction force from a mass when you push it, no Power is necessarily lost. In a component that is dissipating Energy, Power is loss.

There is a value 'R' which is the ratio of PD and Current for all components but it is only constant when you have a linear conductor (metal - Ohm's Law applies). It is risky to use the concept 'R' when dealing with a semiconductor when the VI characteristic is not a straight line. For calculations, you should stick with V and I in any equation you try to form.
 
  • #49
Just dropping in with my own analogy here. Imagine a world where lakes are on islands floating above the ocean. A lake flow into a river, which flow downwards, decreasing the waters potential energy. I we were to put a drain in the middle of a lake, connected directly to the sea below, the water would get there a lot faster. In this analogy, the river is the resistor, impeding the waters wish to get salty.

In these terms, I think of the voltage as the gravitational potential energy stored in the water. As voltage is due to separation of charges, the water goes downwards due to separation from the ocean. As a footnote, the Aral Sea is an open circuit.
 
  • #50
Sophie -not to be contrarian- IMO if the force applied is being equally reacted ( steady state as with drag / friction / resistance ) --- then the F applied = F reaction -- and work is done(power loss) . I agree to the inductor - this is the case where energy is stored in the system - inductors / capacitors... in these cases we are using Impedance - and we are talking about time varying cases - but regardless of the time - the Total force applied (Voltage) at any point in time is equal to the sum of each of the elements "reactive" force. ( really KVL right ?- the total sum =0, although the OP may ONLY see KVL as a mathematical tool - it is a (the) fundamental issue)
Consider a motor - not a resistor - looks like an inductor, then the back emf - is proportional to the mechanical force ( torque) and the power is the EMF ( Volts) * current... if there are resistors capacitors - what ever else in the circuit --- the back EMF becomes one of the SUM of forces - resisting the flow of current ( as I say pushing back).
This is my understanding - I do not consider this an analogy, but the fundamental principal. The same principal can be applied to many ( if not most) classical physical systems. Water in pipes, springs, gravity and friction blocs...
 
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