Confusion about conventional current and electron flow and how it runs through and powers a circuit

Question

My apologies if these questions have already been asked and answered, if it has then I haven't found the thread so please link me to it if it exists.

I've just started learning about electricity as I've just recently started to learn electronic engineering online. Right off the bat I'm hit with confusion. I understand that conventional current is that positive charge runs from the positive end of the battery to the negative and that electron flow runs from the negative end of the battery to the positive, both of which via a conductor such as a copper wire.

A) Am I correct that both flows happen simultaneously?

B) If I place components on the circuit, say a resistor close to the positive end of the battery followed by an LED, e.g.

^{simulate this circuit – Schematic created using CircuitLab}

and if I switch the place of the resistor to be on the other side of the circuit, e.g.

^{simulate this circuit}

do both of these work? If so, how?

In my mind I rationalise that surely electricity can only work by travelling in one direction, linearly through a path, but apparently it happens in both directions? How then do you construct a circuit if your power is coming from both directions? In my first schematic above shouldn't the LED burn out due to the electron flow not passing through a resistor first?

C) Do both positive and negative charges' power provide equal amounts of power to a component?

and finally, D) if current runs from both directions out of the battery then does it matter which direction the battery is facing? Could I just flip it around without any consequences?

I hope my beginner level questions don't frustrate people. I've just been trying to rack my brain around this over the last few days. I unfortunately do not have a teacher to ask these questions to.

Any help would be greatly appreciated.

Answer 1

Have you ever played this puzzle? There are fifteen sliding pieces, numbered 1 to 15, arranged in a 4x4 grid. It has one "hole" where there is no piece. You can move any piece adjacent to the hole into that space.

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As you play the game, what is moving: the numbered pieces, or the hole?

Technically speaking, you are moving the numbered pieces. They are the electrons, the physical objects that move around. You can even get them to move in a closed path (a circuit).

But if you have played this game for enough time, you quickly realize how important the hole is to the strategy of the game. A skilled player can move the hole anywhere he wants, and the hole can even move around in a closed circuit. The hole represents the absence of electrons, and can move around just as the electrons themselves can. In semiconductor theory, we even officially call them "holes" and treat them like a particle, even if they're not.

Whichever way you count, there is something moving. We call this moving thing "charge". Benjamin Franklin (as quoted below) called it "electrical fire".

Notice that whatever move you make, there are always 15 numbered pieces and 1 hole. We say that this is conservation of charge, and was discovered by Franklin in the quote below. As long as we are counting or adding things, it makes sense to make one kind of charge positive and another kind negative. How shall we assign which is which?

The problem is that there has never been -- and never will be -- a device which can see electrons or holes. They're just too small and too fast. So Franklin arbitrarily assigned them:

We suppose as aforesaid, That Electrical Fire is a common Element, of which every one of the three Persons abovementioned has his equal Share before any Operation is begun with the Tube. A who stands on Wax, and rubs the Tube, collects the Electrical Fire from himself into the Glass; and his Communication with the common Stock being cut off by the Wax, his Body is not again immediately supply’d. B, who stands upon Wax likewise, passing his Knuckle along near the Tube, receives the Fire which was collected by the Glass from A; and his Communication with the common Stock being likewise cutt off, he retains the additional Quantity received. to C, standing on the Floor, both appear to be electrised; for he having only the middle Quantity of Electrical Fire receives a Spark on approaching B, who has an over-quantity, but gives one to A, who has an under-quantity.

If A and B touch each other, the Spark between them is stronger, because the Difference between them is greater. After such Touch, there is no Spark between either of them and C; because the Electrical Fire in all is reduced to the original Equality. If they touch while Electrising, the Equality is never destroyed, the Fire only circulating.

Hence have arisen some new Terms among us. We say B (and other Bodies alike circumstanced) are electrised positively; A negatively: Or rather B is electrised plus and A minus. And we daily in our Experiments electrise Bodies plus or minus as we think proper. These Terms we may use till your Philosophers give us better.

Benjamin Franklin, Letter to Peter Collinson, May 25, 1747. Emphasis added.

Franklin wrote this letter to Peter Collinson, an English naturalist. Franklin was somewhat right about "These Terms we may use till your Philosophers give us better." Indeed, it was an Englishman (physicist J. J. Thomson) who discovered that the actual particles moving in a circuit -- which he called "electrons" -- are negatively-charged. Unfortunately, the connotation of positive and negative stuck.

Answer 2

I understand that conventional current is that positive charge runs from [positive to negative] and that electron flow runs from [negative to positive]

A) Am I correct that both flows happen simultaneously?

There is only one flow; the electrons move. Benjamin Franklin picked a convention that happened to be the opposite of the "real" action, because he didn't know about electrons. That convention got established before electrons were well-understood. Because of that convention, we now say that electrons have negative charge. We use that convention even though it's not representative of the physical activity. Forget entirely about electron flow unless you're trying to invent transistors; always think in conventional flow terms.

B) If I switch the place of the resistor to be on the other side of the circuit...

The position of the resistor doesn't change the direction of conventional flow, so the diode, now reversed, is now blocking any current flow. It doesn't matter which side of the diode the resistor is on for your circuit.

C) Do both positive and negative charges' power provide equal amounts of power to a component?

There's only one flow.

D) if current runs from both directions out of the battery then does it matter which direction the battery is facing?

Current doesn't run out of both directions. By convention, current flows out of the positive terminal and returns to the negative. The facing of the battery absolutely matters.

Answer 3

A) Am I correct that both flows happen simultaneously?

There is one flow and both of these are ways of describing it.

Only electrons are real. However, all of the equations still work if you consider it as a flow of "anti-electrons" going the other way. Due to an accident of history, that is the way around that we describe it. But usually we don't talk about electrons or "anti-electrons" at all, we just talk about current.

B) If I place components on the circuit, say a resistor close to the positive end of the battery followed by an LED, e.g.

and if I switch the place of the resistor to be on the other side of the circuit, e.g.

do both of these work?

Yes. Not quite, the diode is backwards in the second one.

If so, how?

When you have a turbine in a water pipe, and you stick a basketball in the pipe to slow down the water, does it matter which side of the turbine you put the ball on?

C) Do both positive and negative charges' power provide equal amounts of power to a component?

There is only one flow, and that flow provides power to the component. Whether you say it's a flow of negative charge, or positive charge in the opposite direction doesn't matter since the math works out either way.

D) if current runs from both directions out of the battery then does it matter which direction the battery is facing? Could I just flip it around without any consequences?

No, because the flow will be in the wrong direction.

Answer 4

The only charge carriers in wires are negative, and are called electrons. But is this really true? There are two asterisks regarding this:

While electrons might do the only 'flowing' in a wire, since a positron, the positive counterpart to an electron, does not exist (unless you form a positron-electron pair with quantum physics, but that is a whole other story), in electro-chemistry, positive ions can also carry charge and result in current. These atoms or molecules have more protons than they have electrons, and thus have a positive charge. Hence, yes, we can have both a component to the current where positive charge carriers flow from positive to negative, and negative charge carriers flow from negative to positive. (but this does not occur in metal wires)

The second asterisk is when we look at electrons and holes. When materials form a crystal structure, the atom is not (as) able to freely move around through the material. If one of its electrons now starts flowing due to current, this leaves behind an 'absence' of an electron. This 'absence' is like a positive charge carrier, and as electrons jump from atom to atom, it can behave like a positive charge carrier. We usually call this a hole, and we can actually see that it behaves very much like a particle with a effective mass and drift velocity. These holes also behave differently under a magnetic field, and is the reason why some materials can have a positive hall coefficient.

I will not answer the individual additional questions in your question, since others here have done a better job of that than I can.

Answer 5

I've just started learning about electricity as I've just recently started to learn electronic engineering online. Right off the bat I'm hit with confusion. I understand that conventional current is that positive charge runs from the positive end of the battery to the negative and that electron flow runs from the negative end of the battery to the positive, both of which via a conductor such as a copper wire.

First thing to note is that in the way they're initially introduced in a textbook, these effectively represent two different ways of looking at the same thing. IIRC, conventional flow has it's name because intuitively we just assumed that it would be a "positive" or "noninverted" charge making electricity work. Eventually we found out that it's electrons that actually travel around a circuit. An electron is an electron, and an absence of one is referred to as a hole. Especially as you're starting to learn, it's probably best to work with electron flow and remember that conventional flow diagrams exist, just in case you run into one. Edit: In electrical(electrician, not ee) school I was taught that conventional flow is obsolete and should be phased out. I've since found out that both are still widely used, with textbooks being printed in both.

That said, there is an apparent fundamental difference in mobility between N and P type semiconductors. I'm not well informed about this, but as I understand it, the reason P mosfets are slower(have higher gate capacitance) than N ones has to do with holes being used as a carrier and having less electron (or hole) mobility.

A) Am I correct that both flows happen simultaneously?

Yes. These are just two different ways of looking at the same thing. Electrons are the only thing moving around, and places that are absent electrons are holes.

B) If I place components on the circuit, say a resistor close to the positive end of the battery followed by an LED, e.g. and if I switch the place of the resistor to be on the other side of the circuit, e.g. do both of these work? If so, how?

Changing the order of a series arrangement like this as you have won't have an effect on the circuit because the same current flows through both the resistor and the LED. I didn't initially notice that you'd also changed the direction of the diode, which will change the direction in which it resists current flow.

In my mind I rationalise that surely electricity can only work by travelling in one direction, linearly through a path, but apparently it happens in both directions?

For current to exist, electrons must be moving in a single direction, and they flow from high voltage to lower voltage. But sometimes, for most power transition for instance, the direction of pressure and current is alternated, and this is what is referred to as AC current. One simplification I find helps most people is to think of the electrons as a fluid and the conductors they travel through as pipes and devices.

How then do you construct a circuit if your power is coming from both directions?

Sometimes you want AC specifically rather than DC. There are far too many ways and reasons to take advantage of AC or DC electrical systems to mention here.

In my first schematic above shouldn't the LED burn out due to the electron flow not passing through a resistor first?

No, the same current flows through devices in series. Now for the obligatory textbook mentions. If you read up on Voltage, Current, Ohm's law, Watt's Law, Series and parallel resistance, Kirchoff's law, you'll get a good start on understanding simple circuits.

C) Do both positive and negative charges' power provide equal amounts of power to a component?

P=IE, which is to say power is equal to voltage drop multiplied by current, in a purely resistive circuit (inductance and capacitance complicate this a bit, creating reactive power, which is stored and put back into the circuit). Some devices, such as diodes will only allow current to pass through them one way. and many devices cannot operate if voltage is reversed, but all other things being equal, the same current passing over the same resistance will use the same amount of power.

D) if current runs from both directions out of the battery then does it matter which direction the battery is facing? Could I just flip it around without any consequences?

No, directionality has been discussed, but to be clear many devices will malfunction or be destroyed if DC is connected to them backward, while other devices can be designed to be extremely tolerant. AC on the other hand alternates at ~50-60Hz, so most AC devices function just fine when connected backwards, however polarized plugs exist in order to protect some AC devices from reverse connection.

I hope my beginner level questions don't frustrate people. I've just been trying to rack my brain around this over the last few days. I unfortunately do not have a teacher to ask these questions to.

No worries, I think a lot of these get removed for being too broad or lacking research. I think in this case you probably just need an idea of where to start reading. Fair warning, you can't skip a lot of steps in learning about this stuff and it can be hard to know what to learn next. You can do a lot of hobby stuff without going so far as using calculus, but expect to regularly use basic algebra.