# What is the speed of electric current?

## Recommended Posts

I remember been taught at school that the electricity is a movement of electrons. Ok, it's nice and clear. But then I found out that the speed with which electrons are moving in a wire is millimiters per second. It doesn't make sense to me. So what is electricity if it's not a movement of electrons and what is the speed of it?

##### Share on other sites

45 minutes ago, Morto said:

the speed with which electrons are moving in a wire is millimiters per second. It doesn't make sense to me. So what is electricity if it's not a movement of electrons and what is the speed of it?

Electrons have a lot of charge. It doesn't take much motion for them to create a moderate amount of current. I believe the signal about the motion travels through the electromagnetic field surrounding the wires at the speed of light.

Edited by Lorentz Jr
##### Share on other sites

42 minutes ago, Morto said:

I remember been taught at school that the electricity is a movement of electrons. Ok, it's nice and clear. But then I found out that the speed with which electrons are moving in a wire is millimiters per second. It doesn't make sense to me. So what is electricity if it's not a movement of electrons and what is the speed of it?

Think of a long railway train. A locomotive starts to pull one end. The far end starts moving almost instantly, even though the speed of the train is very slow.

So a signal can be  transmitted very fast, even though the medium transmitting it moves slowly.

##### Share on other sites

as the others mentioned there is a distinction between flow of electrons and flow of charge. As you noticed flow of electrons is extremely slow however flow of charge is near c.

##### Share on other sites

37 minutes ago, Mordred said:

as the others mentioned there is a distinction between flow of electrons and flow of charge.

There's a distinction between flow of electrons and propagation of electromagnetic fields.

Quote

As you noticed flow of electrons is extremely slow however flow of charge is near c.

Propagation of electromagnetic fields is at or near c. There's no distinction between flow of electrons and flow of charge (except for the multiplicative factor of e).

EDIT: As Mordred mentions below, the multiplicative factor should be -e instead of +e.

Edited by Lorentz Jr
##### Share on other sites

12 minutes ago, Lorentz Jr said:

There's a distinction between flow of electrons and propagation of electromagnetic fields.

Propagation of electromagnetic fields is at or near c. There's no distinction between flow of electrons and flow of charge (except for the multiplicative factor of e).

yes you are correct I specified for of charge as that's the lanquage used in a lot of high school lessons. A lot of the high school physics textbooks also apply the flow of charge terminology and subsequently some of their exam questions will trip a student up if they don't realize the question applies flow of charge vs flow of electrons. ( there is one specific lightning question on flow direction for a specific charge that students will get wrong if they don't pay attention to the flow of charge specifically).

lol at least in Canada flow of charge in high school is still taught today, as I often help volunteer as an assistant instructor to high school and undergraduate students

Edited by Mordred
##### Share on other sites

10 minutes ago, Mordred said:

I often help volunteer as an assistant instructor to high school and undergraduate students

Please don't tell them charge flows at near the speed of light in ordinary circuits. That doesn't happen.

##### Share on other sites

7 hours ago, Lorentz Jr said:

Electrons have a lot of charge.

Electrons have the smallest nonzero amount of charge anything can have.

There are a relatively large number of them available to move, so even at a few mm/sec, you can get an appreciable current.

##### Share on other sites

1 minute ago, Lorentz Jr said:

Please don't tell them charge flows at near the speed of light in ordinary circuits. That doesn't happen.

I'm prepared to hear your argument why do you feel the flow of charge doesn't have a rate of c ?

##### Share on other sites

16 minutes ago, swansont said:

Electrons have the smallest nonzero amount of charge anything can have.

Per unit mass, swansont. I know electrons are small. 🙄

15 minutes ago, Mordred said:

I'm prepared to hear your argument why do you feel the flow of charge doesn't have a rate of c ?

Charge is carried by electrons, and typical electron "flow rates" (i.e. drift speeds) are millimeters per second, as mentioned earlier. Feel free to explain your argument why you feel the flow of charge has a rate of c.

Edited by Lorentz Jr
##### Share on other sites

12 minutes ago, Lorentz Jr said:

Per unit mass, swansont. I know electrons are small. 🙄

Charge is carried by electrons, and electrons flow at a rate of millimeters per second, as mentioned earlier. Feel free to explain your argument why you feel the flow of charge has a rate of c.

charge isn't carried by only electrons with flow of charge you are describing the effective average of each individual atom in a conductor. The photons are the mediator of charge  in interparticle interactions. In this case specifically atom to atom. This is effectively the same as your EM field descriptive. With flow of charge you are not specifying the flow of a specific particle but the flow of the effective charge at a given locale

Edited by Mordred
##### Share on other sites

Just now, Mordred said:

The photons are the mediator of charge  in interparticle interactions.

Photons mediate electromagnetic interactions between charges, not "charge in interparticle interactions".

##### Share on other sites

Sure we can focus if you like on language. Either way the flow of charge is a useful descriptive and it is part of the high school curriculum

##### Share on other sites

12 minutes ago, Mordred said:

Sure we can focus if you like on language.

Please don't misrepresent my comments, Mordred. It's extremely rude. I wasn't focusing on language, unless you literally don't know the difference between charge and electromagnetic fields.

Edited by Lorentz Jr
##### Share on other sites

my apologies but did you not correct how I verbally described the above ?

##### Share on other sites

3 minutes ago, Mordred said:

my apologies but did you not correct how I verbally described the above ?

I corrected what you said, but I don't know whether you said the right thing incorrectly (verbal) or you said the wrong thing correctly (substantive). That would depend on what you thought you were saying.

Anyway, I would just ask that you be a little more careful in the future, Mordred. Thanks for chatting.

##### Share on other sites

ok no offense taken and I had no intention of giving offense so My apologies on that by the way I dont feel you deserve that neg rep point so I'm going to remove it.

Edited by Mordred
##### Share on other sites

1 minute ago, Mordred said:

ok no offense taken and I had no intention of giving offense so My apologies on that

##### Share on other sites

I got rid of that neg rep you got above you didn't deserve it there even though rep is a trivial thing

##### Share on other sites

2 minutes ago, Mordred said:

I got rid of that neg rep

Just for the record, I can't imagine many things that are dumber than making science discussions a popularity contest. 🙄

##### Share on other sites

3 minutes ago, Lorentz Jr said:

Just for the record, I can't imagine many things that are dumber than making science discussions a popularity contest. 🙄

on that I fully agree with you, I enjoy a good scientific discussion its natural and part of the scientific process to examine different view points for validity etc. A good discussion should include alternate views for examination

Edited by Mordred
##### Share on other sites

1 hour ago, Lorentz Jr said:

just for the record, I can't imagine many things that are dumber than making science discussions a popularity contest.

Rep points are helpful for people visiting the forum how don't have a very good science background.  It makes it easier for them to understand which people generally post real science content and the individuals who are ignorant of science and just spouting garbage.

##### Share on other sites

23 minutes ago, Bufofrog said:

Rep points ... makes it easier for them to understand which people generally post real science content and the individuals who are ignorant of science and just spouting garbage.

Well, I usually post real physics, and I manage to maintain a low rating through sheer obstinacy, so apparently the system still has a few kinks in it! 😁

##### Share on other sites

2 hours ago, Lorentz Jr said:

Per unit mass, swansont. I know electrons are small. 🙄

The issue is whether Morto knows it. I don’t think they can read your mind, and we can only go by what you write.

##### Share on other sites

4 hours ago, Lorentz Jr said:

Charge is carried by electrons

It can also be 'carried' by holes, the absence of electrons.
How fast do they 'travel' ?

Changes in the field propagate at c , but the limiting factor is how fast you can move the electron.
Semantics or Physics ?

## Create an account

Register a new account