electrons per AMP ?

Status
Not open for further replies.

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Actually an ampere is a rate. If you had an AC circuit in which one electron passed the same point 6.24 x 10 to the 18th power times in one second while moving back and forth you would have an amp with only one electron.

Asking how many electrons make an amp is like asking how many water molecules make a GPM.
 

rattus

Senior Member
Whoa there Nellie!

Whoa there Nellie!

Amps are something you can count-that is what this post is about. I tell my class to picture amps as tennis balls. Amp is number of electrons (or a group of electrons) moving past a point over a period of time. Amp means nothing without a time frame. 5 amps tells us nothing, 5 amps per hour is a definite rate of flow. Of course in electrical work, we assume "per Hour," whenever you see amp mentally add "per hour" to it. Except in science it would be .0014 amps per second. My brother runs 10 miles per hour, he also runs 240 miles per day.
The multiplying is used when you want to find out power, watts: 5 amps x 120 volts = 600 watts (per hour)

A reading of 5 amps is not meaningless; it tells us that the rate of charge flow is 5 coulombs/sec.

Amps/second is meaningless just like amps/hour.

The watt is the unit of electrical power; it means we are expending energy at the rate of 1 joule/second.

Watts/hour is also meaningless.
 

Mayimbe

Senior Member
Location
Horsham, UK
I dont know why, but what mlnk says makes sense, and what rattus says makes sense too. Its like light wave/particule duality. For some cases you use wave (refraction) and for other you use particule (reflection). In this case, for some cases you use Amps per hour (physical view), and for others just Amps (engineer view).
 

rattus

Senior Member
No, no, no!

No, no, no!

I dont know why, but what mlnk says makes sense, and what rattus says makes sense too. Its like light wave/particule duality. For some cases you use wave (refraction) and for other you use particule (reflection). In this case, for some cases you use Amps per hour (physical view), and for others just Amps (engineer view).

If we say amps/sec for example, we are really saying joules/sec^2 which is the rate of change of current which is physically correct but is of no interest to the electrician. Same argument applies to watts/hour.

Now ampere-seconds and watt-seconds are correct and are of interest, for example,

Batteries are rated in ampere-hours,

Energy usage is measured in kilowatt-hours.
 

Mayimbe

Senior Member
Location
Horsham, UK
dont see your point rattus, you have just said exactly the opposite you said before. Or thats what I understood of your last couple of posts
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
What mlnk says makes sense because it is expressing a basic concept that is found in reality. What he said is _incorrect_ only because he got the unit names wrong; but change the names and the concept is correct. I would also suggest that rather than saying particular units are meaningless, one should say that they usually mean something different from what people think they mean.

A coulomb is a particular number of electrons.

An ampere is a rate, which is a _ratio_ of a number of electrons and an amount of time. The thing about a rate is that you need neither a particular total number nor a particular amount of time; you just need the ratio. An analogy is that you can go at a speed of '60 miles per hour' without having to go 60 miles and without having to go for an hour. An ampere is a rate of 1 coulomb of electrons per second. An ampere can flow for 1 second or 1 hour or 0.0000001 second; in each case a different total number of electron movements will have been measured, but the rate is the same.

With electricity it is very common to take the rate units and turn them into quantity units. A watt is a rate of one joule per second. But people commonly use the term watt hour to mean the total number of joules if one watt were supplied for one hour. One watt hour is exactly 3600 joules. One watt hour is a quantity, meaning a certain number of joules; and this says nothing about the rate of its delivery. A 3600 watt load consumes one watt hour in one second; a 0.001 watt load would take about half a year to consume one watt hour.

Amps per hour or watts per hour are _not_ meaningless; but since amps and watts are both already rate units, these are thus rates of rates, or accelerations. People often say 'watts per hour' when what they really want to know 'kilowatt hours' per hour. In other words they want to know a rate (quantity per unit time, but expressed in the units that they are billed in) but they use units that mean an acceleration. Properly used, 'watts per hour' expresses the rate of change of power.

-Jon
 

rattus

Senior Member
Yes, but:

Yes, but:

dont see your point rattus, you have just said exactly the opposite you said before. Or thats what I understood of your last couple of posts

I should have said "amps/hour" is meaningless to the electrician, but is physically correct. I was trying to keep it simple because cbs/hour^2 requires a basic knowledge of calculus to comprehend and merely confuses the issue.

Shop talk often contains misused words and phrases, and somehow the job gets done. The purist however insists that units be used correctly. In solving problems and deriving forumulae for example, one verifies that the units are correct. If one throws in an extra "second" for example, the formula will be wrong!
 

rattus

Senior Member
Amps per hour or watts per hour are _not_ meaningless; but since amps and watts are both already rate units, these are thus rates of rates, or accelerations. People often say 'watts per hour' when what they really want to know 'kilowatt hours' per hour. In other words they want to know a rate (quantity per unit time, but expressed in the units that they are billed in) but they use units that mean an acceleration. Properly used, 'watts per hour' expresses the rate of change of power.

-Jon

Sure Winnie, but how many electricians care about acceleration except in their trucks?
 

mlnk

Senior Member
The reason I say amps per hour is so the student will see that it is different from amps per second. I am not talking acceleration. I think we remember from physics class that feet per second per second is a rate of acceleration. But it relates to electrical work only when you fall off a scaffold. Electricians don't talk about coulombs or joules very much but amps, volts, watts, and ohms quite a bit.
Also, light energy is depicted as wave energy. I think every electrician knows that electricity is moving electrons, physical particles that have mass.
 

iMuse97

Senior Member
Location
Chicagoland
To get the number of electrons that actually cross a point, we have to integrate the amps over time. For our original post, that just means we have to multiply the amps by the amount of time.

I'm sure everyone understands this, but I just hate to see the language get so relaxed that we use phrases like "electrons per amp" or "per" when we mean "multiplied".

Steve
I agree about getting the terms right. In that vein, the term for amperes x hours is Ampere-hours, abbreviated Ah. See below from Wikipedia:

An ampere-hour or amp-hour (symbol Ah , A?h, A h) is a unit of electric charge, with sub-units milliampere-hour (mAh) and milliampere second (mAs). One ampere-hour is equal to 3,600 coulombs (ampere-seconds), the electric charge transferred by a steady current of one ampere for one hour.[1]
The ampere-hour is frequently used in measurements of electrochemical systems such as electroplating and electrical batteries.
The commonly seen milliampere-hour (mAh or mA?h) is one-thousandth of an ampere-hour (i.e., 3.6 coulombs), and is a technical term for how much electrical charge a particular battery will hold. Small batteries, such as those in laptops and digital cameras, are often rated in milliampere-hours. The Faraday constant is the charge on one mole of electrons and is approximately equal to 26.8 ampere-hours, and is used in electrochemical calculations.
 

iMuse97

Senior Member
Location
Chicagoland
And now I see that all of you have already eleborated on this subject at length, while I failed to notice a whole second page of posts.
 
Last edited:

rattus

Senior Member
Proper use of amperes/second:

Proper use of amperes/second:

The formula, e = -L(di/dt), computes the voltage induced in an inductor, L, by a change in current. di/dt is this change expressed as a rate with the units of amperes/second. The negative sign indicates that the induced voltage opposes the change in current.

Now, I will venture to say that few if any power engineers ever use this formula--and even fewer electricians will do so.
 

rattus

Senior Member
??

??

The reason I say amps per hour is so the student will see that it is different from amps per second. I am not talking acceleration. I think we remember from physics class that feet per second per second is a rate of acceleration. But it relates to electrical work only when you fall off a scaffold. Electricians don't talk about coulombs or joules very much but amps, volts, watts, and ohms quite a bit.
Also, light energy is depicted as wave energy. I think every electrician knows that electricity is moving electrons, physical particles that have mass.

Mink, I don't get it. If you are saying an ampere for an hour, that is an ampere-hour, not an ampere/hour. You are muddling the minds of your students.

I have a night light which draws 33mA 24 hours a day, 720 hours/month, 8640 hours/year. Now which of these numbers will I use to specify the current?
 

mivey

Senior Member
The reason I say amps per hour is so the student will see that it is different from amps per second. I am not talking acceleration. I think we remember from physics class that feet per second per second is a rate of acceleration. But it relates to electrical work only when you fall off a scaffold. Electricians don't talk about coulombs or joules very much but amps, volts, watts, and ohms quite a bit.
Also, light energy is depicted as wave energy. I think every electrician knows that electricity is moving electrons, physical particles that have mass.
Well, you are going to instill bad habits in your students. That is like saying miles per hour per hour or miles per hour per second.

You can talk about what you think electricians do, but this electrician would not use that terminology, even before I became an engineer. If you find electricians using the terminology you are using, then they have some bad habits that should be corrected.

You are a teacher and should be held to a higher standard. You may not have known better before, but now you do. Stop doing that.
 

Mayimbe

Senior Member
Location
Horsham, UK
Also, light energy is depicted as wave energy. I think every electrician knows that electricity is moving electrons, physical particles that have mass.

Not always my dear friend. Through the work of Max Planck, Albert Einstein, Louis de Broglie, Arthur Compton, and many others, current scientific theory holds that all particles also have a wave nature (and vice versa).

I hope you have heard of any of those mentions above... :D
 

mivey

Senior Member
Not always my dear friend. Through the work of Max Planck, Albert Einstein, Louis de Broglie, Arthur Compton, and many others, current scientific theory holds that all particles also have a wave nature (and vice versa).

I hope you have heard of any of those mentions above... :D
And some recent cool stuff is that they think electrons can disappear from one point in space and re-appear in another.
 

quogueelectric

Senior Member
Location
new york
Actually an ampere is a rate. If you had an AC circuit in which one electron passed the same point 6.24 x 10 to the 18th power times in one second while moving back and forth you would have an amp with only one electron.

Asking how many electrons make an amp is like asking how many water molecules make a GPM.

This would be a very high frequency like a dog whistle for an alien.
 

Mayimbe

Senior Member
Location
Horsham, UK
And some recent cool stuff is that they think electrons can disappear from one point in space and re-appear in another.

quantum physics are quite extraordinary. When I first heard of this subject from my last physics course, I was astuned. I remember that the professor said to us, "All the knowledge that you have learned in the past couple of years of classical physics, you can take it all and throw it away from this day on"... quite amusing.

So that said, It doesnt surprise me, well it does in a way thats a new thing that I didnt know, but in other way it doesnt because I remember that my professor said that there were LOTS and LOTS and LOTS of things that were to be discovered in the quantum physics.

This professor is a great physician (dont know if its said that way), and one day he said to us, that he had been in lots of university all over the world due to his work. And he said that "From a physician perspective the only engineer from what I have seen thats its capable of understand, assimilate and care about all things that we physicians do, is the electric engineer. They can easily do the cross over to good physicians". Those words made me fell very good, I must say :D
 

mivey

Senior Member
quantum physics are quite extraordinary. When I first heard of this subject from my last physics course, I was astuned. I remember that the professor said to us, "All the knowledge that you have learned in the past couple of years of classical physics, you can take it all and throw it away from this day on"... quite amusing.

So that said, It doesnt surprise me, well it does in a way thats a new thing that I didnt know, but in other way it doesnt because I remember that my professor said that there were LOTS and LOTS and LOTS of things that were to be discovered in the quantum physics.

This professor is a great physician (dont know if its said that way), and one day he said to us, that he had been in lots of university all over the world due to his work. And he said that "From a physician perspective the only engineer from what I have seen thats its capable of understand, assimilate and care about all things that we physicians do, is the electric engineer. They can easily do the cross over to good physicians". Those words made me fell very good, I must say :D
I think the word would be physicists. All the physics professors I had were math geniuses. They just seemed to love that stuff. I'm not that much of a math nut, but there are times I wish I were.
 
Status
Not open for further replies.
Top