This reminds me of an incident I read of in one of Winston Churchill's books -- I forget which one -- where he related a confusion between the American staff and the British staff over a phrase. The Americans were wanting to invade a region -- I forget which -- in concert with the British. Radio communications said that plan was "off the table," which to Americans meant abandoned, but to British meant it was what the Americans thought of as "on the table," and being worked on by staff. Fortunately, they got it sorted out.

P.S. Upon reflection I think I got it mixed up: The British use the term "on the table" to mean its being examined, while the Americans use the term "off the table" to mean the same thing. I'
m getting old.

So... are "you on the wagon", or "off the wagon" ?

 

Single phase!
Max.

The way I understand it... 120 VAC is single phase, and 220 VAC is double and triple phase... That is because in 120 VAC you have a live wire and a neutral, whereas in 220 both wires are live (and the third one too)... Then again, I might be starting yet another fundamentalist discussion here...

 

P.S. Upon reflection I think I got it mixed up: The British use the term "on the table" to mean its being examined, while the Americans use the term "off the table" to mean the same thing. I'
m getting old.

I've always heard it used as "on the table" meaning that it is being considered and "off the table" meaning that it isn't. The classic cliché being, "All options are on the table," or equivalently, "No option is off the table." The mental picture is simply one where all of the possible courses of action are in documents that are sitting on a table and available for discussion. Whenever a proposal is rejected, it is "taken off the table" and discarded so that it can no longer be confused with options still under consideration.

 

I've always heard it used as "on the table" meaning that it is being considered and "off the table" meaning that it isn't. The classic cliché being, "All options are on the table," or equivalently, "No option is off the table." The mental picture is simply one where all of the possible courses of action are in documents that are sitting on a table and available for discussion. Whenever a proposal is rejected, it is "taken off the table" and discarded so that it can no longer be confused with options still under consideration.

Unless you agree to get paid "under the table"...

 

Unless you agree to get paid "under the table"...

Yep -- though that brings up another usage. When you conclude a deal and didn't get the best deal you could have gotten, you are said to have left such-and-such on the table. The mental image I have there is that two parties come together to make a deal (perhaps splitting up the assets of an estate or a divorce) and put everything that is to be divided onto the table. Say one of those items was a jewelry box and neither party gave it much thought because they were focused on the stacks of money and stock certificates. So neither party said that they wanted the jewelry box (perhaps it was empty and neither party realized that the box itself was an antique that was worth more than all the money and stock combined) and once they were done one party takes the stuff they got and left. Since they didn't claim the box they leave it on the table when they are finished and, as a result, the other party gets it by default.

 

I don't know where the electron current flow debate has gone but it seems to have "drifted" way off course, possibly attracted by another "dark force".

 

So... are "you on the wagon", or "off the wagon" ?

Actually I had been drinking -- just a few beers, mind you.

 

The way I understand it... 120 VAC is single phase, and 220 VAC is double and triple phase... That is because in 120 VAC you have a live wire and a neutral, whereas in 220 both wires are live (and the third one too)... Then again, I might be starting yet another fundamentalist discussion here...

Single phase specifically means that the device it is driving, a motor, for example, is single phase. Whether you are running a 120 volt motor driving your refrigerator's compressor, or a 240 volt motor driving the blower for your furnace, they are both looking at single phase sources.

Incidentally, I've noticed many people in here using 220 volt, when it is really 240 volt. It's 120/240. That's what the National electric code says, anyway. These days the power grid is well regulated. In my neighborhood, anyway.

 

When I went to the university to get my BSEE we were taught current flows from positive to negative and we did all of our calculations with this convention. The textbooks throughout our electrical engineering courses used this convention. And yet we were taught the truth: that current actually flows from negative to positive. Nevertheless, science persists in the conventional positive to negative direction. The calculations are based on this presupposition and they work no matter which way the current actually flows. Okay, so far so good. But then I run into electrical technician sources and they insist on thinking in terms of negative to positive such that the little arrows on the diode and transistor symbols are backwards. Why is this counter intuitive system of thinking gaining ground? I, for one, will never draw my KVL loops backwards, for that would involve the complication of most of the numbers being negative. I like to work with positive numbers. Any thoughts on this?

Its probably easiest to remember by: The current flow in a thermionic valve (tube) is electrons being emitted by the hot cathode and being attracted by the positive anode (plate) - that is obviously electron flow. With a semiconductor diode, the arrow part of the symbol points in the direction of conventional current flow.

 

Its probably easiest to remember by: The current flow in a thermionic valve (tube) is electrons being emitted by the hot cathode and being attracted by the positive anode (plate) - that is obviously electron flow. With a semiconductor diode, the arrow part of the symbol points in the direction of conventional current flow.

So the unsurprising result here is in both a vacuum tube or a semiconductor diode the current flows in the same direction: anode to cathode (conventionally) or cathode to anode (direction of electrons).

 

So the unsurprising result here is in both a vacuum tube or a semiconductor diode the current flows in the same direction: anode to cathode (conventionally) or cathode to anode (direction of electrons).

But you are not using the same meaning of "current" in both cases. In the first case you are using current as being the flow of electrical charge and measured in amperes (coulombs per second). In the second case you are using current as being the flow of electrons and NOT the flow of electrical charge. What are the units of current in this case? It is NOT amperes.

 

But you are not using the same meaning of "current" in both cases. In the first case you are using current as being the flow of electrical charge and measured in amperes (coulombs per second). In the second case you are using current as being the flow of electrons and NOT the flow of electrical charge. What are the units of current in this case? It is NOT amperes.

Since when is the flow of electrons not the flow of electrical charge (where 1 electron has a charge of ≅ -1.60217657 × 10E-19 coulombs)?
And the flow is indeed measured in amperes (coulombs per second).

 

But you are not using the same meaning of "current" in both cases.

Correct and I say so.

 

Correct and I say so.

So what unit do you use for the flow of electrons?

 

Since when is the flow of electrons not the flow of electrical charge (where 1 electron has a charge of ≅ -1.60217657 × 10E-19 coulombs)?
And the flow is indeed measured in amperes (coulombs per second).

You have 'electrons/sec' not 'coulombs/sec'.

And coulombs is a signed quantity.

Look at your own figures. You acknowledge that an electron has a charge of NEGATIVE 1.602e-19 coulombs.

If you define your symbolic current flow as being positive in the direction that electrons actually move, then the current in that when electrons are flowing in that direction is NEGATIVE because you have a NEGATIVE charge flowing in that direction!

Let's say that we have two objects, A and B, initially uncharged.

Object A fires a stream of electrons at Object B at the rate of 6.24e18 electrons/sec. What is the current that is flowing from A to B? If you say 1 ampere, then you are saying that the flow of charge is +1C/s and that after ten seconds that the charge on B will be +10C.

In actuality, the electrical current from A to B is -1A because there is -1C/s of charge flowing in that direction.

It's somewhat like working with moles in chemistry. The mole is a count of the number of items of a substance. A mole of hydrogen gas has the same number of molecules as a mole of oxygen gas. But the mole is not the mass and if you want to express mass flow then you can't do it in moles/sec but, rather, you have to apply a conversion factor to get from moles to mass.

It's the same if you use charge carrier current. If you have 6.24e18 electrons/sec you do NOT have an expression of charge flow. Notice your own conversion factor

I = (N electrons/sec)·(-1.60217657 x 10E-19 coulombs/electron)

NOW you have a current expressed in charge/second and, that current is NEGATIVE in the direction that the electrons are moving.

 

The polarity of the charge doesn't change the fact that the flow of electrons is the flow of electric charge and it is measured in amperes.
Your are trying to split hairs when there are no hairs to split.

 

The polarity of the charge doesn't change the fact that the flow of electrons is the flow of electric charge and it is measured in amperes.
Your are trying to split hairs when there are no hairs to split.

If you consider being off by a minus sign to be splitting hairs, I sure hope I never let you jump start my car!

And why not answer the question?

Is the flow of charge (i.e., the current) from A to B equal to 1 C/s or is it equal to -1 C/s.

Or, since it's splitting hairs, is there no difference between the two?

 

WBahn
And coulombs is a signed quantity.

At last someone has acknowledged my post#18

 

..............................
And why not answer the question?

Is the flow of charge (i.e., the current) from A to B equal to 1 C/s or is it equal to -1 C/s.

Or, since it's splitting hairs, is there no difference between the two?

Of course there's a difference. Not necessary to be patronizing.

But you previously stated that
"In the second case you are using current as being the flow of electrons and NOT the flow of electrical charge. What are the units of current in this case? It is NOT amperes."
I don't understand how you can make that statement based upon the sign of the charges. Either way the charge flow is in amperes. The conventional current flow is from plus to minus, the electron flow is minus to plus.

 

So what unit do you use for the flow of electrons?

I use conventional current and I measure current in amperes.

Any problems?