Electron path of travel

[trem]

You can, but you have to appreciate that the water represents the charge carriers, not the electric current that everyone is interested in.

When water flows in a pipe then we say there is a current. If the water stops flowing then there is no current. So which way does the current flow?
Of course, there is no answer, because current is not a moving object. It is simply a label we give to the phenomenon of the water moving.

It is exactly the same with a marathon. People can move, and flow in a discerible direction. Together they constitute a marathon. But the marathon does not flow anywhere.

I am not sure I understand what you are saying.
If the water stops flowing, there is still current (the water) but there is no voltage (the pressure). I thought that was the point of the water anaology.
In the USA, we have a 3 wire power cord. The Hot wire has 15 amps and 120 Volts. The Neutral wire has 15 amps and Zero volts. If the current does not move, isn't it still there..? If you grab the Neutral and the Ground wire, do you get pushed..? But if you grab the Hot wire and the Ground wire, what happens..? Both wires have the same current.
Aren't you talking about Voltage and not Current..?
Thank You

[guitarmike2107]

Ok lots of good arguments here and allot of BS too. here’s how I see it

Every reference I can find indicates that current is a flow, a flow of charge (coulombs), current is a scaler quantity not a vector, and so does not represent a direction.

As far as I can see the water analogy is water tight . the maths/calculations show this

1 column = -6.24151 × 1018 electrons.
1 litre = xxxx molecules of H2O (Assuming water of course and could be measured in pints/cubic metres/cubic feet etc)

Current = Coulombs/second
Flow rate = Litres/second

Both are scaler amounts

Going even further , Ohms law translates into water flow in a pipe too

Electrical Current = Voltage drop / Resistance
Water flow rate = Pressure drop / Pipe Resistance (Poiseuille's law)

Then taking another step further for power calculations

Electrical Power = Voltage x Current
Water power = Pressure Differential x Flow Rate

Both Ohm's law and Poiseuille's law illustrate transport phenomena

Transport phenomena (engineering & physics) - Wikipedia, the free encyclopedia

[Merlinb]

The Neutral wire has 15 amps and Zero volts. If the current does not move, isn't it still there..? If you grab the Neutral and the Ground wire, do you get pushed..? But if you grab the Hot wire and the Ground wire, what happens..? Both wires have the same current.
Aren't you talking about Voltage and not Current..?

A pipe can be pressurized even though no water is flowing. Hence there is no current in the pipe.
If nothing is plugged into the wall socket then there is no electrical current flowing, but a voltage (analogous to pressure) still exists between the live and neutral.

[Steve Conner]

With all this talk of pixels and Pong, I think Merlin has been smoking his magic tobacco again. Electron - Wikipedia, the free encyclopedia

In the water analogy, current is water flow in litres per minute or whatever unit you choose. Voltage is pressure, in psi or whatever. (The really old electrical textbooks even used to call voltage "pressure".)

You can think of the pressure as being caused by head of water above ground, in which case the B+ is like the water tank in the attic, and the water flows downwards, like conventional current in a well-drawn schematic. The analogy here is between electrical potential, and gravitational potential.

There are also mechanical and thermal analogs of electrical circuits, or maybe it's more accurate to say that the other way round. In the olden days you used to use these to set up an analog computer to solve a problem in fluid flow, dynamics or heat transfer. An analog computer was basically a big network of op-amps, and the graphs of voltage vs. time inside the computer were your results, the voltage standing for whatever you set it up to be.

This is the origin of the term "analog electronics", in fact. Nowadays we still do it, ironically simulating the analog circuit with a digital computer in PSpice.

[Wilder Amplification]

All I'm saying is that on the threads where the OP is asking the most basic of basic questions we should keep the discussion basic.

On the threads where the OP is asking things about load lines, scope plots, mathematical and engineering data, we post up that kinda stuff.

And on threads that ask about things not physically flowing in a wire we talk about that.

There are threads for every level of discussion. This one happened to be a thread regarding discussion of the basics. For the sake of not confusing the OP we should've left it basic...not go off on a quantum physics tangent.

For the record I think Merlin's book is a great book and I plan to by a copy myself. However, the one thing I didn't agree with in it was using conventional current flow as the means to describe valve operation as valves are in fact an electron device and it leads to confusion because of this. Just my $0.02.

[Merlinb]

In water, Current is the flow of a quantity, that quantity is measured in litres/pints/cubic metres, 1 Litre = xxx Molocules of H2O (charge carriers)
In electronics, Current is the flow of a quantity, that quantity is measured in coulombs, 1 coulomb = -6.24151 × 1018 electrons (charge carriers)

Both measurements are scalar properties. i.e. don’t have a direction/not vector based.

Exactly. The concept of direction does not apply to current (which is scalar). So when the OP asked (paraphrasing) "what direction does current flow?" one might as well ask "are bananas good or evil?". The question is unanswerable. (which makes it a philosophical question in my book, like all nonsense questions!)

[Wilder Amplification]

I am not sure I understand what you are saying.
If the water stops flowing, there is still current (the water) but there is no voltage (the pressure). I thought that was the point of the water anaology.
In the USA, we have a 3 wire power cord. The Hot wire has 15 amps and 120 Volts. The Neutral wire has 15 amps and Zero volts. If the current does not move, isn't it still there..? If you grab the Neutral and the Ground wire, do you get pushed..? But if you grab the Hot wire and the Ground wire, what happens..? Both wires have the same current.
Aren't you talking about Voltage and not Current..?
Thank You

Actually it's the flow of the water that is the "current" just as it is the flow of electric charge that is the electrical current. When you have no current but you have a charge differential between two points (i.e. a "potential" or a "voltage"), current can POTENTIALLY flow between said two points once the circuit is completed (hence the name "potential"). However, there is no actual current flow if the circuit is broken, yet the charge differential between the two points still exists.

It is the charge carriers themselves that are always present in a conductor. However, the flow of said charge carriers only exists if you have a difference in charge carriers between two points in a circuit, which is the charge differential.

When you touch the hot and neutral, your body poses a resistance to these said two points, which completes the circuit, current now flows and you get the shock.

While you may have a charge differential between the two points, it is not a quantifyable differential until you complete the circuit. When you measure voltage, the internal resistance of the meter completes the circuit, current flows through the internal meter resistance and the meter either -

A) Can measure the current and calculate the voltage based on the known value of its internal resistance

B) Simply measure the voltage drop across its internal resistance

This is where the resistance to current flow creates a definable voltage. Current has to be flowing through a resistance in order for you to have a definable voltage (simple Ohm's Law...E = I x R).

Fun fact...current on the neutral is always equal two the difference in current on the two outer legs. This is because the neutral is the center tap of the utility mains transformer secondary and is common to the two outside "hot" legs. The two outside legs are differential relative to the neutral center tap (i.e. they're 180* out of phase). This means that when leg 1 is positive the neutral center tap serves as its negative while at the same time the neutral center tap is serving as the positive for leg 2, which is negative when leg 1 is positive.

If both legs are sourcing identical amounts of current, you have a balanced load condition and the difference between the two is zero, which makes the current on the neutral center tap zero as well. In an unbalanced load condition (i.e. one leg sourcing more current than the other), current on the neutral is equal to the difference in current flow between the two outer legs.

[defaced]

Merlin,

Could you please provide comment to my post linked here: http://music-electronics-forum.com/t22755-3/#post191920

I am very interested in reading your thoughts on drift velocity and the notion that current does not have a vector direction.

Thanks,
Mike

[guitarmike2107]

Electrons move in a direction, lets call that direction x, so their velocity =

V = dx/dt

So from the calculus equation you can see that their movement is directional (dx) and therefore vector based


Current is a measurement of a quantity of charge passing in a specific time
I = dQ/dt

So where is the vector direction in that?

[Steve Conner]

Current is a vector, at least it appears as one in Maxwell's equations. Current density - Wikipedia, the free encyclopedia

[guitarmike2107]

Yes but current density (A.m^2) and current (A) are not the same thing..

m^2 is a vector which is why current density is a vector

Charge and time are both scalar, which is why current is scalar

[Steve Conner]

No, you've got it the wrong way round. Current and current density are both vectors, the area is the scalar.

Of course you can quote either as a scalar, the unwritten assumption being that the current is flowing along some conductor that fixes its direction. (To get the vector version, you multiply by a unit vector parallel to the conductor.)

[guitarmike2107]

To get the vector version, you multiply by a unit vector parallel to the conductor.)

ok, so what is the units of your co-ordinate system that your unit vector is in, metres?
so you end up with A x 1m (Amp.metres) which agian is a vector because you have just added a direction.

ok, I give up my head is too sore to keep going on with this, Someone else can argue... erm debate if they want to.

[Steve Conner]

You're getting dimensions and directions mixed up.

1 mile is a scalar, so therefore is 1 square mile, cubic mile etc.

1 mile north-northeast is a vector.

[guitarmike2107]

You're getting dimensions and directions mixed up.

1 mile is a scalar, so therefore is 1 square mile, cubic mile etc.

1 mile north-northeast is a vector.

You're getting dimensions and directions mixed up.

1 mile is a scalar, so therefore is 1 square mile, cubic mile etc.

1 mile north-northeast is a vector.

Actually I am not, by multiplying by a vector you are assigning direction to the scalar, a vector by default must have direction, that’s the point I was trying to make,

Even in your example you have to add additional information to the scaler to make it a vector, either an angle, north-northeast, or an X - Y - Z orientation.
i.e. 1 mile is still a scalar, just as 1 Amp is still a scalar, until you add the additional directional information.

Thinking about this further, and I wish I wouldn’t, the direction which you assign is based on the voltage polarity.

What about AC currents in a resistive circuit, The electron flow direction is changing all the time based on the AC voltage but the measured(average) current stays constant

ok I said I would stop, I really must .........