Consolidate my understanding.. (1 Viewer)

[GaDaMIt]

Just a quick bit of theory that isnt really required but I feel I need to understand these finer details.

By the Right hand palm (push) rule you get that conventional current is the direction your thumb points in.
But conventional current is the direction in which protons travel. Thus, the terminal they reach becomes positively charged.
But also protons travel from positive terminal to negative terminal. So wouldnt this like screw up the system?
I understand that in reality protons dont move only electrons do, so then tell me why the converse works for electrons? That would still screw up the system right?

I dont do chemistry so if thats involved please provide some sort of an alternate explanation?

 

[alcalder]

Conventional current is the direction of flow of positive particles.

This was defined before they found out that current is actually the flow of negatively charged electrons. Thus conventional current is in the opposite direction to the flow of particles that causes it.

SO, when using the Right Hand Rule, just remember

THUMB = direction of conventional current/positive particle flow.

If you have electrons then point your thumb in the opposite direction to their flow.

Does that help?

 

[xiao1985]

@OP:

everything you said was right except this:

Thus, the terminal they (protons) reach becomes positively charged.

proton will only travel from positive to negative... which means the terminal they travel to is BECOMING more posivitively charged, but really they are NEGATIVELY charged...

 

[GaDaMIt]

@OP:

everything you said was right except this:



proton will only travel from positive to negative... which means the terminal they travel to is BECOMING more posivitively charged, but really they are NEGATIVELY charged...

I think thats the answer to my question but i dont get it? Why is it really negatively charged when its becoming more positively charged

THUMB = direction of conventional current/positive particle flow.

If you have electrons then point your thumb in the opposite direction to their flow.

Okay then going by the fact that only electrons move. They go from negative to positive terminal right? So wouldn't they negatively charge the positive terminal somehow?

 

[Forbidden.]

Uhh ... I learned that protons usually don't travel but if they do the wire will be physically changed.

 

[alcalder]

Think of a power source as a pump that is pumping the water (electrons) up a long hill. The hill is then the circuit.

The electrons go from negative (the top of the hill) to the positive end (bottom of the hill) because of the nature of the source (pump).

The fact that the electrons then get to the positive end, does not make the positive end more negative, they just get pumped through to the negative side and go around again.

Does that make sense?

 

[ianc]

yeah the electrons don't just gather up one end but continue moving ROUND AND ROUND the circuit (hence the name "circuit"). The voltage provides energy to push the electrons - the electrons being negatively charged are always attracted to the positive end so this determines their direction.

You'll understand electrical conductivity a lot better after you've done the ideas to implementation topic, because it explains how the concepts of current and resistance at an atomic level.

If you're feeling adventurous, you could always skip ahead and read those chapters in your text book

 

[Forbidden.]

yeah the electrons don't just gather up one end but continue moving ROUND AND ROUND the circuit (hence the name "circuit"). The voltage provides energy to push the electrons - the electrons being negatively charged are always attracted to the positive end so this determines their direction.

You'll understand electrical conductivity a lot better after you've done the ideas to implementation topic, because it explains how the concepts of current and resistance at an atomic level.

If you're feeling adventurous, you could always skip ahead and read those chapters in your text book

ANALOGY:

So if electrons tried to travel through thin liquid (e.g 0.01 Ohm resistor) they can pass easily but if they try to pass through an extremely viscous liquid (e.g 10,000 Ohm) resistor they stop in their tracks ?

 

[xiao1985]

don't worry about becoming more positive part... just know that conventional current flow from positive to negative...

 

[GaDaMIt]

Its the induced current application thats confusing me. There was a question with a magnetic field going out of the page and a stationary coil with no current passing through it. It asked what would happen in the coil if the magnetic field was reduced to nil at a constant rate. Answer was that X becomes positive terminal

Umm i dunno how to upload pictures but the coil was shown as an upside down "U" (except edges were straight with 90' corners ) with the bottom left labelled X and bottom right labelled Y. Basically current direction was anticlockwise and thus the positive charge positively charged X. Now this is what is confusing me.

(Sidenote: Its from success 1 2006 page 51, if anyone has access to the book and can be bothered providing me with an explanation for this question id much appreciate it dont really like the answers...)

In a usual circuit wouldnt the same thing happen? As i asked above.. the positive terminal being negatively charged..

 

[xiao1985]

ok i see... i don't have the book but i get the picture...

firstly, the conventional current induced does go anti clockwise (hope you can see that too)

next, success is bs'ing... (success contains alot of errors... and they dont' seem to correct them)... if x is at bottom left, and y at bottom right, then y would have became the positive terminal and x the negative terminal (and hence conventional current goes from positive to negative, from y to x) if it is really a circuit...

however, if it's not a circuit (ie if the two ends does not connect else where, which by the virtue that it's a coil, seems unlikely) then the conventional current induced will cause the positive charge to go towards the x side and hence make x more positively charged than y...

 

[GaDaMIt]

firstly, the conventional current induced does go anti clockwise (hope you can see that too)

Just a quick question about that

Tell me if each of these are suitable expanations for what happens.. particularly the second, im not sure if its just coincidence..

ONE:From (|) = BA .. basically because the magnetic field is being reduced ( (|) is being reduced) and B remains constant, A must reduce by the equation. Therefore you want the coil to be pushing inwards by RHPR. From that you get current is clockwise, however this is induced and by Lenz's Law its becomes anticlockwise.

TWO: (this is the one where my reasoning im not too sure about. I think it may just be coincidence..
The reducing magnetic field into the page by Lenz's Law is opposed as such that it creates out of the page magnetic field. By the Right hand COIL rule (ringers curl in current direction, thumb to N pole) you get that current is anticlockwise?

 

[david294]

You know that in reality it's the electrons which move, however the right hand rule which you are using works for positive charges (its best not to say protons).
This rule applies to current being produced (ie generated), when a conductor moves in a magnetic field. there is initially no positive or negative end. You are right in that the end to which the positive charges move becomes positive. there are then two possibilities
first, if a circuit exists the charges just flow around the circuit
secondly, if no circuit exists one end of the wire becomes positive and the other becomes negative, this soon stops any more movement of charges.

 

[xiao1985]

@gadamit:

1) (I) = BA means magnetic flux = magnetic field strength * Area
when the field strength decreases, both (I) and B decreases, which at end equation holds... (yes B does decrease)

2) Is the reason why (or at least at my own reasoning) the conventional current generated is anti clockwise