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HeavyToilet
The Heaviest OfThem All


Registered: 08/06/03
Posts: 9,458
Loc: British Columbia
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Really basic electrical circuit questions...
#14557841 - 06/03/11 09:55 PM (12 years, 8 months ago) |
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Just so you guys know, I've tried to read everything on Wikipedia (and more) about this, but there are still things I do not understand.
So here are some questions which I've been wondering.
I understand that an electric potential difference could be thought of as energized electrons, which want to go to where there are the positive charges (or "holes") they can get to.
So one end of the circuit you have these energetic electrons (which not only want to get to a hole, but want to get away from each other), then at the other end you have a positive charge.
This is accurate, correct?
I also understand that a ground is attached to at least one node in a circuit.
I don't really understand a ground.
Why don't the electrons just go down the ground when then the circuit is closed? Is it because the holes have a greater positive charge than ground, so electrons don't even bother going down that path?
Also, if my description of how potential difference is accurate, then how can voltage easily be changed with a power supply? There's a lot of energetic electrons on one side of the circuit, and a lot of positive charges on the other side. How does one change this? Does it somehow change how energetic the electrons are, or how many holes there are? Or what?
And on the same topic, Wikipedia says that ground used for if there is suddenly a huge potential difference. Would that be because there's a huge amount of electrons on the surface of a conductor (the wire), and force pushing them outward, away from each other would overwhelm the force they would have towards the positive charge at the other end of the wire (and I guess to the protons in the conductor)?
And this is related to the question before the last: what would cause such a sudden increase in voltage? You'd either have to increase the number of electrons, their energy, or increase the number of holes significantly, right? Would an example of this be lightning striking a power line? What are other examples?
Edited by HeavyToilet (06/03/11 10:17 PM)
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Bacchus
Lurker




Registered: 10/10/06
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Re: Really basic electrical circuit questions... [Re: HeavyToilet]
#14558296 - 06/03/11 11:36 PM (12 years, 8 months ago) |
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Quote:
So one end of the circuit you have these energetic electrons (which not only want to get to a hole, but want to get away from each other), then at the other end you have a positive charge.
Yep
Electrons don't go to ground because they come from ground. Well, more accurately, the electrons in the conductors used for the circuits are pushed away from ground. Anyway, ground is the negative terminal.
As for power supplies, there are different answers. If it's AC and a transformer that we're dealing with, then the power supply is taking advantage of electrical inductance and the relationship between the number of turns in a coil and the EMF that is acting on it. Three things are needed to generate electricity: A conductor, a magnetic field, and relative motion between the two. The ratio of turns between the primary and secondary coils of the transformer dictates the current (and by Ohm's law, the voltage.)
Solid state, DC voltage regulators are a little more involved and invoke feedback loops and reference voltages. I never gained a clear understanding of solid state mechanics beyond what's going on at PN-junctions.
I guess I don't really understand your last question. Ground is the reference that voltages are measured against. Voltage is just a difference in electrical potential (between ground and something else). In practical terms, yeah lightening rods are just conductors that run from above your house to an iron rod that is driven deep into the earth (ground). That's a case of negative voltage. When circuits are encased in metal (dryer, toaster, etc) the metal housing is connected to ground. This is to protect the user in the event that some wire comes loose and contacts the housing. Rather than the appliance turning into a booby-trap waiting to shock you, a direct short to ground is created. Given the choice of a direct short with nearly zero resistance or the flesh of a human with resistance measuring in the megaohm range, electrons and holes will take the easy path. And besides, the direct short creates a current approaching infinity and will trip the circuit breaker in your house, saving the day.
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Seuss
Error: divide byzero



Registered: 04/27/01
Posts: 23,480
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Re: Really basic electrical circuit questions... [Re: HeavyToilet]
#14559745 - 06/04/11 11:48 AM (12 years, 8 months ago) |
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Stop thinking about electrons and start thinking in terms of charge. Sure, electrons are the 'thing' that makes all of this work, but it is charge that we really care about.
Quote:
I understand that an electric potential difference could be thought of as energized electrons, which want to go to where there are the positive charges (or "holes") they can get to.
So one end of the circuit you have these energetic electrons (which not only want to get to a hole, but want to get away from each other), then at the other end you have a positive charge.
This is accurate, correct?
Electric potential is the energy required to move a unit of electric charge. Again, think in terms of charge, not electrons.
Quote:
I also understand that a ground is attached to at least one node in a circuit.
I don't really understand a ground.
Ground is simply the point of lowest electric potential in a circuit. Most circuits are tied to earth ground, thus the circuit ground is at the same potential as earth ground. However, this is not mandatory. If a circuit ground is not tied to earth ground, it is said to float. A floating (circuit) ground can have a large potential difference between it and earth ground (which can shock the hell out of you if you aren't paying attention).
For the most part, you can simply think of 'ground' as a point of zero volts in a circuit.
One last thing to watch out for... when you start looking at charge, some texts will claim that charge flows from positive to negative while other texts will claim that charge flows from negative to positive. As long as you are consistent, it doesn't matter which one you use. However, things can get confusing if you switch between texts where one text uses one direction and the other text uses the other direction.
Again, think in terms of charge, not electrons.
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DieCommie

Registered: 12/11/03
Posts: 29,258
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Re: Really basic electrical circuit questions... [Re: HeavyToilet]
#14559890 - 06/04/11 12:32 PM (12 years, 8 months ago) |
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Edited by DieCommie (11/10/16 07:19 PM)
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