A question on basic electricity and a theory

In New Zealand some years ago due to pressure from Greenies wanting to power their own homes with photo-voltaic energy or windmills etc a previous government instituted law changes obliging the power companies to purchase spare energy from small household generators.

This required some form of transformer and metering to be able to measure the flow in from the national grid or out from the household.

Originally posted by Mayson

Originally posted by jaynkeel
reply to post by Mayson

 

Kinda hard to tell who your post is directed at. This thread isn't about gaining free electricity sorry if you were misinformed.

I could have sworn that your original post was hinting that you wanted to make money by selling back the electrons that you didn't use to the power company.

No just want to make sure I am not paying for something that I am not totally using, and my main problem with the meters that the electric company uses is trusting them to be totally accurate. The same as if you went to a gas station and paid for a gallon of gas and only received a portion of that gallon. We have to solely trust that they are being honest with the readings that I have a problem with.

reply to post by jaynkeel


It may be the case that your energy company is defrauding their customers, but it's absolutely not the case that you could save money by not allowing the charge coming into your house to flow back out into the grid. If you're being taken advantage of, it's definitely not in the way that is suggested in your OP. The power company's meter measures the difference between what is going in and what is coming out, not just what is going in. This system makes no distinction between you using the power in real time or storing it for later, so even if you decided to store some of the energy instead of returning it to the grid you would be no better off as the stored energy would show up as part of the total in/out difference. There's no way around this because you have to have power flowing both in and out in order for it to flow at all.


You can prove this to yourself by buying a battery and connecting it to a device. In this experiment you can think of the battery as the grid and the device as your house. See what happens if you only connect one contact of the battery to the device, or if you siphon off some of the power to another battery for storage. You can play around with this configuration, and you can buy and ammeter and voltmeter both for less than 50 dollars. You could use these devices to determine all of the relevant variables. You'll find that in order for the devices to be powered, the charge must pass through the device; it can't flow in without also flowing out. Remember that watts equals volts times amps.

If you really want to get into it, you can buy a home energy monitor for less than 200 dollars. If you hook this up to your power cables it will tell you the difference between what is coming in and what is going out, which would be equal to what is being used up in your house. You can compare this to what your being billed for and see if there is a large difference. A small difference, either up or down, would be expected because the power company bills you based on your average use for a billing cycle.

The potential for abuse by the power company has nothing to do with the properties of electricity. You're suggesting that they're just lying to you about how much of their product you're using, so that they can bill you more. This doesn't really make sense. It's easy enough for you to investigate and the legal and PR risks great enough that it would never be worth it for the company. Not to mention, they can just charge you more for the power that you are using. That's what they do if they want to make more money. They can charge whatever they want, they don't have to come up with a scheme to lie about how much you're buying.

They're selling something that is in high demand and they can set their own price. The idea that they're consipiring against you in order to raise your bill is paranoia getting the best of you; it's a complicated and risky way for the company to achieve something that they could achieve much more easily by simply raising their prices. Your fears are unfounded.

Originally posted by ben91069

This flow of current is instantaneous, traveling through the conductor at nearly the speed of light, because it is an electromagnetic energy.

The potential gradient forms at the speed of light in whatever medium it's in - for a cable it can be comparatively slow compared to the speed of light in a vacuum - but the current flow is actually quite slow in comparison, it can be a dead crawl at low currents. A good conductor has a LOT of electrons per unit volume.

Originally posted by R3KR

PS: Would it be fair to think electrons are all places at once ?, they are just a ripples of energy in the fabric of space time, hence, being they are actually space time being rippled, they dont really exists. But of course we create models for them so that electrons seem to exists, so we can calculate power/force...ect ?

edit on 16-10-2010 by R3KR because: (no reason given)

No, you can calculate the likelihood that an electron is in any volume - they're discrete particles. You can make a stream of them with proper electron optics and shoot them like a firehose, in a vacuum.

I have heard some people ruminate that all electrons are the same electron, just going back and forth in time, but generally only when they're drunk. There also used to be some guys working on a theory that electrons were paired or multiply linked, and that you could cause one to move here and get motion from its partner over there somewhere using some weird non-local action, but I don't know if it ever amounted to anything, I don't work there anymore.

Originally posted by Bedlam
The potential gradient forms at the speed of light in whatever medium it's in - for a cable it can be comparatively slow compared to the speed of light in a vacuum - but the current flow is actually quite slow in comparison, it can be a dead crawl at low currents. A good conductor has a LOT of electrons per unit volume.

This is totally incorrect. The current flow through a conductor travels at nearly the speed of light, because what is happening is one electron from an outer energy valence shell is being replaced by an extra valence electron in an energy shell of an adjacent atom made of the same conductive material.

Current always travels at the same speed in any homogeneous conductive material without regard to the amount of current which is a measure of the quantity of electrons flowing across a static point per second.

Good conductors are conductors which have an abundance of free valence electrons in its outermost energy level or shell. The volume of the conductor will determine only the electrical resistance of the conductive material per length.

Quite a few posters in here have got it completely wrong so I can help being an electrician, AC is a sinusoidal waveform of Votlage ( ie switches back and forth + to - 50 times a second ) this cycling is done initially back at the Power Station by a spinning Generator which is in turn fed through various distribution transformers and stepped up in amplitude to be transmitted vast distances then stepped back down via the various switching stations and transformers in your town/vcity.

Electrons, which invariably provide the energy do return to the Generator from your house because they have to to produce a circuit. How ever when you look at the real circuit you will find that the transformer your street is on is isolated from the Power Station via a delta - star Transformer configuration and technically only the primary side of the transformer's windings electrons go back to the secondary winding of the step up transformers back at the Power Station.

So simply put, your House's Power only loops back to the secondary winding of the Distribution Transformer located in your suburb because its hooked up to the secondary winding which is electrically insulated from the primary side.

There is one way you can actually get more electricity for free and it has to do with power factor manipulating because you only pay for "True Power" and not "Apparent Power" which can save you a few dollars by having more of an inductive type load in your house. That's all I am going to say about it.

Originally posted by ben91069
This is totally incorrect. The current flow through a conductor travels at nearly the speed of light, because what is happening is one electron from an outer energy valence shell is being replaced by an extra valence electron in an energy shell of an adjacent atom made of the same conductive material.

Current always travels at the same speed in any homogeneous conductive material without regard to the amount of current which is a measure of the quantity of electrons flowing across a static point per second.

Good conductors are conductors which have an abundance of free valence electrons in its outermost energy level or shell. The volume of the conductor will determine only the electrical resistance of the conductive material per length.

Wrong, wrong, wrong, my friend.

The volume of the conductor does determine the electrical resistance of the material per length, correct.

The current is a measure of the quantity of electrons flowing across a static point per second, correct.

Current flow in a conductor is trading valence electrons like a relay race - wrong, it's more like an electron gas that's not tightly bound to any one nucleus.

However, you seem to be envisioning the current flying out of the source and through the load in valence tradeoffs. It doesn't work that way. Go check out the Drude model and drift velocity - that's the way it actually works, with some mods for quantum effects brought in by Bloch, Debye and Fermi. (and a couple of error corrections that somehow cancelled out originally, for the most part) The speed of net electron motion in a metallic conductor is actually quite slow - the potential field propagates at the speed of light in the medium, the electron motion is glacial.

Most of the net articles on Drude electron drift velocity are pretty eggheaded - I'm assuming you aren't going to want to deal with the math in the raw - so here are a few links that are more talky than quantum physic-y.

Speed of electricity - amasci
Hyperphysics, wherein it's shown I'm right about the drift speed being related to the conductor material and size
The inevitable wiki article that shows the same thing, with more math
The same material more obscurely from RPI

There's a million others - what you describe sounds like something taught to electricians. It doesn't work that way. We've been using some version of Drude current flow theory since about 1900, even in EE, which is pretty boiled down from the way the physics guys look at it. The field follows the conductor, a large but apparently fictitious energy flux follows the field, the Poynting vector describes the tiny amount of that that's diverted into the wire as potential gradient, the electrons flow slowly, at a rate related to the current, the conductivity, and the size of the conductor. Not electrons shooting out of the battery, around the loop and back in at light speed.

Originally posted by ben91069
This is totally incorrect. The current flow through a conductor travels at nearly the speed of light, because what is happening is one electron from an outer energy valence shell is being replaced by an extra valence electron in an energy shell of an adjacent atom made of the same conductive material.

Current always travels at the same speed in any homogeneous conductive material without regard to the amount of current which is a measure of the quantity of electrons flowing across a static point per second.

That's not quite right. The definition of current is "charge flow rate." The rate at which the charge flows in a conductor is the net rate at which the electrons flow, because electrons are the charge carriers in conductors, such as wires. The standard unit for current is the ampere, which is equivalent to one coulomb per second. A coulomb is a specific number of electrons (~6.2*10^18).

Given this definition, it doesn't really make sense to talk about the speed of current. Current refers to the amount of electrons that move through a cross-sectional area in a certain amount of time. If there are many free electrons moving in the same direction slowly the conductor can have the same current as if a small number electrons were moving very quickly.

The electrons in a conductor that is not expose to an electic field move around randomly. Their motion does not exhibit a tendancy towards any one direction, so there is no net flow of charge. When an electric field is applied, the electrons move along the conductor in response to the field. This motion is no longer random and a net flow in one direction exists. The rate at which electrons make their way along the electrified wire is called the drift rate, and is a function of the strength of the electric field, among other things. This rate is slow; around a millimeter per second in copper wire. The drift rate is the net movement of electrons, which is different than the velocity of any given electron. Individually the electrons are moving quickly, but they bounce around enough that much of their motion is still random, which means that net progress is not made very quickly.

The velocity of the electrons individually in a copper wire or other conventional conductor is fast, but not near the speed of light. They travel at around a million meters per second, and light travels hundreds of times that fast. The thing that moves quickly is the electromagnetic wave, which propagates at nearly the speed of light. This, despite the fact that the net motion of the electrons and therefore the net transfer of charge (which is current) is much slower. It is the electromagnetic wave that transmits signals quickly, or causes the light to turn on as soon as you flick the switch. Voltage propagates at the speed of the wave, which means that usable power is delivered very quickly to the entire curcuit

Edit to add: I don't mean for there to be an echo in here, sorry. I started this reply before Bedlam had made the post right above, in which he makes a similar point (using more sophisticated concepts).