How Fast is elcectricity

zero_cool · Mar 15, 2005

How fast is electricity?

yevaud · Mar 15, 2005

Slower than the speed of light, if that's what you need to know. This has been an interesting question for engineers and physicists for some time. It has been measured in a variety of mediums though, and it varies depending. For example, the flow of electrons has been measured at 4.62 meters/second down a a meter long copper wire - that's very slow indeed. Or, when measured as current flow down a 100 meter piece of 10 base-T cable, it's an astonishingly slow 4.1 km/hour - no faster than a walking person. Even lightning only appears to propogate through then atmosphere at around 1/5 the speed of light. Hope this helps <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

emperor_of_localgroup · Mar 15, 2005

it cant be as fast as speed of light. If i remember the numbers correctly free electrons can have speed of the order of ~10^6 m/sec, whereas light is 3x10^8 m/sec. electrons in conductors will be much slower. 10BaseT speed cant be a correct measure of speed of electricity, because 0 and 1, not constant current, travel through 10baseT cable. <div class="Discussion_UserSignature"> Earth is Boring </div>

yevaud · Mar 15, 2005

Let's say you put 50mV differential voltage, which is almost a standard limit, on 100m of "10Base-T" cable, which is commonly used for LAN wiring. The electric field that is put on a conductor is 0.25mV/m. Average moving velocity of free electrons is only 1.15m per second, which is 4.1km per hour, and it's about the same as walking speed of human. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

pizzaguy · Mar 15, 2005

How fast is electricity? I have limited time to answer, but LOVE your question! If you are asking about simple DC current - like from a battery, then the answers given so far are both right AND wrong. Let me explain... The individual electrons flow at (as far as I can remember) at the speeds given by the poster(s) above me. Rather slow, indeed. But ELECTRICITY moves very fast. Let's say you have a battery and one mile of wire on it, with a light bulb on the other end, and another mile of wire from the buld leading back to the battery. You close the switch, and the electrons are 'driven' by the EMF in the battery. From one pole of the battery, they are repelled, or "pushed" down the wire. From the other pole, they are attracted or "sucked" out of the wire. While the electrons themselves DO move slowly, remember that, as electrons move, they repel other electrons in the wire - makeing them move along. It is THIS effect that moves very fast. So the movement of electrons around the wire is an effect that moves VERY FAST, close to the speed of light. But the actual electron FLOW is very slow. Did I explain that in a way that makes sense? <img src="/images/icons/crazy.gif" /> You can actually measure the speed of the flow of the "electricity", but I have no idea how they measured the speed of the electrons themselves! <div class="Discussion_UserSignature"> Note to Dr. Henry: The testosterone shots are working! </div>

yevaud · Mar 15, 2005

Beats me how they did it. I just remember the article in Physics Review, was back when. PG's exactly correct. Picture a long line of baseballs, all in a row. If you push slowly on one end, the velocity isn't great, on the one hand. However, because the baseballs are all lined up in a row (mind you, this is a very loose analogy), the baseball at the far end suddenly moves. So electrons move slowly in a dense medium, but the overall effect is near light-speed. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

pizzaguy · Mar 15, 2005

That's what I was trying to say ... I really DO understand electronics and RF, but sure cant explain it very well. One thing, in most conductors, the electron flow is certainly slow - but the "ball" on the far end "feels" the push at between .62 and .98 of light speed. What I am saying is, the "push" moves fast - but the 'balls' themselves move slow. I can prove it! As can any RF guy. ( I really only know two subjects really well: How electricity/RF works and how to raise teenagers.) <div class="Discussion_UserSignature"> Note to Dr. Henry: The testosterone shots are working! </div>

yevaud · Mar 15, 2005

Hmm. Well, I was a radar tech. once, but you've got me beat on the teenager bit. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

Saiph · Mar 15, 2005

well, if you use electricity on teenagers....nah, wouldn't work. Basically the electricy is a disturbance in the wire, and travels as a pulse (a type of wave). This wave travels much faster than the medium, as is usually the case (especially with water waves not immediately next to the shore). Anybody know how fast the wave propagates in a superconductor? <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

yevaud · Mar 15, 2005

Hmm. Let's see...no resistance on the one hand, but there's still an intervening medium... Err...good question. Have to think about that one... <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

vogon13 · Mar 15, 2005

Suspect for the case of DC, superconductivity would allow leading edge of waveform to propagate at the speed of light since the interaction between the electrons is electromagnetic (for those of us with advanced college degrees, that was a clue, yuck yuck.) For an AC waveform in a superconductor, there may be interactions of suceeding waveforms with each other, but then we are looking at a dissipating system and ..... on second thought, AC propogates at SOL also. <img src="/images/icons/laugh.gif" /><img src="/images/icons/laugh.gif" /><img src="/images/icons/laugh.gif" /><img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

pizzaguy · Mar 15, 2005

Hmmm. I agree that superconductors could propagate the wave at light speed. But the speed of the individual electrons would not change, would they? (I think you guys are gonna make my head hurt soon...) <div class="Discussion_UserSignature"> Note to Dr. Henry: The testosterone shots are working! </div>

yevaud · Mar 15, 2005

I think that's what Saiph was saying. Under normal conditions, resistance of the medium would cause the electron flow to slow down. But under superconduction, with the activity of the individual atoms slowed down so much... The problem is, most superconducters work at well above absolute zero, so there will still be activity on the atomic/subatomic level. So I don't know... <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

siarad · Mar 16, 2005

To put it in perspective of your usage, namely your PC, it travels about one tenth the speed of light. The capacity & inductance affect this. The speed of travel is also affected by the amount of power transmitted. The old ISA bus & the SCSI bus transmit high power requiring terminating resistors to consume this. The PCI bus in the PC relies on low power & sends a half voltage down the line which meets an open circuit & like a brick wall reflects the wave back upon itself doubling the voltage which wave travelling back produces the information action. Although apparently slower the lower power allows an actual higher speed. Further the more information per second i.e. higher frequency causes the electricity to concentrate more & more towards the edge of the conductor. A circular conductor is preferred & in some printed circuit board a thicker copper is used to make the width of track equal to the thickness as the information travel in the thinest part when not circular. Electrons move faster than holes which is why electron transmission is preferred in transistors but other factors may prefer the use of holes even with the speed limitation. The slow travel of holes (Hole storage) in the amplifiers feeding a CRT TV cause letterbox dragging or smudging of objects towards the right. The sharpest edge being the initial one caused by fast electrons even with special hole removal circuitry. Reality is more complex than at first thought & the above is a very simplistic view

yevaud · Mar 16, 2005

He asked for a simple answer, not a dissertation. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

pizzaguy · Mar 16, 2005

To put it in perspective of your usage, namely your PC, it travels about one tenth the speed of light. Care to back that statement up? The PCI bus in the PC relies on low power & sends a half voltage down the line which meets an open circuit & like a brick wall reflects the wave back upon itself doubling the voltage which wave travelling back produces the information action 1) What the hell is a "half voltage"? 2) As for this "doubling the voltage" - care to back THAT up as well? If you are setting up reflections in a digital circuit, aren't you making a mess of the data? Would you not simply design your equipment such that there are NO reflections? Further the more information per second i.e. higher frequency causes the electricity to concentrate more & more towards the edge of the conductor. A circular conductor is preferred & in some printed circuit board a thicker copper is used to make the width of track equal to the thickness as the information travel in the thinest part when not circular. Ah, the "skin effect", no argument there. The slow travel of holes (Hole storage) in the amplifiers feeding a CRT TV cause letterbox dragging or smudging of objects towards the right./i> First, 'hole theory" is stupid. The guy simply asked about how fast electricity (and/or electrons themselves) travel in an electric circuit. Secondly, where the hell did you get this "dragging or smudging of objects toward the right"? I am gonna be gone most of today, will check back when I can... <div class="Discussion_UserSignature"> Note to Dr. Henry: The testosterone shots are working! </div>

zero_cool · Mar 16, 2005

Thanks for clearing that one up pizza guy, and for everyone else thanks for the help anyways, so now i know electricity is almost the speed of light, correct?

Saiph · Mar 16, 2005

well, to be fair, if it isn't the s.o.l. It certainly is a good fraction there-of. Now, the other fun question.. is it "c" or the s.o.l. in the material? <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

pizzaguy · Mar 16, 2005

Thanks for clearing that one up pizza guy, and for everyone else thanks for the help anyways, so now i know electricity is almost the speed of light, correct? It sure is. Let's say you are sending very high frequency ac electricity (also known as RF or radio) thru that old TV twinlead lead-in wire from your TV antenna. The signal, an AC current, moves along the line at .82 to .95 of lightspeed in free space. (The exact number depends on exactly which line you are using, and what kind of web or spacer is used between the wires.) If you switch over to coax cable (RG-6 or RG-59) it will slow to .66 to .79 - depending again on exactly which cable you are using and what dielectric is used in that cable. If you hook a BATTERY up to it, then what the line is made of no longer matters, 'cause DC is simpler. To be honest, I cannot answer for certain, but would certainly think it's VERY CLOSE to lightspeed. But I will stop right there, I'd rather give a partial answer, than an incorrect one. Now, remember, the electrons themselves are moving real slow, but the effect of them 'pushing' on each other travels along the line at the speeds indicated above. (If you apply a voltage at one end, it is 'felt' at the other end at near light speed'.) So we get away with saying that electricity (which is the MOVING of electrons) moves very fast, indeed. Thanks for the question - there are few questions on SDC that I can answer! (There are many questions here that I cannot even understand... <img src="/images/icons/crazy.gif" /> like quantum mechanics, black holes and all this orbital dynamics stuff. ) <div class="Discussion_UserSignature"> Note to Dr. Henry: The testosterone shots are working! </div>

centsworth_II · Mar 16, 2005

"...so now i know electricity is almost the speed of light, correct?" I'll have to go back to: "It depends how you look at it." A common way to describe electric current flowing through a wire is to compare it to water flowing through a pipe -- or a hose. Imagine a 100' long hose attached to a water source. If the hose is empty when the water is turned on and the water rushes along the hose at 10' per second, it will take 10 seconds for the water to appear at the end of the hose. You would say that the water's speed was 10' per second. Now imagine that the hose is full when the water is turned on. The water still travels at 10' per second but it appears at the end of the hose almost immediately. A conducting wire is like the full hose. It is full of electrons. As soon as the switch is turned on, electrons appear at the end of the wire just as water appeared at the end of the full hose as soon as the water was turned on. However the actual speed of electrons (current) in the wire may only be only several feet, or even inches, per second, depending on the resistance of the wire. I guess you could say that the speed of electricity depends on the resistance of the material through which it is moving. Wire, air (lightning), super conductors, all have resistances that allow electrons to move at anywhere from near the speed of light to just a few inches per second. <div class="Discussion_UserSignature"> </div>

pizzaguy · Mar 16, 2005

Imagine a 100' long hose attached to a water source. If the hose is empty when the water is turned on and the water rushes along the hose at 10' per second, it will take 10 seconds for the water to appear at the end of the hose. You would say that the water's speed was 10' per second. Now imagine that the hose is full when the water is turned on. The water still travels at 10' per second but it appears at the end of the hose almost immediately. A conducting wire is like the full hose. It is full of electrons. As soon as the switch is turned on, electrons appear at the end of the wire just as water appeared at the end of the full hose as soon as the water was turned on. However the actual speed of electrons (current) in the wire may only be only several feet, or even inches, per second, depending on the resistance of the wire. You should take a bow after that - I'm gonna save it to disk. (I promise to admit that I found it online.) <img src="/images/icons/smile.gif" /> I guess you could say that the speed of electricity depends on the resistance of the material through which it is moving. Wire, air (lightning), super conductors, all have resistances that allow electrons to move at anywhere from near the speed of light to just a few inches per second. Not so sure I agree. Resistance reduces current flow (the NUMBER of electrons flowing), but I never thought that anyone said that it slowed it down(the SPEED of the flow of the electrons), just that it reduced the quantity of electron flow. Damn, time to hit the books... <div class="Discussion_UserSignature"> Note to Dr. Henry: The testosterone shots are working! </div>

centsworth_II · Mar 17, 2005

"You should take a bow after that..." Thanks, although using flowing water as an analogy for electric current is hardly original. "Not so sure I agree." Very prudent of you. I was going by my own flawed general knowlege, no expertise. I'll let you do the hard research. <div class="Discussion_UserSignature"> </div>

newtonian · Mar 17, 2005

siarad - Yes, please state your source for electon speed. Here is a similar quote: "Material particles (those with mass) can get up close to the speed of light but can never quite reach it. In fact, all the electron can muster when circling the nucleus is about one tenth of the speed of light." - "Awake!," 11/22/79, p. 17. However, that motion may not be orbital despite the fact that electrons are considered in one of a number of possible, actually quite complex, orbitals - i.e. I do not know if orbitals are actually in orbit - but they certainly circle the nucleus - though the shapes can be way more complex than a circle (= sphere in 3 dimensions). Electricity is, as noted, not simply the speed of electrons. Do we have an update from that 25 year old estimate of the speed limit of an electron?

pizzaguy · Mar 17, 2005

Electricity is, as noted, not simply the speed of electrons. Electricity is usually defined as the flow of electrons along a conductor, or the effects of their flow along a conductor , their orbital speed isnt' what is being talked about. <div class="Discussion_UserSignature"> Note to Dr. Henry: The testosterone shots are working! </div>

centsworth_II · Mar 17, 2005

Do we have an update from that 25 year old estimate of the speed limit of an electron? The speed limit of the electron is the universal speed limit: the speed of light. But, like most things in our universe, they don't very often approach that limit. Earthly scientists need to build large expensive accelerators that pump huge amounts of energy into electrons to get them traveling at near the speed of light. The electrons traveling through a home's electrical wires are subject to far lower energies and are traveling much slower: inches per second. I would say that the speed of an electron can be anything from zero to the speed of light depending on its circumstance. <div class="Discussion_UserSignature"> </div>

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