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What is the speed of electricity?

  1. Jun 20, 2005 #1
    What is the speed of electricity?
    How fast does electricity travel?
  2. jcsd
  3. Jun 20, 2005 #2
    I would think it travels at the speed of light, seeing as the electromagnetic force is carried by the photon,which is massless, and travels at the speed of light therefore.
  4. Jun 20, 2005 #3
    If you define electricity as the flow of current, then electricity travels much slower than the speed of light. What you are looking for is drift velocity of electrons through a medium. The speed depends on the amount of current and certain characteristics of the medium it is propogating through.

    http://hyperphysics.phy-astr.gsu.edu/hbase/electric/miccur.html" [Broken] is a nifty little explanation.

    However, the electric field in the wire is established at close to the speed of light (this is the signal sent from your light switch to your light bulb, from example) and electrons closest to the bulb start flowing through the bulb as soon as this field is established.

    I don't really think electricity has a speed :confused:
    Last edited by a moderator: May 2, 2017
  5. Jun 20, 2005 #4


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    Well i think you nailed it when you mentioned drift velocity. I asked one of my professors this last semester because i also figured electricity travels at the speed of light and he was like "nooooooooooo, way slower then that". I thought electricity is electron travel... which has mass...

    Sounds like electricity may be one of those badly-named concepts in relation to electro-magnetic propogation but id unno
  6. Jun 20, 2005 #5
    Yeah, I dont think "electricity" has a speed. Its like saying whats the speed of gravity.
  7. Jun 20, 2005 #6

    I thought that both electricity and gravity have speeds. I think what nitinshetty is asking is how quickly electricity propogates through a material, in the same way that mechanical forces propogate at the speed of sound in the material and gravity propogates at the speed of light i think (I'm not sure if propogate is word I am looking for here).

    For example, If I had a copper wire running from my living room light switch to the sun and I flicked the light switch off would it take 8 minutes before the sun turned off, or much longer, ignoring the time it takes the light to travel from the sun back to me.
  8. Jun 20, 2005 #7


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    It would take quite a long time. It would take however long the signal takes to get to the sun (based on drift velocity i bet) plus the time it takes for light to travel to earth (if we're timing it from your house).

    Whozum, from what im picking up in bits in pieces from around here, there seems to be theories to indicate that gravity is like EM waves or something that actually has a speed.
  9. Jun 20, 2005 #8
    Is it wrong saying gravity (if that's the right word to use) travels at the speed of light as per GR?
    Last edited: Jun 20, 2005
  10. Jun 20, 2005 #9
    I hope not, because that's what I thought it was…
  11. Jun 20, 2005 #10


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    The term 'electricity' is ambiguous.

    Changes in the electromagnetic field propagate at the speed of light in vacuum. On a printed circuit board wire, which is surrounded by dielectric material, changes in the electromagnetic field propagate at about six inches per nanosecond, or about half the speed of light.

    Electrons themselves have thermal velocities on the order of a million m/s, less than one percent of the speed of light. In addition to their random thermal motion, they actually drift from one terminal of a battery to the other at a very slow speed, on the order of centimeters per hour.

    - Warren
  12. Jun 21, 2005 #11


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  13. Jun 21, 2005 #12
    I'm aware, but my point was you made the assumption that I was talking about gravity waves, whereas I could've been a misinformed person and referring to something else, like falling due to gravity, etc.
  14. Jun 21, 2005 #13


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    Per Einsteins GR theory gravitational waves do travel at the speed of light. If a mass such as the sun disappeared the resulting gravity waves would spread out at the speed of light taking 8 mins to reach the earth..
  15. Jun 21, 2005 #14


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    Well, i thought gravity was gravity waves.... i dont know anything :D
  16. Jun 21, 2005 #15
    Yeah no one knows what I'm talking about (which kinda proves my point).

    I'm gonna shut up now.
  17. Jun 23, 2005 #16
    Electricity moves at the speed of light...

    In a superconducting material, electricity is able to move at full speed, the speed of light.

    Answer: No. If you calculate the instantaneous speed of electron
    using the theoretical models, it comes out to be the velocity
    of light. However, we cannot measure instantaneous speeds, but only
    speed averaged over some time scale by measuring position at two
    instants of time. When we do this, the speed is always less than
    the velocity of light. Theoretical models also predict average
    velocity less than speed of light.
    The above discussion only applies to speed of light
    in vacuum. Electrons can , and do, travel at
    speeds faster than
    speed of light in some media.

  18. Jun 23, 2005 #17


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    Since when?

    If you mean "electricity" and the supercurrent, it does NOT flow at the speed of light, thank you. The zero resisitivity is NOT due to it moving at that speed. Rather, it is due to long-range coherence of the condensed cooper-pairs. The gazillion cooper-pairs in this state are all "entangled" to each other, sharing the same state. Nowhere in the formulation - and certainly NOT in the BCS theory - is there anything moving at "full speed, the speed of light".

    And your statement above has no correlation to what you cited from the ANL's Newton's site.

  19. Jun 24, 2005 #18


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    Inside your computer, the manufacturer tries to keep the distances between various circuits (data buses?) as short as possible. This makes for a faster computer.
  20. Jun 24, 2005 #19


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    This would make for an interesting experiment. You could wire some bulbs in series using a very long coil of thin wire and see if there is a measurable time interval between the first and last bulb lighting up.
  21. Jun 24, 2005 #20
    Both Gravity and Electromagnetic interaction have speed. Their speed is the speed of light - the speed of their virtual particles if you like (Graviton and photon respectively). However the speed of current flow is the drift velocity of the electron.

    I think gravity waves are real gravitons - where the gravitational force is mediated by virtual gravitons. Compare this with the electromagnetic force - it is mediated by virtual photons, but the real photons are the ones you actually see.
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