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B Electron's drift speed

  1. Jul 20, 2017 #1
    [​IMG] http://imgur.com/a/hFubT
    Fig1.jpg
    [​IMG] http://imgur.com/a/fquuF
    Fig2.jpg

    In the first image, first line in the last paragraph.
    The first sentence define that carriers move with an average velocity component Vd in the x direction(in fact, carriers also move with an average velocity component in the y direction). The second sentence states that the "speed" Vd of the charge carrier along the wire is an average speed called the drift speed(speed is the total distance divided by time, that is, it also include the average component in the y direction).

    I may want to ask that is my interpretation correct?
     
    Last edited by a moderator: Jul 20, 2017
  2. jcsd
  3. Jul 20, 2017 #2
  4. Jul 20, 2017 #3

    davenn

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    what are you defining as the y direction ?

    I don't think so
     
  5. Jul 20, 2017 #4

    davenn

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    Is this homework ?
     
  6. Jul 20, 2017 #5
    No, that's not my homework, I am the physics hobbyist
     
  7. Jul 20, 2017 #6
    The image uploaded on the website is resolution decreased, is there other way to upload?
     
  8. Jul 20, 2017 #7

    davenn

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    OK

    so please answer my earlier question ..... what are you defining as the y direction ?
     
  9. Jul 20, 2017 #8
    vd is the average velocity in x direction. There must be the average velocity in y direction, let's say vy.
     
  10. Jul 20, 2017 #9

    davenn

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    that didnt really answer my Q

    current is along the length of the wire ie. the x direction for DC it is one direction only
    for AC it alternates back and forward ... how could it be in any other direction ?
     
  11. Jul 20, 2017 #10
    Sorry, I am in bad English.........
     
  12. Jul 20, 2017 #11

    davenn

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    that's OK :smile:

    did you understand my reply ?
     
  13. Jul 20, 2017 #12
    Although being along with a wire, the electron is actually moving like zigzag motion.
     
  14. Jul 20, 2017 #13

    davenn

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    yes that is correct. BUT that isn't the current flow that is just the standard random motion of the electrons

    When a voltage potential is applied to the wire ( the electrical circuit), that random movement doesn't stop
    rather now the electric field generated causes the electrons to also have a overall movement along the length of the wire
    and THAT is the drift and the current

    Dave
     
  15. Jul 20, 2017 #14
    Thank you!!! I figured it out!!!
    May I ask the other questions further?
     
  16. Jul 20, 2017 #15

    davenn

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    awesome

    just start a new thread for a new topic
    and best to use the B for Basic tag :smile:
     
  17. Jul 20, 2017 #16
    http://imgur.com/a/UXMx3
    In middle paragraph this image."In our structural model, we shall assume that the excess kinetic energy acquired by the electrons in the electric field is lost to conductor in the collision process.

    What is words meaning with red color? as far as conductor is concerned?

    For whole sentence, that is, for those electrons in the collision process whose kinetic energy offered by electric field is dissipating and converting to the heat. right?
     
  18. Jul 20, 2017 #17
    Actually it's the same topic, should I start with a new thread?
     
  19. Jul 20, 2017 #18

    davenn

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    keep it here then :)
     
  20. Jul 20, 2017 #19
    Thank you, I already posted the question :)
     
  21. Jul 20, 2017 #20

    sophiecentaur

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    The Average (i.e. the mean) velocity in the y direction will be zero. The RMS speed in the y direction could be anything, depending on the temperature of the wire because the average Kinetic Energy of electrons corresponds to the temperature.
    The interaction of the free electrons with the lattice of the metal will cause the wire to heat up and the Electrical Energy Lost per Coulomb of charge is the Potential Drop (Volts) across the length of wire. (Joules Per Coulomb is Volts).
     
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