Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

(A/m) unit explanation

  1. Aug 6, 2012 #1
    hello,
    I can't seem to make sense out of amper/meter....one amp flowing throw a wire with a length of 0.5m would be 2A/m ? how does relate to the magnetic field?
     
  2. jcsd
  3. Aug 6, 2012 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    In a coil, you can find something like "ampere per meter": With a current of 1 Ampere and 100 windings per meter, you get "100 ampere per meter". In a similar way, a cylinder with constant current density (around the interior), can have the property "ampere per meter". And the magnetic field strength inside just depends on this quantity.
     
  4. Aug 7, 2012 #3
    thank you that made it a little bit clearer, but a solenoid has length width height and copper winding length. does m in (A/m) refer to the length of the copper wire?
     
  5. Aug 8, 2012 #4

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    No, it does not. The dimensions are not relevant, as long as the coil is long compared to its other two dimensions (and even if not, it is just a dimensionless prefactor for the geometry). The length of the copper wire is mainly geometry-related. The relevant quantity is the winding density (with unit 1/m), multiplied by the current.
     
  6. Aug 8, 2012 #5
    density can only exist in two or three dimensional space no?!?

    we can have 100 ampere turns in one cubic meter, but in a dimensionless meter??

    you say dimensions are irrelevant, but i can not see how you can have density without dimensions....
     
  7. Aug 8, 2012 #6

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    A 1-dimensional density is nothing mysterious. On a highway, you can have 10 cars per kilometer, for example. "Cars per cubic kilometer" is not a useful quantity.

    If your coil has a length of 2 meters and 100 windings, you have 50 windings per meter.
     
  8. Aug 8, 2012 #7
    ah ok this makes sense now, magnetic field is proportional to the distance and quantity of charge travel per unit time
    thank you for your help
     
  9. Aug 8, 2012 #8

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    hello ctech4285! :smile:

    when i see "A/m", i always read it as "amp-turns per metre" …

    the magnetic field is the amps times the number of turns divided by the length of the solenoid :wink:

    (or the amps times the pitch)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: (A/m) unit explanation
  1. Vacuum explanation (Replies: 4)

Loading...