1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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...