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Direction of a Magnetic Field for a Current

Discussion in 'Electronic Basics' started by W. Watson, Jan 5, 2006.

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  1. W. Watson

    W. Watson Guest

    I thought the right hand rule applied to determining the direction of B/H.
    One simply wraps their right-hand around the (imaginary) wire wire with
    their thumb aimed in the direction of the current. The fingers curl in the
    proper direction. However, I was looking at a Navy manual on this subject,
    and it shows as below. What am I missing. Does the Navy have a different
    standard for current flow than physicists and EEs?

    ===================
    Magnetic lines of force are indicated by the letter H and are called H
    lines. The direction of the magnetic lines may be determined by use of the
    left-hand rule for a conductor: If you grasp the conductor in your left hand
    with the thumb extended in the direction of the current flow, your fingers
    will point in the direction of the magnetic lines of force.

    Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
    (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
    Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet
     
  2. I can never remember which hand is which (but them, I am a bit
    dyslexic). But I think the right hand rule is used to predict the
    force produced by a current passing through a magnetic field, and the
    left hand rule predicts the field direction around a current.
    http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfor.html
     
  3. John  Larkin

    John Larkin Guest


    The navy uses electron flow, assuming current flows from negative to
    positive, and (almost) everybody else uses conventional-current flow,
    pos to neg. So they have to use the other hand.

    John
     
  4. The right-hand rule is used with conventional current, and the left-hand
    rule with electron flow.

    Cheers!
    Rich
     
  5. W. Watson

    W. Watson Guest

    Thanks. I wonder what the Air Force and Army use? :)


    Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA)
    (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
    Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet
     
  6. John  Larkin

    John Larkin Guest

    I think that all the military schools use electron flow, as do a
    number of trade schools, Heald for sure and many others, I think. It
    confuses the hell out of people when they get out into the real world.


    John
     
  7. Rich Grise

    Rich Grise Guest

    Electron flow, because we're technicians, not academics. ;-)

    Cheers!
    Rich
     
  8. Nah. Thirty-odd years ago the USAF taught electron flow but also
    warned us about "civilian" current. ;>)


    Mark L. Fergerson
     
  9. John  Larkin

    John Larkin Guest

    Were all the ammeters built backwards?

    John
     
  10. Bob Monsen

    Bob Monsen Guest

    So in the navy, current flows from negative to positive voltages? Is that
    why they always draw their schematics upside down?

    --
    Regards,
    Bob Monsen

    "I am turned into a sort of machine for observing facts and grinding
    out conclusions."
    -- Charles Darwin
     
  11. W. Watson

    W. Watson Guest

    Good quote below. (Interesting. It didn't seem to copy into my post.)
     
  12. That's what they do in tubes. The Crookes tube and the CRT are notable
    examples. ;-) So I can't imagine how anything else flows in the wires
    (I know! _CHARGE_ flows!), unless there are little recombinant factories
    at the tube terminals. ;-)

    The bipolar transistor was their saving grace, because they finally got
    hole flow - I can imagine the huge collective sigh of relief when they
    realized, "Ah! Positive current flows in these things! At last!" ;-D ;-D

    But what do you mean "upside down?" Is it just that all of the arrowheads
    are backwards? ;-)

    Cheers!
    Rich
     
  13. John Larkin

    John Larkin Guest

    Positive ions and protons have been moving around for a long time now.

    John
     
  14. Tim Williams

    Tim Williams Guest

    Guess I should tell Rich next time I've got sodium and hydrogen ions buzzing
    around in a pot of Cl- + Na+ dissolved in H2O <--> OH- + H+ solvent. ;-)

    Or any gas discharge (fluorescent lights, thyratrons, etc.), although those
    still use a lot of electrons, owing to the pokey, fat ions used.

    Tim
     
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