# Direction of a Magnetic Field for a Current

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

1. ### W. WatsonGuest

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.

(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. ### John PopelishGuest

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 LarkinGuest

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. ### Rich Grise, but drunkGuest

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

Cheers!
Rich

5. ### W. WatsonGuest

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

(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 LarkinGuest

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 GriseGuest

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

Cheers!
Rich

8. ### Mark FergersonGuest

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

Mark L. Fergerson

9. ### John LarkinGuest

Were all the ammeters built backwards?

John

10. ### Bob MonsenGuest

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. WatsonGuest

Good quote below. (Interesting. It didn't seem to copy into my post.)

12. ### Rich Grise, but drunkGuest

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 LarkinGuest

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

John

14. ### Tim WilliamsGuest

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