Re: Lights in compass?

["Daniel L. MacIsaac" <danmac@physics.purdue.edu>]

Jonathan,

Actually, the boat may be steel, or have significant steel members, have a 
mount over the engine etc.  Usually vehicle compasses are mounted first,
then aligned by adjusting compensating magnets.  The vehicle compass is aligned to an external reference compass or by aligning the vehicle body along a known
bearing and then compensating.

It is (of course) also possible to route wiring such that the net magnetic
field at the compass is zero to fix the electrical problem.

Dan M

Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
Visiting Asst Prof, Purdue Univ;  Adjunct Faculty, Indiana Univ at Kokomo
NEW NET ADDRESSES:  danmac@nau.edu  http://www.phy.nau.edu/~danmac


xJONATHAN GILLIS
> A student brought this up in class yesterday when we were doing Oersted's 
> experiment with wires and compasses to see the magnetic fields created by 
> wires.  He said that he (or his family) has a boat with a compass.  The 
> compass has a light in it so you can see it at night.  He asked if the 
> wire carrying current to the light (and I guess the filament itself) 
> would generate a field that would disrupt the compass.  The question made 
> sense.
>
> Doesthe wire effect the compass?  If not, how is it avoided?  Is it just 
> small enough to ignore?
>
> Thanks in advance for any comments!
>
> Jonathan Gillis
> Enloe High School
> Raleigh, NC
> gillis@avalon.nando.net