MadSci Network: Physics

Re: Does a typical running automobile produce a measurable magnetic field?

Date: Tue Jan 27 15:18:48 1998
Posted By: Eric Kramer, post-doc, physics/chemistry, Brandeis University
Area of science: Physics
ID: 885269416.Ph

Absolutely! A car uses electricity for many of it's functions,
and electric currents produce magnetic fields. A car's starter 
motor uses about 100 amps for a couple of seconds (that's what the 
car battery is for) and during normal running it uses a few amps.

You may be able to detect the magnetic fields with
an inexpensive compass. Hold the compass a few feet from 
a parked car while someone starts it. The magnetic field 
should deflect the needle. 
The fields produced by a running car engine are smaller, but 
they should be detectable if you get close enough 
(pop the hood and hold the compass next to the engine. 
If you're young, ONLY try this with the help of an ADULT!). 
Of course, the metal body of the car may have a magnetic field of 
its own, so you'll have to test whether the field changes
when the car is turned off.

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