Re: What is a milligauss, and how strong is it?

1 milligauss = 10^(-3) Gauss = 0.001 Gauss
1 Gauss = 10^(-4) Tesla = 0.0001 Tesla
1 Tesla = 1 Weber/m^2 = 1 kg/s^2/A

The strength of electromagnetic field is affected
by the sources (currents and charges) and the 
environment. In most cases it is proportional to 
the strength of the sources. For example, if your
magnetic field is generated by a current, then
if you double the strength of the current, the 
strength of your magnetic field will also double.

If you have a long straight wire on which there
is a current of 0.01A (you can use a 1.5V battery
and a 150ohm resistor to generate such a current),
then at a distance of 0.1m from the wire the
strength of the magnetic field is

mu0 * I / (2 * pi * r) N/A^2*A/m
= 4 * pi * 10^(-7) * 0.01 / ( 2 * pi * 0.1) kg*m/s^2/A/m
= 2 * 10^(-8) kg/s^2/A
= 2 * 10^(-8) Tesla
= 2 * 10^(-4) Gauss
= 0.2 milligauss

Therefore, milligauss is quite small a unit for
magnetic field strength. You can easily generate
magnetic field of several milligauss.

The following page contains information about the
units for magnetic field strength.
 http://physics.nist.gov/cuu/
Units/units.html

The following page did some measurement of the
magnetic field near high-voltage transmission
line. The results are in milligauss (mG).
 http://www.vitatech.net/map4.html