ANSWElizabethR: Yardsagnetic flux are well-defined: ?
M???B·dA, the area integral of the magnetic field. If the integral is over a closed surface, the flux is zero; this is the famous situation which tells you that there are no point sources (called magnetic monopoles) of magnetic fields like there are for electric fields. If you like, you may interpret this as a number, but that is not really fundamental. If you talk about uniform magnetic fields which are perpendicular to a plane surface, ?M=BA , is the flux through an area A. Then, if you interpret ?M as a number, you would simply say, for example, there were 10 lines through an area of 1 m 2 if the magnetic field is 10 T. E???E · dA . This is perhaps a little easier to understand because you can have point charges. For example, if you have a 1 C point charge, the electric field 1 m from it is E=Q/(4 ??0r 2 )=1/(4x3.14x8.85x10 -12 x1 2 )=9.27x10 9 N/C. The flux at a distance of 1 m from the charge would therefore be ?E =EA= 9.27x10 9 x4x3.14x 1 2 =1.17x10 11 Nm 2 /C. Incidentally, this is the flux regardless of where you measure it because the area of the sphere (4 ?r 2 ) surrounding the point charge appears both in the denominator of the field and in the numerator of the flux and cancels. Hence, you could say that there were 1.17x10 11 lines of electric field emanating from a 1 C point charge. You can see this from Gauss's law, ?
