gravitation and gauss' law

aniketp

hello,
I was wondering if there is an equivalent gauss' law for gravitation like:
[tex]\Phi[/tex]=4[tex]\pi[/tex]G*M_enclosed
any help would be appreciated. Thank you.

Doc Al

Absolutely. See: Gauss' law for gravity

aniketp

thank you. but do magnetic fields have any such law? intuitively, i am inclined to say no,
because magnetic field lines can cross.....but i would like a rigorous proof

Doc Al

Yes, there's a Gauss's law for magnetic fields--it's one of Maxwell's Equations. Since there are no magnetic monopoles, it is rather simple: Gauss' law for magnetism.

Magnetic field lines can cross only where the field is zero.

Defennder

I'm curious as to why there isn't any magnetic monopoles. The freshman physics textbook I read for my intro physics course says that current theory (I think it was Serway) does predict the existence of magnetic monopoles.

Phrak

No one seems to have found any magnetic monopoles. By including magnetic charge and magnetic current terms in Maxwell's equations you postulate magnetic charge. It brings some (anti-) symmetry to the equations, but this is inconsistence with the magnetic potential.