Recent content by aftershock

Homework Statement What are the electric and magnetic fields due to an infinite sheet of surface current \vec{K} = \hat{j}Ko in the plane x=0? The plane is electrically neutral and Ko is a constant. Plane electromagnetic waves are APPROACHING the plane x =0 from either side, incident normally...

I don't think I've seen whatever formula you're using, but I think you're attempting to find the potential inside the sphere. You start from zero since that's you're reference point and integrate up to the surface of the sphere. Then you add another integral since the term you're integrating...

You generally pick a point where the potential is zero. Infinity usually works, but the potential may not go to zero at infinity if the charged object is infinitely large. Think how the electric field does not diminish as you travel away from an infinite charged plane.

This makes sense. Thank you!

Then why can we in this example http://i.imgur.com/9xRkOCM.jpg?1

I've seen an analogous example involving cylinders where my original method works. The only difference is the conductivity is constant. So I think it's not so much the current, but the fact that the conductivity is non constant that I can't use Gauss' Law. Why should that matter though?

I actually did solve it starting from another equation I found in my notes. I'll post what I used later if you're curious but I am on a tablet now and it would be difficult. I am more curious exactly why my original method is incorrect.

I'm not sure I understand the error here. Can you elaborate on that a little?

Homework Statement Two concentric metal shells of radius a and b respectively ( a < b) are separated by weakly conducting material of varying conductivity σ(r) = kr where k is a constant and r is the distance from the common center. If the metal shells are maintained at a constant...

That was directed at the OP, in hopes of him being able to figure out the answer to his question.

What if the box is sliding on the table by itself and there's no friction?

Well what I mean is that coulombs and kilograms don't measure the same thing. Gravity wins in the moon/earth scenario because the mass is so much greater than the charge. That last part compares coulombs and kilograms, right?

Dot4: ha, yeah that's what I meant. Switching them was a typo. Why is it less valid to give the Earth and moon some small charge and then compare the electric and gravitational forces acting between them? You would probably say oh well the mass in this case is so much greater than the...

I hear all the time how the electric force is so much stronger than gravity. I understand both forces are inversely proportional to the distances squared, and that the gravitational constant is roughly 10^20 times greater than the coulomb constant. But one involves charges, while the other...

Homework Statement Homework Equations Frotating = Finertial + Fcor + Fcf The Attempt at a Solution For the inertial field: F = -qv x b -kQq/r2 For the rotating field it would be the same term plus the coriolis and centrifugal forces. The issue I'm having trouble with is this: The v...