Recent content by Alettix

Homework Statement For a medium of conductivity ##\sigma##: $$ \nabla^2 \vec{B} = \sigma \mu \mu_0 \frac{\partial \vec{B}}{\partial t} + \mu \mu_0 \epsilon \epsilon_0 \frac{\partial^2 \vec{B}}{\partial^2 t} $$ A long solenoid with ##r=b## has n turns per unit length of superconducting wire anc...

With the approximation that field lines concentrate and that we have a linear medium the question was solved with ampere's only. Thanks for the help!

Yes I have read your previous post, but as expressed in my reply (post #3) I am not convinced by all of it, or rather have further questions. As mentioned in the same post, I have not studied magnetic reluctance and this being a past exam question must be solvable without that concept. Of...

Thank you! I think I am fine with the straight edge gap, what I need help with understanding is what happens in the case with the tapered ends.

Thank you for your answer Charles Link, I am sorry to say it leaves me rather confused. I am doing a basic EM course at University and we have not learned about magnetic reluctance. This being a past exam question, it must be solvable by other means. Do you have any idea how this could be done...

Homework Statement Consider a toroidal electromagnet filled with a magnetic material of large permeability µ. The torus contains a small vacuum gap of length h. Over most of its length the torus has a circular cross section of radius R, but towards the gap the torus is tapered on both of its...

Alright, if I understand it correctly: free charge can only reside on boundaries between ideal insulators and conductors. How then do we deal with non-ideal media, ie. materials which have a low conductivity for instance? Are there any common surface imperfections which could lead to free...

Really? Why? I thought free charges were found on conducting surfaces.

I am not quite sure how it get's there in the first place, but I think that if there is free charge in the system it should be on the boundaries? Like consider the extreme case of a metal-air boundary? Or are the boundary conditions only valid for strictly non conducting media? What if we put...

Homework Statement a) State the boundary conditions for the electric field strength E and electric flux density D at a planar interface separating two media with dielectric constants ε1 and ε2. b) A parallel plate capacitor with a plate separation d is filled with two layers of different...

Fixed it, Thanks a lot for the help everybody!

Yes it would. So angular momentum is assumed to be conserved about the axel only and I must have done a misstake in my algebra when calculating the velocity u.

Oh, I understand thank you! Just out of curiosity: if we disregard gravity completely and only care about the unknown force at the axel (say the windmill is laying horizontal on a table and a rolling ball hits it): would angular momentum be conserved about any point or just the axel where the...

Alrigth, I will check through my algebra!

Can I pretend it is or is it conserved? Is it conserved about all points or just the axel where the external torque is zero?