Recent content by joao_pimentel

Hi, thank you very much for reference, nevertheless I suppose I won't be able to trace the directions of F at each point. I'll continue searching if I find anything

Can you kindly reference me a good sketch, cause honestly I can't distinguish good form bad sketch, when it concerns magnetic fields.

##F=\nabla (cB \mathbb{.}B)=\nabla (c|B|^2)=c\nabla (|B|^2)=c\sum_{k=1}^3\frac{\partial (|B|^2)}{x_k}\mathbb{\vec{e_k}}=c\sum_{k=1}^3 2 |B|\frac{\partial (|B|)}{x_k}\mathbb{\vec{e_k}}=2c|B|\sum_{k=1}^3 \frac{\partial (|B|)}{x_k}\mathbb{\vec{e_k}}=2c|B|\nabla (|B|)## Considering ##2c|B|## a...

PS: I can see that close to poles, F is higher as m is aligned with B (cross product is maximum) and there is a great change in B, which provokes the gradient to be high in magnitude, but it would be nice to see one picture of the vector F at each point :) Can you give any reference? Thanks in...

So I suppose this is my answer \mathbf{F}=\nabla \left(\mathbf{m}\cdot\mathbf{B}\right) where \mathbf{m} is the vector of the magnetic dipole moment, which has the direction from south pole to north magnetic pole. I suppose as well that \mathbf{B} at each euclidean point is the tangent of all...

sorry. Yes I meant a ferromagnetic material like iron for example. Can you give me any formula or reference? Thank you

Magnetic field of a permanent magnet and respecetive force Hello I just want you to explain me a bit of physics, cause I am a lay. How to relate (which formula) the magnetic field of a permanent magnet, the vector B at each point (x,y,z), with the force applied to a certain particle of...

That's what I can't understand because every time I see images of magnetic field I see this By the way, I know that the force is F=q(E + v\times B) But how to relate the Force created by the magnetic field of a permenant magnet if the ball is stopped, v=0, and there is no Electric field You...

Hello I was patent examiner on the Portuguese patent office for 3 years and we have a lot of perpetua mobile applications, so I wanted to find now, the theoretical misunderstanding I'm missing here Imagine you have a track (on a table, on the xOy plane) on which a metal ball would...

Thank you so very much :)

ok S^1 is compact, i.e., closed and limited and the line would have to be if there were a homeomorphism between both. On the other hand, if I remove a point, I wouldn't have a compact set, on both, but one is still conncted and the other is not. And I suppose, that if one is path...

ok, so we assume that there is a homeomorphism between the unit circle and a closed subset of R, and then as we remove a point, we have a connected path in the circle and we don't have it in the subset of R. But what is the relation between path connectedness and homeomorphism? AHH, ok, the map...

ok, I see that it will not be possible to find a path between any two points in [a,b] \setminus \left \{ c \right \} because there will be a 'hole' in the line I see also that it will be possible for S^{1}\setminus \left \{ p \right \} because it will be possible 'to find a path around'...

Hi, sorry my delay, I've been thinking. If I remove a point from each, we wouldn't have a connected path, I suppose nor it would be a closed interval... @poverlod Thank you very much :) I think I saw it, but still don't get it :) Can't I miss the last point, i.e. can't I make a map without the...

Ok, using what I found in wikipedia, a continuous function f from [0,1] to the circle radius 1 could be f(t)=\left(\sin\left(2\pi t\right), \cos\left(2\pi t\right)\right) \ t \in [0,1] so, I know what you mean (intuitevely) that a circle is always connected, and a line is not, but I don't...