Recent content by Vegeta

Then how can you find the B field for example from a current carying wire, by using the differential form of Ampére's law, With the integral form you simply get, that the field-strength from a fixed distance r, is (by symmetry) \oint \vec B \cdot d\vec l=\mu_0 I B\oint dl = B2\pi r =...

1. I know there will an induced emf, but you can't work with that by using the differentialform of Faradays, you need the integral form, because you have a flux-change and not a B-field change. 2. Yes I was referring to that when the B-field is constant in space. How do you use Ampére's law...

That sounds reasonable. While I was thinking about the second equation another question arised. When you have Faraday's law in it's differentialform, you only have the time derivatime of B, and not the magnetic flux, so does this mean that the differentialform can ONLY be used if you are...

Hi I have a hard time understanding what the curl really means in Maxwell's equations, for example in a steady-state you have \nabla\times \textbf{E} = 0 and in a time-varying field you have \nabla\times \textbf{E} = -\frac{\partial \textbf{B}}{\partial t} The meaning of the...

Thanks, I think I understand now. Because curl(J(x')) is like a derivative to J(x'), and since J doesn't depend on x, as you both said, then the "derivative" of J with respect to x must be 0. Btw how long will it be, before the LaTeX will be working?

Ohh now I see why StatusX said "Actually, that's not correct either.", that's because in post 5 I wrote \textbf{A}\times (-\nabla f) = \nabla f \times\textbf{A} = \nabla\times(f\textbf{A}) - \nabla f\times\textbf{A} Hehe that makes no sense, it was a typing error. What I meant was...

O yeah that correct I can't just do such operations as in my first post. But when I use that like \textbf{A}\times (-\nabla f) = \nabla f \times\textbf{A} = \nabla\times(f\textbf{A}) - \nabla f\times\textbf{A} = \nabla\times(f\textbf{A}) + \textbf{A} \times\nabla f Is that correct? And...

Thanks, I think I understand it now. But what about my 2. question. Am I correct on that statement?

These Q's are probably simple for those of you who have/completed a course in Vector Calculus. But I'm only a higschool/secondaryschool student, so I haven't. 1. I'm not sure how the infinitisemal magnetic flux density d\textbf{B} from a wire element d\textbf{l} with a current I, which is...

I have about Maxwell's equations and electromagnetic waves. I'm looking for experiments related to this subject. I only found this (Hertz' experiment), http://www.juliantrubin.com/bigten/hertzexperiment.html But that is not detailed enough, my (high school/secondary school) teacher says, that...

I've calculated the efficiency of the Stirling cycle like \eta=\frac{R(T_H-T_L)\ln\left(V_2/V_1\right)}{RT_H\ln\left(V_2/V_1\right)+C_{mV}(T_H-T_L)} Where V_2>1. It's also derived http://www.pha.jhu.edu/~broholm/l39/node5.html" . But my ("Highschool", or secondary school) teacher says...

So by showing that C_V = \frac{\partial U}{\partial T} Holds for constant preassure and constant volume, it is argument enough to say that it most hold, even if both of those thermodynamic variables p and V changes? That is for an adiabatic process.

Ahh ok now I see. Then for constant preassure, \frac{\partial U}{\partial T} = -p\,\frac{\partial V}{\partial T}+C_p And because C_p = C_V + nR and that p\,\frac{\partial V}{\partial T}=nR (is the last expression correct?), then \frac{\partial U}{\partial T} = -p\,\frac{\partial...

Oh, and by the way, I want to know, because I want to prove p V^\gamma , so I can't use this as you say.

I'm familiar with all the things you said. So I don't think that answers my question, which is why can the change in internal energy be expressed like \Delta U = \int^{T_f}_{T_i} C_V \,dT by using the heat kapacitet for constant volume C_V. In another forum, a guy says, that because...