How to calculate Electric field analytically on Matlab?

Question

Sebsatien 2012-6-29

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42399-how-to-calculate-electric-field-analytically-on-matlab

回答： Antonio Cedillo Hernandez 2020-4-21

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Greetings!

I need to analytically calculate an Electric field.Here's the equation:

With my very basic knowledge of the software, here's the code:

 if true 
   %function [E]= Etemp(x,y,z,x0,y0,z0,E0,t,c)
    if z<z0,
      E=E0;
    else
      E=-(1./(2*pi))*dblquad('E2(x0,yo)',inf,inf,inf,inf);
      E2=(Rgv/(Rg^2))*((1/c)*z./norm(z)*diftE+((1/Rg)*z./norm(z)*E0));
      clear, 
      syms ro Rg c t;
      f=E0;
      diftE=diff(f,t);  
    end 
end

Beside the feeling of missing something with the code, I have encountered so far a problem with calculating the double indefinite integrals using "dblquad" because it doesn't seems right. Same with using "diff" with indefinte differentials.

I have no experience in this domain and I'm definitely afraid that I'm missing something here (too good to be true. This has to be more complicated then that ). So I'll be eternally grateful for any help.

Thanks very much for any kind of help!

7 个评论
显示 5更早的评论隐藏 5更早的评论

tlawren 2012-6-30

编辑：tlawren 2012-6-30

Do you have an example of E0? It's format will determine how you calculate d/dt[E0]. It might be a good idea to work out the cross products in the integrand, so that you can evaluate each of the field components separately. In the snippet of code you posted, you use the standard multiplication operator (*). Matlab has a cross product function (cross), but you need to look at it's documentation before you use it. I'm not familiar with dblquad, so I can't really say much about it. I can say that using inf for your limits of integration is probably not a good idea. There are probably practical limits you can use, but they will be problem specific. In fact, you might have to run some simulations to determine what good limits will be.

Sebsatien 2012-7-1

编辑：Sebsatien 2012-7-1

The calcuation of E0 is the next level of the work, I'll need another set of equations for calculating fields in a certain point and I'll be looking into it very soon... Thanks of the "cross" tip, I'll need to study its case further. As for dblquad I'm looking into a symbolic way for evaluating integrals, which is more approriate then this operator. Thanks for the help. I'll see what I can do for now

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Walter Roberson 2012-6-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42399-how-to-calculate-electric-field-analytically-on-matlab#answer_52199

Going through what you have written, it appears that your E0 is a numeric matrix. If that is the case, then you cannot do a symbolic differentiation on it. Your f=E0 would be numeric, and diff(f,t) would try to apply the numeric diff() routine (numeric difference between adjacent points) which would promptly complain because the numeric diff() routine cannot accept a symbolic argument for the number of the dimension to operate on.

If E0 is indeed numeric, then diff(sym(f),t) would try to apply the symbolic diff() routine (symbolic differentiation), but since none of the symbolic values would involve the reference variable "t", the differentiation result would be a matrix of symbolic zeros.

3 个评论
显示 1更早的评论隐藏 1更早的评论

tlawren 2012-6-30

编辑：tlawren 2012-6-30

Is the use of infinite limits still a good idea? I'm not familiar with these routines or their underlying algorithms, so I don't know. I've always sought out finite limits (practical infinities) to use instead.

Sebsatien 2012-7-1

Thanks. I suspected as much. I'll look into quadgk and I'll see how to replace the diff with a more convienent operator.

请先登录，再进行评论。

Answer 2

Antonio Cedillo Hernandez 2020-4-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42399-how-to-calculate-electric-field-analytically-on-matlab#answer_427232

Here you have the full MATLAB code explained (in spanish but the first comment is the code): https://www.youtube.com/watch?v=k9srU6aQfL0

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 3

Sebsatien 2012-7-4

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42399-how-to-calculate-electric-field-analytically-on-matlab#answer_52554

Now I'm concentrating in the calculation of the EO, so I searched for equations to calculate the electric field in a point emitted by an electric elementary dipole. Here's the forumla:

So, would I be able to calculate the field using this equation on MATLAB? Is it programmable without eventual problems?

Thanks so much!