Electromagnetic mass of an electron

[PainterGuy]

Hi,

I was reading the following Wikipedia article and couldn't make sense of few points. I'd appreciate it if you could help me with it.

Source: https://en.wikipedia.org/wiki/Electromagnetic_mass#Rest_mass_and_energy

Question 1:
What is this "electrostatic energy $E_{em}$"? Is it some kind of electric potential energy? But electrostatic potential energy exists between two charges.

Question 2:
I think "$m_{em}$" is electromagnetic mass of electron at rest. What would be non-electromagnetic mass electron? From the formula it looks like non-electromagnetic mass of electron would be "0".

Question 3:
I don't think the letter "c" in the stands for the speed of light since electron is at rest. It is not stated what "c" is. Could you please comment on it?

Thank you!

 

[hutchphd]

I direct you to the article about classical electron radius before waving my hands rapidly at your questions.

answer1: $E_{em}$ represents the required to assemble a sphere of magnitude one electron charge (thereby overcoming the repulsion). The size of the sphere is chosen to give correct number for the mass.

answer2: from answer1 it is chosen so that $m_{em}= E_{em}/c^2$

answer3: c is light speed

The complete answers here in fact contain $\hbar$ and are therefore quantum mechanical in nature particularly for complete description of the electromagnetic field.

 

[PainterGuy]

Thank you!

If it's electrostatic energy then shouldn't the subscript be "es" in "$E_{em}$"?

 

[weirdoguy]

There are no general rules regarding subscripts. Author decides what he/she wants to use. It does not have to make sense for everyone.