QED Feynman (coupling number called j)

[eb227]

On page 92 (Figure 58) Feynman states:
"The amplitude for a coupling is a number that I will call j; it is about
negative .1 for the electron (this number is sometimes called the "charge").
Charge?? I don't get it.
Would appreciate an explanation?

 

[Meir Achuz]

On page 92 (Figure 58) Feynman states:
"The amplitude for a coupling is a number that I will call j; it is about
negative .1 for the electron (this number is sometimes called the "charge").
Charge?? I don't get it.
Would appreciate an explanation?

In what is called "natural units" in QED, the charge on the electron is given by e^2=1/137, so e would be about .1.
If you want to put in units, you would have e^2/(hbar c)=1/137.
You could even put in 1/fourpiepsilonzero if you want.