Keep it simple please, I am just a 10th grader aspiring to become like you guys and solve complex equations but as of now I came across the chapter current and it said that current is opposite to the flow of electrons and the charge of current is unknown but if all the electrons are flowing in on...

I have a problem with a particular kind of exercise. The question is: Consider $\phi^4$-theory with $\mathcal{L}_\text{int}=-\frac{\lambda}{4!}\phi^4$. Give the symmetry factors of the diagram and prove it using Wick contractions. My attempt for the symmetry factor is: A factor $2$ for the lef...