I have a Ph.D. in physics. To get the degree, I've taken advanced mathematics courses in college and graduate school. In college I've had the basic 4 semester calculus sequence plus a semester of ordinary differential equations and a semester of partial differential equations. Most of electricity and magnetism is merely applied boundary value problems from ODEs. I've also taken mathematical methods courses which went deeply into complex analysis, Greens Functions formulations, Sturm-Liouville theory, hypergeometic functions, and complex analysis. I feel comfortable facing any problem in ODEs or PDEs with little or no preparation. (The same for linear algebra.) For advanced courses in Greens functions, etc., I would need to do a bit of preparation to make most efficacious use of my tutoring contact time.