What is the difference between electric and electrical and their usage?
For example, what is the difference between “electrical machine” and “electric machine”?
These two words have a large semantic overlap, but at the edges there are a few key differences.
Electric is used to describe things pertaining to electricity. It can also be used metaphorically: “the evening was electric”.
Electrical can be used nearly everywhere that electric is used when pertaining to electricity (aside from some set phrases). It is not generally used metaphorically in the way electric is. The word electrical can also be used in an additional domain: things concerning electricity. So, generally, people do not say “electric engineer” unless the engineer runs on electricity; instead they say “electrical engineer”.
So, in the case of “electric(al) machine” from your question, since you are talking about something that runs on electricity, the two words are essentially identical in meaning.