Question

explain why a jar of mixer grinders get hot when the mixer grinder run for a few minutes

Answer 1

that's why because the mixer produces electricity and when the electricity get into the glass it makes it hotter

Answer 2

When mixer grinder starts,its blade starts rotating rapidly .Now, what happens in the process is :-first electrical energy gets converted into Kinetic energy of blade(which provides it the required speed) after that the kinetic energy of the grinder blade gets converted into thermal energy and hence it turns hot.