I wonder whether a reversible process has to be quasistatic or at least pseudostatic? (probably there exist some processes involving magnetic field which are reversible but not pseudostatic). Below I define what I mean by a reversible, quasistatic and pseudostatic process. Reversible process - let's consider a process R in which initial state of the system was a, initial state of the environment was b and final state of the system and environment was a' and b' appropriately. If there exists a process which changes the state of full system (considered system + environment) form (a',b') to (a,b) the process R is said to be reversible. Pseudostatic process - this is a process during which it may be assumed that both the system and its surroundings maintain thermal equilibrium (the changes are made sufficiently slow). Quasistatic process - this is such a pseudostatic process that in any moment if we slightly change some of the external factors which cause it (pressure, magnetic field, ...) we can reverse its direction. Thanks for any answers.