Ill-posed problems of vacuum physical electronics

A major portion of problems related to theory of vacuum electronics have been demonstrated as being ill-posed. As this takes place, only part of ill-posed problems that fall, according to R. Baire, in the 1^st class of analytically expressible functions can be solved by numerical methods. A numerical solution to the remainder of analytically expressible functions that have the only exact solution will considerably differ from the exact solution, no matter how high is the accuracy with which the calculations have been made.