The main aim of this text is two-fold. Firstly, it shows engineers why it is useful to deal with, for example, Hilbert spaces, imbedding theorems, weak convergence, monotone operators, compact sets, when solving real-life technical problems. Secondly, mathematicians will see the importance and necessity of dealing with material anisotropy, inhomogeneity, nonlinearity and complicated geometrical configurations of electrical devices, which are not encountered when solving academic examples with the Laplace operator on square or ball domains. Mathematical and numerical analysis of several important technical problems arising in electrical engineering are offered, such as computation of magnetic and electric field, nonlinear heat conduction and heat radiation, semiconductor equations, Maxwell equations and optimal shape design of electrical devices. The reader is assumed to be familiar with linear algebra, real analysis and basic numerical methods. This volume should be of interest to mathematicians and engineers whose work involves numerical analysis, partial differential equations, mathematical modelling and industrial mathematics, or functional analysis.