Conventional books on the mechanics of materials treat elastic deformations of solids through one-dimensional models for the extension of rods, torsion of shafts and bending of beams. In functional materials, mechanical, thermal, electric and magnetic fields interact among themselves, and therefore, need a more comprehensive model. This book presents a systematic treatment of the three-dimensional theories for these coupled phenomena and the corresponding one-dimensional models for extension, torsion and bending. This book adopts a mixed approach by devoting the first half of the book to the development of the three-dimensional theories of elastic, thermal, electric and magnetic fields as well as their interactions in dielectrics, conductors and semiconductors. The remainder of the book presents the one-dimensional models for extension, torsion and bending systematically.