Induction heating technology is very much relevant in now a day because of its energy efficiency and user-friendly behaviour. This chapter emphasizes the fundamental concepts regarding the design topologies of the working coil and is supported by a large number of illustrative tables, diagrams and mathematical equations. In this chapter the fundamental principles of induction heating are discussed along with its different components. The utility of induction heated system is also highlighted in detail for different areas. The induction heating phenomenon is very much effective for different industrial applications. Induction heating system is superior to other heating processes. To reduce the skin effect and proximity effect losses, the heating coil is designed by litz wire. However, choice of a litz wire construction is difficult. Computation of AC resistance and inductance of a litz wire is complex. In the present chapters of this book, an attempt is made to design a litz wire for industrial application. This text, written in a clear and lucid manner is useful to understand the basic design of working coil and is a useful reference for design engineers and researchers.