This book highlights the latest advances in research on the thermal plasma of an electric arc discharge between asymmetric electrodes, which were carried out mainly in the Department of Physical Electronics of the Faculty of Radiophysics, Electronics and Computer Systems of Taras Shevchenko National University of Kyiv.The techniques of Optical Emission and Laser Absorption Spectroscopies were predominantly used to investigate the parameters of low-temperature plasma with admixtures of metal vapours. Free-burning electric arcs between asymmetric electrodes fabricated from single-component copper and nickel or composite Ag-Ni materials were used as plasma sources. The experimental techniques were additionally used to examine the erosion properties of studied materials under thermal effect of arc discharges in the indirect way.The book will help readers to familiarize with current research in thermal plasma physics, which was carried out by contributors to promote further implementation into innovations according to public needs. We hope that this issue will be useful and interesting for young scientists or Ph.D. students and mature scientists alike.