Book excerpt: Newnes Electrical Pocket Book, Twenty-first Edition, provides engineers with convenient access to various facts, tables, and formulae relating to the particular branch of engineering being dealt with. In the case of electrical engineering, it is essential that the engineer have a clear understanding of the methods by which the various formulae are derived to ensure that any particular formulae is applicable to the conditions being considered. The first section of the Pocket Book is devoted to the theoretical groundwork upon which all the practical applications are based. This covers symbols, fundamentals, electrostatics, and magnetism. Significant space in the various sections is also devoted to clear descriptions of the circuits and principles used in the different types of electrical apparatus. The inclusion of technical descriptions, along with the essential data embodied in the tables, offer the ideal combination for those engineers engaged on the utilization side of the industry, where many different types of equipment and electrical appliances—ranging from semiconductor rectifiers to electrode steam boilers—may have to be specified, installed, and maintained in efficient operation.