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INTRODUCTION

The IEC, the International Electrotechnical Commission, is the authority for world standards in electrical and electronics engineering. The IEC is composed of National Committees in 43 countries formed to represent in international discussions all their national electrical and electronics interests, including manufacturers, users, trade associations, the engineering profession and government. IEC standards, developed by over 200 Technical Committees and Sub-committees whose programmes collectively span electrotechnology, are used as the basis of national rules and standards in over 100 countries, and for the purposes of international trade.

This handbook contains, in a compact and easy-to-read form, the principles governing conventions for electric and magnetic circuits (IEC Publication 375) and the standardization of letter symbols together with a list of letter symbols in general use which have been approved prior to the date of printing this handbook (IEC Publications 27-1, 27-1A, 27-2, 27-2A, 27-2B and 27-3).

Those symbols, constants and units which are taken from ISO (International Organization for Standardization), BIPM (International Bureau of Weights and Measures) or IUPAP (International Union of Pure and Applied Physics) are in line with the latest publications of these organizations.

The terms used are those of the latest editions of the different chapters of the IEV (International Electrotechnical Vocabulary), and especially those of Class 1, dealing with the fundamental concepts.

The list of letter symbols gives the name of the quantity in English and French (as well as the appropriate language in the case of special language editions), followed by the symbol for the quantity and the appropriate SI unit with its symbol, which are the same in all languages, thus indicating the universality of letter symbols and units.

Similarly, the lists of subscripts are bilingual or trilingual, as the case may be.

Alphabetical lists at the back of the handbook contain quantities and qualifying terms (for subscripts) in each language plus a single list of symbols with numerical references, thus independent of the language.