Which standards govern electrical diagram symbols?

• A. NEMA and IEC symbols
• B. UL symbols
• C. ANSI symbols
• D. ISO symbols

Answer: (A)

Electrical diagrams rely on a shared vocabulary of symbols so anyone reading the drawing can know exactly what each component is, regardless of who drew it. The standard symbol sets used for these diagrams come from NEMA in North America and the IEC internationally. NEMA covers the conventions common in U.S. and Canadian electrical drawings, while IEC provides the worldwide set of symbols and conventions (with IEC 60617 as a key reference). This combination ensures diagrams are understood across borders and industries, making them interoperable and unambiguous. Safety-only marks from UL address certification rather than the graphic symbols themselves, and while ANSI and ISO exist, the most widely applied references for diagram symbols are NEMA and IEC.