What is ampacity?

• A. Maximum voltage a conductor can carry
• B. Maximum current a conductor can carry safely
• C. Resistance at room temperature
• D. The color code of insulation

Answer: (B)

Ampacity is the maximum current a conductor can carry safely without its insulation overheating. When electricity flows, heat is generated in the conductor (roughly proportional to I^2R), so the ampacity rating reflects how much current the insulation and surroundings can tolerate without damage. This rating depends on conductor size, material, insulation type and its temperature rating, and installation conditions like ambient temperature and how many conductors share the same raceway. The aim is to prevent insulation damage or fire. It’s not about how much voltage the wire can carry, nor a fixed resistance at room temperature, nor a color code for insulation. To find the right current, you use ampacity charts and apply any necessary temperature or installation adjustments.