Which distance is the shortest straight-line distance through air between conductors?

• A. Creepage distance
• B. Clearance distance
• C. Ground distance
• D. Air-gap distance

Answer: (B)

In insulation terms, you look at two main ways distance can occur: through air and along a surface. The shortest straight-line distance through air between two conductors is called clearance distance. It measures the direct gap in the air between them, which is crucial for preventing arcing when voltage is present.

Creepage distance, by contrast, is the path along the surface of an insulating material from one conductor to another, and it depends on surface conditions and potential tracking. Ground distance isn’t a standard term for this context, and air-gap distance isn’t the formal term used in most standards, though it’s sometimes heard in informal talk. So the correct term for the minimum straight-line air gap is clearance distance.