Which of the following is NOT an example of an exposed conductive part?

• A. Metal trunking
• B. Plastic back box
• C. Metal back box
• D. Metal support beams

Answer: (B)

Exposed conductive parts are conductive components that can be touched and may become live under fault conditions, providing a path for fault current. Metal trunking is made of conductive material and is accessible, so it can become live and is an exposed conductive part. A metal back box is also conductive and, if it can be touched, could carry current if insulation fails, so it qualifies as an exposed conductive part. Metal support beams share the same trait: they are conductive and accessible, making them exposed conductive parts as well. A plastic back box, on the other hand, is an insulating material and does not provide a conductive path, so it is not an exposed conductive part.