If a truck with an uninsulated boom contacts an energized line, through which point will fault current flow?

When a truck with an uninsulated boom contacts an energized line, the fault current will flow through all points of earth contact. This is because the energized line creates a potential difference, allowing current to seek the path of least resistance back to the ground.

The truck itself, considering it is in contact with the ground through its tires (if they are intact and provide insulation), will also conduct a portion of the current. However, if the boom comes in contact with the energized line, it can create a path allowing current to flow through the truck, potentially to the vehicle's frame, and then to the ground through any points of earth contact, such as the vehicle tires or any ground connections.

This phenomenon demonstrates the importance of grounding and the pathways that electricity can take in fault conditions, emphasizing that when dealing with electrical systems, it is crucial to treat all equipment as potentially live and to follow safety precautions to avoid contact with fault current paths.