Final answer:
When work is to be done near overhead lines, they must be de-energized or safety measures must be put in place.
Step-by-step explanation:
Physics - High School
When work is to be performed near overhead lines, the lines must be de-energized or other protective measures must be provided before work is started. This is because overhead power lines carry a high voltage and pose a significant risk of electric shock if proper precautions are not taken. De-energizing the lines means turning off the power to ensure there is no electrical current flowing through them, thus eliminating the risk. Alternatively, other protective measures such as insulating barriers or personal protective equipment can be used to protect workers from electrical hazards.