Final answer:
Being inside a metal-roofed car during an electrical storm can be safe because the car acts as a Faraday cage. The metal body distributes the electrical charge around the exterior, protecting passengers as long as they avoid contact with metal parts inside. This principle also highlights the dangers of holding metal objects or seeking shelter under trees during storms.
Step-by-step explanation:
During electrical storms, being inside a car with a metal roof is a safe option. This safety is attributed to the car acting as a Faraday cage, effectively creating zero electrical field inside the vehicle. If lightning strikes or an active electrical wire falls onto the car, the electric field's effects remain on the car's exterior, protecting those inside as long as they do not touch any of the metal components of the car's structure.
In essence, the metal roof and body distribute the electric charge around the exterior of the vehicle and then to the ground, preventing the people inside from experiencing the direct effects of the external electrical field. Therefore, the passengers must stay completely inside the car, avoiding any contact with the vehicle's metal parts.
These principles also explain why it is dangerous for a golfer to be holding a metal club during a storm, as it increases the risk of attracting lightning, and taking shelter under a tree is not considered safer due to the potential of a side flash or direct strike.