Final answer:
True, a single point of failure in a physical star topology can bring down the entire network. It is false that high-voltage lines are insulated; they are held by insulators but are bare. True, electric-field lines from a positive charge point outward, and false, visible light is not the only radiation capable of causing the photoelectric effect.
Step-by-step explanation:
The statement is true: In a physical star topology, there is a single point of failure which can cause the entire network to go down. In this type of network configuration, all nodes are connected to a central hub. If the central hub fails, none of the nodes can communicate with each other, leading to a network outage.
High-voltage power lines are indeed held aloft by insulating connectors, and it's false that these wires are wrapped in an insulating material. They are typically bare wires because the air provides sufficient insulation and wrapping them would be impractical and costly.
Concerning electric charges, it is true that the electric-field lines from a positive point charge spread out radially and point outward. This is a basic principle of electrostatics.
The statement that visible light is the only type of electromagnetic radiation that can cause the photoelectric effect is false. Ultraviolet light and other forms of electromagnetic radiation that have higher energy than visible light can also cause the photoelectric effect.