Final answer:
It is true that a rubber blank should be used when feeding a wire through a metal body to protect it from abrasion and potential electrical hazards. The use of such protective measures helps to ensure electrical safety and the integrity of the wiring.
Step-by-step explanation:
The correct answer is a) True. When a wire is fed through a metal body, it is essential to use a rubber blank or a protective grommet. This is to prevent the wire from abrasion, which can damage the insulation and potentially expose the conductive material inside. Such exposure increases the risk of electrical shorts and potential shock hazards, especially if the wire becomes compromised enough to make contact with the metal body through which it is fed.
Concerning the supplied information:
- The high-voltage wires that are connected to tall metal-frame towers are indeed held aloft by insulating connectors. These wires are, however, not typically wrapped in insulating material; instead, they are bare, relying on the air and distance from grounded objects to serve as insulation (Answer: b) False).
- In the realm of circuit diagrams, it is not correct to assume that the voltage is the same at every point in a given wire if there are elements such as resistors or other components present in the circuit that can create a voltage drop (Answer: a) False).
- Dropping a bar magnet through a copper tube does induce an electric current in the tube due to Lenz's Law and electromagnetic induction (Answer: b) True).
- If four wires are made from the same material, their resistance will vary depending on their length and thickness. Wire with greater length or smaller cross-sectional area will have higher resistance (Applicable answers depend on the characteristics of the wires provided which are not detailed here).
- Wood is typically an insulator; however, lightning can indeed travel through a tree to reach Earth due to the high voltage that can create a conductive path even through poor conductors (Answer: a) True).