Final answer:
The statement that amperage should not be changed when welding is false, as different welding conditions require different amounts of current. It is also true that dropping a bar magnet through a copper tube induces an electric current, and high-voltage wires are insulated by connectors.
Step-by-step explanation:
The statement that amperage should not be changed when welding is false. Adjusting the amperage is crucial when welding because different materials and thicknesses require different amounts of current for effective welding. An ammeter, which measures current, should never be connected directly across a voltage source (such as emf) because it is designed to work with low resistance and would present almost a short circuit when placed directly across a high voltage source, potentially causing damage to the meter or creating a safety hazard. Furthermore, appliances and safety devices like fuses and circuit breakers are rated in amperes because the current flow is an important parameter for the proper operation and safety of electrical circuits.
Regarding the related topics in your question:
If you drop a bar magnet through a copper tube, it indeed induces an electric current in the tube due to the changing magnetic field, which is described by Faraday's Law of Electromagnetic Induction, making the statement true.
High-voltage transmission wires are insulated, but not necessarily by being wrapped in material. They are held aloft by insulating connectors to prevent electrical loss and protect structures from high voltage, making the statement true.