Final answer:
Larissa needs 600m of wire to cover a 300m distance to the lock and back to create a complete electric circuit. Coaxial cables are used to minimize electromagnetic interference.
Step-by-step explanation:
To understand why Larissa needs 600m of wire for a run to a lock 300 meters away, one should consider the return path for the electrical current. For any electrical circuit to function, it needs a complete circuit, which includes the path to the target and the return path back to the source. In the case of a lock that is 300 meters away, the wire has to extend 300 meters to the lock and then another 300 meters to return, totaling 600 meters of wire. Without this return path, the circuit would not be complete, and the lock would not function.
Additionally, the use of coaxial cables minimizes the electromagnetic field interference with nearby equipment, such as in surveying or audio equipment, by canceling out opposing currents in the different layers of the wire. This is important for long distance transmission where field strength and interference can become a concern.