For the wiring, it is important that the students use a 2-way switch. They could use a 3-way or a 4-way, but they need to learn to do the lab per the instructions which asks for a 2-way switch. They need to also make sure that they are using the correct wire colors: black for hot, white for neutral, and green for ground. The switch must be grounded. Also, brass on the light bulb is hot, and silver is neutral.
The light bulb should not turn on after the nick is connected to ground. This is because the electricity takes the path of least resistance, which is the short to ground. Sometimes the 3 amp breaker will trip. This is the circuit breaker that is between the transformer and the circuit breaker box. The 15 amp breaker does not trip, but in a real world application with more voltage and power, it would.
Things that cause a nick in a wire: Sharp edges, vibration, bending, and many others. I accept about anything here as long as the students have some thought.
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