Answer
See answer.
Work Step by Step
The relay design is shown in the diagram. When a small current flows, it energizes the electromagnet, which is just wire coiled around an iron rod. The electromagnet attracts the piece of iron, which pivots and completes the circuit, letting a very large current flow.
The pivot contains a spring that pushes the piece of iron, so that when the small current stops, the iron piece springs away, and interrupts the large current.
