Magnetic Intruder Alert

Learn how the magnet activates the Invader Alarm! A fun construction to discover how a magnetic switch works in the electrical circuit!

HOW IT WORKS: Activate the alarm and close the door. If someone opens the door even a small crack, the alarm will sound. Close the door again or turn off the alarm to stop the buzzer. When the door is closed and the triangles in the magnet holder and the base are aligned, the disc is pulled by the magnet to one side of the hole area. When the door is opened, the magnet moves away from the base and the pull from the magnet is no longer strong enough to hold the disc. The disc rolls down to the bottom of the hole area, and remains between the two plates with the holes. This acts as a switch, completing the circuit and allowing current to flow through the buzzer.