Purpose: designed for middle school physics teaching to understand and study the basic structure and working principle of electromagnetic relays. Structure: the product is composed of two main parts: the electromagnetic system and the contact system. The electromagnetic system includes an electromagnetic coil and an iron core armature. The contact system includes a pair of normally open and normally closed contacts. Principle: when the coil is energized, the iron core generates magnetism, the armature is pulled in, and when the coil power is removed, the iron core loses magnetism and the armature resets, thereby controlling the connected circuit. How to use: it operates with a 9V DC power supply, and can be paired with other controlled instruments (such as indicator lights or demonstration motors) for classroom demonstration. Key benefits: Enables handson understanding of how electromagnetic relays control circuits. Clear visualization of coil energization and armature movement with visible contact changes (normally open vs normally closed). Compatible with common teaching aids and small demonstration devices for versatile classroom demonstrations. Use scenarios: Classroom demonstration of relay operation: power the coil to see the armature move and the contacts switch states. Comparative study: observe the behavior of normally open versus normally closed contacts during energization and deenergization. Project or science fair demonstrations: integrate with indicator lights or small motors to illustrate practical switching and control concepts.