Purpose: This machine is used for the basic structure and working principle of AC and DC generators in the teaching of junior high school physics and elementary school natural knowledge. Structure: This instrument is a permanent magnet, rotatable armature generator, composed of a stator, a rotor, brushes, a base plate and a manual mechanism. Demonstration content: Demonstrate the working principle of a single-phase AC generator; electric-phase DC generator Great educational toy, it can cultivate children's interest in physics, more intuitive and easy to understand Good for school teaching tool, learning display, and collectibles, also will be a great addition to your lab supplies. Colour:As shown Material:Metal Package Contents: 2 set * Hand crank AC/DC generator Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.