In the thousands of years of inheritance of Chinese culture, all its vastness and profundity are hidden in history, which is reflected in historical materials, mainly including written materials and cultural relics. In our high school history classroom, it is ···

The large magnetic levitation globe utilizes the current magnetic effect to float the globe in mid air. There is a magnet at the top of the globe, and a metal coil inside the circular plastic frame. The metal coil becomes an electromagnet through an electric c···