1. Fruit generator: use lemons, apples, oranges and other fruits to generate electricity and learn the principles of power generation.

2. Paper cup microphone: Use materials such as paper cups and earphone wires to make a simple microphone and understand the principle of signal transmission.

3. Simple wind generator: Use small fans, magnets, coils and other materials to learn the principles of wind power generation.

4. Simple telescope: Use two magnifying lenses and tape and other materials to learn the principles and production methods of telescopes.

5. Simple solar water heater: Use black plastic bags, transparent plastic bags, aluminum foil and other materials to learn the working principle of solar water heaters.