Magdeburg Spheres
| Physics: | Vacuums, Air Pressure |
| Grade Range: | Elementary School, Middle School, High School |
| Format: | Hands-on, Stage |
The Magdeburg spheres are a classic demonstration for introducing vacuums and air pressure. They are a fun demonstration for older audiences, especially when you have two strong students try and fail to pull the sphere open!
Materials
- Magdeburg Spheres
- Vacuum Pump
Safety Precautions
Please read the Physical Demonstration section of the Demonstration Safety page before performing this demonstration.
Demonstration
- Presentation (Stage)
- Show the two halves of the Magdeburg sphere, and that they don't stay together well when you press them into each other. Open the valve on the side of the sphere, and hook it up to the vacuum pump.
- Use the vacuum pump to suck the air out of the sphere, and close the valve on the sphere before turning off the pump. Detach the sphere from the pump, and show that you can no longer pull it apart.
- Ask for two volunteers, and have them each take a handle on the Magdeburg sphere. Have them tug at the sphere to try to open it again, but they can't! Take the sphere from them, and then open the valve to let air back inside. It falls right open!
Why This Works
The Magdeburg sphere was first created by Otto von Guericke, and demonstrated publicly in 1654 in Magdeburg, Germany. He developed the sphere as a way to demonstrate how strong Air Pressure can be, which is the pressure we experience from the air around us at all times. By hooking the sphere up to a vacuum pump, we are able to remove almost all of the air inside the sphere, making a Vacuum, or an empty space inside. Since there is nearly no air inside the sphere, and there is a lot of air outside the sphere, the pressure outside the sphere will be much greater than inside. This means that, as hard as anyone tries to pull the two halves apart, the air outside the sphere will push even harder to keep the sphere shut!
Additional Information
- This demonstration pairs well with the Crush The Can and the Marshmallow Smashies demonstrations.
- This demonstration is a part of the Pressure Show