Quick Answer: The Baroscope is a physics apparatus that shows the buoyant effect of air. A hollow sphere is balanced against a counterweight on a beam; when air is pumped out of a bell jar around it, the sphere side sinks.
Last updated: October 2026
Key Features
Balance beam with a hollow sphere on one side and a counterweight on the other
Support stand and base
Placed inside a bell jar on a vacuum plate for the demonstration
Shows that air gives an upward thrust to objects
Technical Specifications
Specification
Value
Components
Balance beam, hollow sphere, counterweight, support stand, base
Operation
Manual demonstration with bell jar and suitable vacuum pump
Compatible with
Bell jar, vacuum pump, vacuum plate, rubber vacuum tubing
Main concepts
Air buoyancy, atmospheric pressure, vacuum, density, upthrust
About This Product
In normal air the beam is set to balance, with both sides receiving an upthrust from the surrounding air. Removing the air reduces that buoyant force and the hollow sphere side moves down, which makes the invisible effect of air easy for students to see and links it to density and atmospheric pressure.
Frequently Asked Questions
Why does the hollow sphere side go down in a vacuum?
The buoyant force of air is reduced when air is removed, so the hollow sphere side becomes heavier and the beam tips towards it.
