Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Larger kinetic model to illustrate Boyle's law

Demonstration

This experiment is quite elaborate, but it yields quantitative results. A beam balance 'weighs' the pressure.

Apparatus and materials

Vibration generator

Signal generator

Thread

Aluminium sheet

Beam balance

Rubber sheet

Cylinder, wide, 10 cm diameter

Plastic balls, large

Health & Safety and Technical notes


Apparatus set-up for kinetic model to illustrate Boyle's Law

Read our standard health & safety guidance

Hang a light piston of aluminium sheet by a thread from one side of a beam balance. The thread needs to run through a hole in the floor of the balance.

The piston should fit loosely in a wide vertical cylinder, about 10 cm in diameter.

Fix a rubber sheet over the base of the cylinder and place some large plastic balls, such as those used for electrostatic experiments, into the cylinder.

Adjust the height of vibrator so that its vibrating rod is just a millimeter or two below the rubber sheet.

Procedure


a Balance the beam with the vibrator turned off. 

b Turn on the vibrator - try 50 hertz - and add weights to the balance to measure the force exerted by the bombardment. 

 

Teaching notes


1 If the vibrator and cylinder are raised, halving the volume, you should find that the pressure is doubled. 

2 If, instead, the number of balls is increased, you should find that the pressure increases proportionately. 
 
This experiment was safety-checked in March 2005

 

Related guidance


A simple theory of a gas