Computerised Cavendish Torsion Balance

The Computerised Cavendish Torsion Balance is an apparatus for demonstrating gravitational forces between two masses. It also enables the gravitational constant to be determined.

The core of the apparatus is a torsion pendulum. Consisting of a light bar with two small lead spheres, the pendulum is suspended horizontally from a thin wire. The tension balance oscillates about a new equilibrium position whenever the large spheres are rotated to a new position.

A capacitive differential sensor measures the rotary motion, removes most noise and vibration components, and the torsion balance outputs the information to a computer. which can then be exported to a spreadsheet.

Results In A Single Lesson

Because of its short oscillation period of 2 - 4 minutes, the torsion balance enables the gravitational period to be determined in a single lesson while having an accuracy of better than 10%.

A Range of Experiment Topics

The torsion balance enables a range of experiment topics to be covered:

• Determining initial equilibrium balance of a torsion pendulum
• Recording of damped oscillations around the final equilibrium position of a torsion pendulum over time
• Determining final equilibrium position of a torsion pendulum by final deflection method
• Determination of gravitational constant G from the period of oscillation and the difference between the equilibrium positions
• Determination of gravitational constant G by acceleration method

Contents of the Computerised Cavendish Torsion Balance

• 1 x Computerised Cavendish Torsion Balance
• 1 x measurement software
• 1 x USB cable

Technical specifications of the Computerised Cavendish Torsion Balance

The technical specifications of the Computerised Cavendish Torsion Balance are:

• Mass of large lead spheres: 1kg
• Mass of small lead spheres: 15g
• Gravitational attraction: <10^-9N
• Torsion wire: Tungsten - 25µm
• Period of oscillation: 2 - 4 minutes
• Angular resolution: 25 microradians
• Sampling rate: 0.5, 1, 2, 5, 10 samples/second
• Dimensions:
  • Length: 190mm
  • Width: 180mm
  • Height: 200mm
• Weight: 5kg