Torsion Balance

Definition

A torsion balance is a sensitive device used to measure small forces, particularly electric and gravitational forces. It consists of a lightweight bar or arm suspended by a thin wire or fiber, allowing the bar to twist or rotate in response to applied forces.

5 Must Know Facts For Your Next Test

1. The torsion balance was used by Henry Cavendish in 1798 to measure the gravitational constant and the mass of the Earth.
2. The torsion balance is extremely sensitive, capable of detecting forces as small as $10^{-11}$ newtons.
3. The period of oscillation of the torsion balance is determined by the torsional constant of the suspending wire or fiber.
4. Torsion balances have been used to measure small electrical forces, such as those between charged particles, as described by Coulomb's law.
5. The sensitivity of the torsion balance is limited by factors such as air currents, temperature changes, and mechanical vibrations.

Review Questions

• Explain how the torsion balance can be used to measure small forces, such as those described by Coulomb's law.
  • The torsion balance is an ideal instrument for measuring small forces, such as the electrostatic forces between charged particles described by Coulomb's law. When two charged objects are placed on the lightweight bar of the torsion balance, the electrostatic force between them causes the bar to twist or rotate. The degree of rotation is proportional to the magnitude of the force, and by measuring this rotation, the force can be calculated. The extreme sensitivity of the torsion balance allows it to detect even the smallest of these electrostatic forces, making it a crucial tool for verifying and studying Coulomb's law.
• Describe the key factors that determine the sensitivity and accuracy of a torsion balance.
  • The sensitivity and accuracy of a torsion balance are influenced by several factors. The torsional constant of the suspending wire or fiber is a critical parameter, as it determines the ease with which the bar can twist or rotate in response to an applied force. Additionally, the mass and moment of inertia of the bar itself play a role, as lighter and more balanced bars will be more responsive to small forces. Environmental factors, such as air currents, temperature changes, and mechanical vibrations, can also introduce noise and interference, limiting the balance's sensitivity. Careful design and isolation of the torsion balance from these external influences are necessary to maximize its precision and reliability in measuring small forces.
• Analyze the historical significance of the torsion balance and its role in the development of our understanding of fundamental physical laws.
  • The torsion balance has played a pivotal role in the advancement of our understanding of fundamental physical laws, particularly in the realm of electromagnetism and gravitation. Henry Cavendish's use of the torsion balance in 1798 to measure the gravitational constant and the mass of the Earth was a landmark achievement that helped solidify our understanding of Newton's law of universal gravitation. Additionally, the torsion balance was instrumental in the experimental verification of Coulomb's law, which describes the electrostatic force between charged particles. By providing a highly sensitive means of measuring these small forces, the torsion balance has been essential in the development and validation of our most fundamental physical theories, making it a crucial tool in the history of science.

Related terms

Coulomb's Law: Coulomb's law is the fundamental principle that describes the electrostatic force between two stationary, electrically charged particles or objects.

Torque: Torque is the rotational force that causes an object to rotate about an axis, fulcrum, or pivot.

Hooke's Law: Hooke's law states that the force required to stretch or compress a spring is proportional to the distance of the stretch or compression.