- A. General Materials & Mathematics
- B. Statics
- C. Kinematics & Dynamics
- D. Rotational Mechanics
- E. Gravitation & Astronomy
- F. Fluid Mechanics
- G. Vibrations & Mechanical Waves
- H. Sound
- I. Thermodynamics
- J. Electrostatics & Magnetostatics
- K. Electromagnetic Principles
- L. Geometrical Optics
- M. Wave Optics
- N. Spectra & Color
- O. Vision
- P. Modern Physics
K2-44. Eddy Current Pendulum
To show damping of pendula due to eddy currents.
Eddy current magnet with various pendula.
For an extremely dramatic effect, dip the bob into liquid nitrogen before letting it swing; it stops IMMEDIATELY!
Pendula with bobs of different materials and geometries are swung through the poles of a strong horseshoe magnet. The amount of damping is greater for those bobs in which strong eddy currents can flow. Bobs include, solid copper,copper loop, broken copper loop, laminated copper, copper with central hole, and wood.
Francis X. Hart and Kenneth W. Wood, Eddy current distributions: Their calculation with a spreadsheet and their measurement with a dual dipole antenna probe, AJP 59, 461-467 (1991)