Month: July 2016

130 Damped Oscillation

This video demonstrates both EMI and Oscillations.

Electromagnetic Induction

The oscillating aluminium plate experiences a damping force which is EMI in nature. The aluminium plate cuts the magnetic flux (originating from the neodymium magnets). The induced emf results in induced eddy current in the plate. The induced current interacts with the magnetic field of the neodymium magnets, resulting in F=BIL magnetic forces. The direction of the magnetic forces are always opposite in direction to the (current) velocity of the oscillating plate. How do we know that? Lenz’s Law!


The G-clamp provides a convenient mechanism to gradually increase the amount of damping, thus showing the behaviour of underdamped, critically damped and overdamped oscillations.

An underdamped oscillation always overshoots the equilibrium position and comes to rest only after a number of oscillations.

Critical damping returns the pendulum to rest at the equilibrium position in the shortest amount of time possible, without overshooting the equilibrium position.

An overdamped oscillation does not overshoot the equilibrium position, but takes a longer time before coming to rest at the equilibrium position (compared to critical damping).