As a practical investigation, I am attempting to measure the magnetic damping of a pendulum with a metal sheet as it swings through a magnetic field. My understanding of the phenomenon conceptually is this:
- As the pendulum swings through the field, the flux through it increases in one direction.
- By Lenz's Law, a current is induced which itself generates a magnetic field to oppose the change in flux.
- The magnetic field from the induced current is attracted to the existing magnetic field, opposing the momentum of the pendulum, eventually slowing it to a stop.
Here is a video example: Demonstration of magnetic dampening of pendulum
With my current set up, I have two solenoids side by side with the same polarity, and a rigid pendulum with a large aluminium sheet able to swing freely between them. With the solenoids on, and a magnetic field definitely being produced by each of the same polarity, I cannot observe any dampening effect.
I am wondering if anyone would have a rough idea of what sort of scale of magnetic field strength I might need in order to have an observable effect with my equipment - a stopwatch to measure the time taken to stop. Also may I have pointers towards estimating what sort of electrical power I would need through my solenoids to produce a certain field strength?