Investigating the Damping of Motion in a Simple Pendulum through Induced Eddy Currents
Investigating the Damping of Motion in a Simple Pendulum through Induced Eddy Currents
Aim:
The aim of my experiment is to determine the different permeances of several metals by measuring the effects of eddy current damping of the motion of a simple pendulum.
Apparatus:
The experiment involved the use of the following equipment:
Electromagnet
Power Supply
Retort Stand w/ Boss & Clamp
3 rectangular pieces of metal, of equal volume. One of Aluminium, Copper, Titanium and Steel.
A Pendulum Arm
An Axle
Two Small Axle Clamps, to hold the Pendulum Arm in place
High Frame Rate Camera
Method:
To determine the effects of the induced eddy currents, I will measure the time taken for the pendulum to halve its maximum angle of deflection. I decided to use a starting angle of 30 degrees, large enough so as to minimise systematic error, but small enough that repeating the experiment wouldn't take excessively long. By connecting a video camera to a computer, I will manually raise the pendulum until the arm is in line with a line marked at 30 degrees from the vertical. I will start recording, and then release the pendulum. Using frame by frame analysis of the video I will determine the frame when the pendulum was released, and the first swing in which the pendulum achieves strictly less than 15 degrees of deflection. By working out the number of frames this takes, and dividing by the frame rate of the camera, I can calculate the time taken. The equipment will be set up as in the diagram on the next page, although the camera is not shown in the diagram. I was careful to ensure that the pendulum's swing was perpendicular to that of the magnetic flux between to the two sides of the electromagnet, so as to maximise the flux linkage.