Project 66
Spinning Rings
!
WARNING:
Moving parts. Do not touch the fan or
motor during operation.
Setup:
Cut out the disc on page #52 that looks
like the one shown here. Using Scotch tape,
attach the disc with the printed side up on the top
of the fan blade. Place the blade on the motor as
shown to the left and below.
When the press switch (S2) is pressed, the arcs
will turn into colored rings with a black
background. Notice how the color drops in
brightness when it is stretched to make a
Project 67
Strobe the House Lights
Place the spinning rings under a fluorescent light with a T12 bulb (1.5”
diameter) that runs on normal house current. Start the disc spinning
and release the press switch (S2). As the speed changes you will notice
the white lines first seem to move in one direction then they start
moving in another direction.
This effect is because the lights are blinking 120
times a second and the changing speed of the
motor is acting like a strobe light to catch the
motion at certain speeds. To prove this, try the
same test with a flashlight. The light from a
flashlight is constant and if all other lights are out,
you will not see the effect that looks like a
helicopter blade in a movie. This does not work
with newer fluorescent lights, because they use
an electronic ballast and produce a constant
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