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This
experiment uses a small bicolor LED light on the end of a cord anda base
module that can supply both AC and DC power to the LED. Since LED diodes
only pass current in one direction and this device contains two LED's within
one case, when you apply DC power in one direction it glows constantly
green but when DC power is applied in the opposite direction it glows constantly
red. If AC power is applied then the LED alternates between glowing red
and green based on the oscillating frequency of the AC current. Since AC
power runs at 60 Hz and this is typically too fast for the eye to detect,
we swing the LED cord around in a circle in a darkened room and the flashing
LED becomes EASILY visible to the naked eye as it creates a multicolored
ring of light.
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