Data Sheet
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53. LED Light Bulbs
Build the circuit as shown on the left and turn on the switch
(62). Press the press switch (61) and you will light up the
heart LED (69) and the star LED (70) at the same time.
LED-based light bulbs are increasingly being used instead of
traditional light bulbs these days. One reason is because good-
quality LED bulbs can have a useful life of 25,000 hours or
more. This means they can last more than 25 times longer
than traditional light bulbs. That is a life of more than three
years if run 24 hours a day, seven days a week.
54. Hearing Range
Build the circuit as shown on the left and turn on the switch
(62). Press the press switch (61) or touch the reed switch
(83) with the magnet (7) and you will hear the alarm (78)
sound.
The alarm (78) is producing a tone somewhere in the range
of 20Hz to 20kHz, which is the typical range of hearing for
human beings, though specic individual hearing may vary.
Hertz (Hz) is a unit of measurement for frequency. One Hz
represents one cycle per second.
1st level
1st level
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