Elenco XP&trade - Manual (Page 22)

Project A17
Build the circuit, but leave the ends of the red and black jumper wires
unconnected at first.
When you place a metal paper clip (not included) across the loose ends
of the jumper wires as shown, current flows from the batteries through
the resistor, through the LED, and back to the battery. The paper clip
completes the circuit and current flows through the LED. Place your
fingers across the terminals and the LED does not light. Your body is
too high of a resistance to allow enough current to flow to light the LED.
If the voltage, which is electrical pressure, was higher, current could be
pushed through your fingers and the LED would light. This detector can
be used to see if materials like plastic, wood, cloth, aluminum, or paper
are a good conductor or a poor conductor.
Conduction Detector
Project A15
Microphone Control
In this circuit, blowing
on the microphone (X1)
changes the LED (D1)
brightness.
The resistance of the
microphone changes
when you blow on it.
You can replace the
microphone with one of
the resistors to see
what resistor value it is
closest to.
Project A16
Adjustable Brightness
In this circuit, changing
the adjustable resistor
(RV) setting changes
the brightness of the
LED (D1).
The lever on RV
adjusts how much
resistive material the
electric current flows
through.
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