Elenco Circuit Maker Sound Plus 200 - Manual (Page 18)

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Project #15
Build the circuit, but leave the ends of the
red and black jumper wires unconnected at
first.
When you place a 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.
Adjustable Brightness
Project #13
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 #14
Conduction Detector
Resistors are used to control or limit the flow of
electricity in a circuit. Higher resistor values reduce the
flow of electricity in a circuit.
In this circuit, the adjustable resistor is used to adjust
the LED brightness, to limit the current so the batteries
last longer, and to protect the LED from being damaged
by the batteries.
What is Resistance? Take your hands and rub them
together very fast. Your hands should feel warm. The
friction between your hands converts your effort into
heat. Resistance is the electrical friction between an
electric current and the material it is flowing through.
The adjustable resistor can be set for as low as 200W,
or as high as 50,000W (50kW).
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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CM-200_Manual_031914.qxp_CM-200_Manual_031914 4/2/14 12:04 PM Page 18