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Project #7
OBJECTIVE: To show how a resistor and LED are wired to emit
light.
Build the circuit shown on the left by placing all the parts with a black 1 next
to them on the base grid first. Then, assemble parts marked with a 2.
When you close the slide switch (S1), current flows from the batteries
(B1) through the slide switch, through the resistor (R1), through the
LED (light emitting diode, D1) and back to the battery. The closed slide
switch completes the circuit. The resistor limits the current and
prevents damage to the LED. NEVER PLACE AN LED DIRECTLY
ACROSS THE BATTERY! If no resistor is in the circuit, the battery may
push enough current through the LED to damage the semiconductor
that is used to produce the light. LEDs are used in all types of
electronic equipment to indicate conditions and pass information to the
user of that equipment.
Can you think of something you use everyday that has an LED in it?
Light Emitting Diode
Project #8
OBJECTIVE: To show how electricity can only pass in one
direction through an LED.
Rebuild the circuit used in Project #7 but put the LED (D1) in as shown
on the left.
When you close the slide switch (S1), current should flow from the
batteries (B1) through the resistor and then through the LED. When
current flows through an LED, it lights up. Since the LED is in
backwards, current cannot flow. The LED is like a check valve that lets
current flow in only one direction.
In this project, you changed the direction of current through the LED. An
electronic component that needs to be connected in one direction is
said to have polarity. Other parts like this will be discussed in future
projects. Placing the LED in backwards does not harm it because the
voltage is not large enough to break down this electronic component.
One Direction for LED
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