Chapter 15
  Chapter 15
  1. Diode
  2. LED
  3. Capacitor
  4. Photo Resistor
  5. Circuit Applet
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  This chapter will explain some electrical components in details. After learning their functionalities and properties, you can enjoy building your own circuit!


Section 1: Diode
  Diode rectifies or converts alternating current (AC) to direct current (DC).
diode symbol of diode
(Symbol )

Diode is made of two different parts. One part is called p-type and other part is called n-type. In between, we call it the p-n junction. P-type is silicon mixed with boron, and n-type is silicon mixed with phosphorous. In order to explain how it works, we must know about the octet rule and valence electrons.

The octet rule is that bonded nonmetialic atoms has eight electron outermost shell or energy level. It means that when two chemicals react each other and produce a product, its outer shell has eight electrons.

The valence electrons are the electrons moving aroung the most outer shell of an individual atom and they are often involved into chemical reaction bonding.

Read more about diode.


Section 2: LED (Light Emitting Diode)
  LED is Light Emitting Diode and there are many types of LED. It is made of semiconductors which is related with Gallium and Arsenic. Some can emit light, and some can detect light, and some can even detect radiation. LED is used as light indicators which can be seen in almost every electronic product (such as TV remote controller, sign of computer screen, Num Lock light in keyboard, score board, etc). It works exactly the same as diode, but when electrons jump from n-type to p-type, they lose some energy which is converted to light. Because all the energy is converted to light, LEDs do not consume much energy and can operate at low voltages. They should not be operated at more than 40 mA (miliampere) or 0.04 A (ampere) or 2.2 V (volts). Otherwise, they will blow up.

LED Symbol of LED
(LED and the symbol of LED)

LED emission is visible in the spectrum wavelengths from 0.4 to 0.7m or in the near infrared, which we cannot see, that of wavelengths between 2.0 and 0.7 m. More than 20 billion LEDs are produced each year.


Section 3: Capacitor
  Capacitor is a device that stores the electricity. This device is used to regulate the flow of current. When there is a big drop of voltage, electricty stored by capacitor is released so there is no voltage drop after that. It can also regulate a big increase of voltage.

This device is used in digital circuit such as computer memories. Computer memories can be lost during electric power failure, so the capacitor provides power to maintain information from temporarily loss of power.

A CapacitorSymbol of Capacitor
(Capacitor and its symbol)


Section 4: Photo Resistor
  Photo resistor is normally a insulator, but it becomes a conductor under light. The light gives enough energy to move electron through it.

Photo resistor Symbol of photo resistor
(Photo resistor and its symbol)


Section 5: Circuit Applet
  CircuitYou can build your own circuit here! Refer to Circuit Applet Help for instructions of how to use the Applet.

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