1. GRADE 9 ELECTRONICS Introducing Components Developed by Johnny Freese EMDC SOUTH. Adapted by Alistair Mather

2. ELECTRONICS AROUND US Electronic gizmos are all around us. From a radio to a high tech cell phone. They all seem complex and difficult But are all put together with basic electronic components. Electronics begins with understanding these basic components

3. Electronic components 9 V 1,5 V cell battery Cells and batteries store charge. They provide the power for electronic gizmos. South Tech

4. A Basic Circuit An example of a basic circuit: a battery (two 1,5 Volt cells) A switch And a light This light is known as An LED (Light emmiting Diode)

5. LED: Light emmiting diode LEDs emit (give off) light. They are a member of the diode family. Diodes only allow current to flow in one direction. So they need to be connected correctly LEDs are very cheap and last very long Remember: When using more than 3 Volts an LED must be protected by A resistor.

6. A closer look at LEDs Do you see that one leg is longer than the other. Anode The longer leg is the ANODE. It is connected to the positive (+ve) Cathode The shorter leg is the CATHODE. It is connected to the negative (-ve) What do you do if both legs are cut to the same length? Bottom view The flat side of the LED is the CATHODE

7. RESISTORS Resistors determine the amount of current that flows in a circuit. Where there is high resistance, little current will flow. E.g. the buzzer will not be loud Where there is low resistance, a larger current will flow. E.g. the buzzer will be louder

8. The value of resistance Resistors are too small to print numbers on them. A colour code system is used to indicate the value of resistance The resistors that we use most often have four colour bands. Each colour represents a value 1 st band 2 nd band 3 rd band 4 th band 1 st figure 2 nd figure multipliertolerance

9. 4 7 X 10 = 470 Ω

10. LDR: Light Dependant Resistor The LDR is a special kind of resistor. The light sensitive part is the wavy track. As more light falls onto the surface the resistance decreases LDR SYMBOL

11. LDRs have very high resistance. As soon as the light shines the resistance drops dramatically. LDRs can be used in two basic ways: 1.Circuits that need to sense light 2. Circuits that need to sense darkness LDR: Light Dependant Resistor Why do street lights switch on at sunset and off at sunrise ?

12. TRANSISTORS Transistors have two functions: 1.A switch 2.To amplify a signal The shape of transistors may vary but all have three legs: BASE EMITTER COLLECTOR Like magic a small current can be transformed into a large current Like magic a small current can be transformed into a large current

13. TRANSISTOR SYMBOL BASE: Activates the transistor EMITTER: Negative lead COLLECTOR: Positive lead There are two types of transistors, NPN and PNP. The NPN transistors are used most often. Transistors are used in most electronic circuits: Here are some examples: Radios, amplifiers, Alarm circuits and TV sets