Electricity

1. Electricity • Electricity is a form of energy – Electrical Energy • It cannot be seen, but its effects certainly can in the form of: • Sight • Sound • Feel • Smell

2. Electron Theory • Electron Theory helps explain electricity • The atom is the building block of matter • Different materials have different types of atoms • When electrons move from atom to atom – electricity is “born” • The flow of free electrons is called an electrical current • An electron moving force known as an Electromotive Force (EMF) causes electrons to move

3. Types of Electricity • There are 2 types: • Static – No electron flow – created by rubbing materials together • Dynamic – Electron flow – created using a power source. It can be: • Direct Current (DC) – Flow in one direction – Typically in batteries or • Alternating Current (AC) – Flows back and forth with time – typically in household electricity

4. More on Dynamic Electricity • Current can be: • Direct (DC) flowing always in one direction at any time. • Alternating (AC) which changes direction at regular intervals. How often it changes direction in one second is called its frequency. Frequency is measured in Hertz (Hz) • For example a computer that runs at 2.0 GHz (Giga Hertz) is run by a timing circuit whose current changes direction 2 billion times in one second! • Regular household current is AC and has a frequency of 60 Hz.

5. Types of Materials • Different types of atoms in materials determine how easily electrons flow: • Conductors – • Are materials that conduct electricity • Have loose electrons that move freely • Examples: Copper, iron, most metals, water • Insulators – • Are materials that do NOT conduct electricity • Have tightly bound electrons • Examples: Wood, rubber, most plastics • Semiconductors • Are neither good nor bad conductors • Examples: Carbon, silicon, germanium

6. Conventional current Current – electron flow Electric Circuits Pictorial diagram • Electric circuits have 3 main parts: • A voltage source (for example: a battery) • A conductor to carry the current (for example: wires) • A load: devices that control the flow of current (a light bulb, resistors, transistors, capacitors, etc.). A load has resistance which is its ability to limit the flow of current. Resistance is measured in Ohms. Schematic diagram

7. Terms of Electricity • Voltage – is the electrical pressure that pushes electrons along a conductor • Measured in Volts • Symbol is V • Current - is the flow of electrons • Measured in Amperes or Amps • Symbol is A • Resistance - opposes the flow of electrons like friction • Measured in Ohms • Symbol is Ω

8. Copper wire with free electrons - + Electron Driven on Electron Driven off Electron Movement - - - - - - - - - - - - - - - - - - - - - - - - - - Electricity and the Body The effects of current. • Electricity: • It is the movement of electrons through a conductive material • Electrical current can have dangerous effects on the human body • Extreme care must be used when handling electrical sources and components.

9. Introduction To Electricity Video • Introduction to Electricity and circuits

10. Electronic Components Symbol Picture • Switch: A part that turns on or off the flow of current. It is either open (off) or closed (on). Symbol Picture • Resistor: Designed to limit the flow of current. How well it limits current is measured in ohms. Symbol Picture • Capacitor: It is a device that stores electrical charges. The higher its value the more energy it stores. Blocks DC current and limits the flow of AC current depending on its frequency.

11. Electronic Components Symbol Picture • Inductor (Coil): It opposes changes in current. Lets DC current flow freely, but limits AC current depending on its frequency. Symbol Picture • LED (Light Emitting Diode): • A device that lets electrons flow in one direction and blocks flow in the other. Light Emitting Diodes (LEDs) are special types of diodes that emit light when electrons flow through.

12. Electronic Components • Transistors: Transistors are more or less electronic taps. They control the flow of current on one part of the circuit based on how much current it receives from another. Symbol Picture • Integrated Circuits (ICs, Chips) • An electronic device made up of semiconductor material that contains several electronic components such as resistors, capacitors, diodes and transistors within it. Integrated circuits are used in a variety of devices such as computers, automobiles, audio and video equipment. Symbol Picture

13. Resistors Video • Introduction to Resistors and resistor colour code.

14. Resistor Colour Codes • Resistors are devices that limit the flow of current in a circuit. • For small resistors, values are read using colour codes. • Colours are read from left to right as indicated by the chart on the left. • Here is another example. Can you tell its value? Green Blue Yellow Gold Yellow Violet Orange Silver

15. Measuring Electricity • Voltage, Current and Resistance are measured using a meter. • We use a Digital Multi-meter (DMM) • Settings need to be adjusted depending on the measurement being performed • You must use the correct setting

16. AC Voltage DC Voltage DC Current Resistance Diode Check High Current Only Red Lead Common Ground Meters

17. How are computers made? • How computers are made video