1. Defining Electricity and its Major Components Mr. Scheu

2. So what is this mysterious stuff that we call electricity? Electricity surrounds us and for most of us, life without electricity would be totally different. Electricity can be used in a wide variety of ways Electricity surrounds us and for most of us, life without electricity would be totally different. Electricity can be used in a wide variety of ways –For example:  Electric motors turn electricity into motion. (locomotives)  Light bulbs turn electricity into light  Computers turn electricity into information. (this PowerPoint)  TVs turn electricity into moving pictures. (the Young Frankenstein DVD)  Speakers turn electricity into sound waves. (music on your radio)  Toasters, hair dryers and space heaters turn electricity into heat.  X-ray machines turn electricity into X-rays. How would life be without electricity? How would life be without electricity? –we would revert back to fireplaces for heat, wood-fired stoves for cooking, candles for light and the slide rules for computation, and to talk over long distances, we are left with smoke signals and postcards.

3. Objectives Today we will: Today we will: –Define electrical terms –Discuss the components of an electrical circuit –Describe how electrical energy is measured –Define Ohm’s law and illustrate the relationship between voltage, amperage, watts, and ohms of resistance

4. Electricity Basics Electricity— Electricity— –a source of energy that can be converted to light, heat, or power. –A movement of electrons known as electrical current

5. Theories of Current Flow Electron Theory of Current Flow Electron Theory of Current Flow –Belief that electrons flow from a negatively charged atom to a positively charged electrons Conventional Theory of Current Flow Conventional Theory of Current Flow –Theory that current flowed from positively charged atoms to negatively charged atoms Both Theories are still in use today, and it is important to not confuse the two.

6. Electrical Circuits A simple circuit must contain A simple circuit must contain 1)A source of electricity to start the flow of electrons (a battery, etc.) 2)A conductor that the electrons flow through 3)a load or consumer to use the flow of electrons (a light bulb, motor, etc.) –Load—any device that converts electrical energy into another form of useable energy 4)A conductor connected from the load, back to the source Complete vs incomplete circuit source load Wires

7. Generating Electrical Current Where is electricity generated? Where is electricity generated? –Electricity is produced from a generator (example: power plant) –Generator—converts energy from other forms, and causes electrons to flow through the circuit  Examples of converted energy include: –Water –Steam –Wind –Any others?

8. Other types of generators… Storage Batteries (chemical generators): generate electrical current by chemical reactions from chemicals stored inside the batteries Storage Batteries (chemical generators): generate electrical current by chemical reactions from chemicals stored inside the batteries –Wet-cell battery– reaction between the electrodes and the electrolyte solution –Dry-cell battery—electrolyte is a compound in a paste form

9. Other types of generators… Mechanical energy: a magnetic force is used to move electrons; known as electromagnetic induction Mechanical energy: a magnetic force is used to move electrons; known as electromagnetic induction Piezo electricity: electricity that is produced when pressure or force is applied Piezo electricity: electricity that is produced when pressure or force is applied Thermoelectric process: electricity produced by heat energy; the more heat, the more current produced Thermoelectric process: electricity produced by heat energy; the more heat, the more current produced Solar power: uses photocells to generate electrical current Solar power: uses photocells to generate electrical current

11. Journey of Electricity from being generated to use

12. Conductors and Insulators Resistance—tendency of an element or material to prevent electrical flow Resistance—tendency of an element or material to prevent electrical flow Conductors—elements and materials that have low resistance (Gold, Silver, and Copper are good conductors) Conductors—elements and materials that have low resistance (Gold, Silver, and Copper are good conductors) Insulators—elements that do not readily allow electrical current to flow through them (glass, porcelain, cotton, dry wood) Insulators—elements that do not readily allow electrical current to flow through them (glass, porcelain, cotton, dry wood) –Insulating ability may be lost when material becomes wet

13. How Electrical Energy is Measured Electrical current—the flow of electrons through the conductor; measured in amperes (A or amps for short) Electrical current—the flow of electrons through the conductor; measured in amperes (A or amps for short) Amperage—the rate of electrical current flow per second Amperage—the rate of electrical current flow per second Similar to flow of water (gallons per minute) of water pump Similar to flow of water (gallons per minute) of water pump

14. How Electrical Energy is Measured Voltage (V or volt)– potential force that causes current to flow in conductor Voltage (V or volt)– potential force that causes current to flow in conductor Compared to pounds per square inch of pressure in the water pipe Compared to pounds per square inch of pressure in the water pipe Current cannot exist without the pressure of voltage to force it through the conductor Current cannot exist without the pressure of voltage to force it through the conductor

15. How Electrical Energy is Measured Electrons do not flow freely through even the best conductors, just as water must overcome friction of the pipe wall to flow through a pipe Electrons do not flow freely through even the best conductors, just as water must overcome friction of the pipe wall to flow through a pipe Ohm ( Ω )– the unit of measure of the resistance to electrical flow Ohm ( Ω )– the unit of measure of the resistance to electrical flow –Affected by  The elements of which the conductors are made  Length of conductors –The longer the conductor, the greater the resistance to current flow  Cross-sectional area of conductors –The smaller the diameter of the wire, the greater the resistance to flow  Temperature of conductor –The hotter the wire, the more resistance to current flow

16. Relating Voltage, Amperage, and Ohms of Resistance Ohm’s law--the flow of electricity through the conductor is always directly proportional to the voltage it produces Ohm’s law--the flow of electricity through the conductor is always directly proportional to the voltage it produces Volts Amperage X Ohms Amperes= Volts/Ohms Volts= Amperes x Ohms Ohms= Volts/Amperes Ohm’s Law in Triangle expression

17. Example Problems 20 A = 120 V 6 Ohms 120 V = 20 A x 6 Ohms 6 Ohms = 120 V 20 A

18. Relating Voltage, Amperage, and Watts Watt—a measure of electrical power, or the amount of electrical energy the load or consumer uses Watt—a measure of electrical power, or the amount of electrical energy the load or consumer uses The higher the wattage the rating, the faster the electrical energy is being converted The higher the wattage the rating, the faster the electrical energy is being converted Watts Amperage X Voltage Volts= Watts/Amps Watts= Volts x Amps Amps= Watts/Volts Wattage formulas in Triangle Expression

19. Sample Problem: Suppose six large 200-watt bulbs are to be installed in a 120 volt electrical circuit. How many amps must flow when the lights burn at rated wattage? The source of electrical current will supply 120 volts of pressure. Six bulbs will draw 1,200 watts of power or energy (6 x 200 = 1,200 watts). Suppose six large 200-watt bulbs are to be installed in a 120 volt electrical circuit. How many amps must flow when the lights burn at rated wattage? The source of electrical current will supply 120 volts of pressure. Six bulbs will draw 1,200 watts of power or energy (6 x 200 = 1,200 watts).

20. Solution Which formula must we use? Which formula must we use? A=W/V A=W/V (1200 watts/120 volts) = 10 amps (1200 watts/120 volts) = 10 amps

21. Activity Complete the worksheet using the given formulas for calculating amps, volts, ohms and watts Complete the worksheet using the given formulas for calculating amps, volts, ohms and watts

22. Review What is electricity? What is electricity? What are the 3 components of an electrical circuit? What are the 3 components of an electrical circuit? Describe how electrical energy is measured, and what the different terms, such as amps, volts, and ohms mean. Describe how electrical energy is measured, and what the different terms, such as amps, volts, and ohms mean. Tomorrow, we will continue our discussion on electricity as we begin to talk about wiring outlets and light fixtures and other appliances within our homes.