ELECTRICAL SYSTEMS

1. ELECTRICAL SYSTEMS

2. ELECTRICITY STANDARDS 5.1 Measure and calculate voltage, current, resistance, and power consumption in series and parallel circuits, using the appropriate instrument. 5.2 Components of a circuit, including sources, conductors, circuit breakers, fuses, controllers, and loads. Examples of some controllers are switches, relays, diodes, and variable resistors. 5.3 Relationships among voltage, current, and resistance in a simple circuit, using Ohm’s law. 5.4 Resistance is affected by external factors. (e.g., temperature of conductor, length of conductor, cross-sectional area of conductor and material of the conductor). 5.5 Compare and contrast alternating current (AC) and direct current (DC), and give examples of each.

3. Four Parts to an Electrical Circuit Power Source Provide the force (EMF) to cause electrons to move. A battery, Generator, Photovoltaic Cells, Thermocouples Conductor Provides a path for the electrons to flow through the circuit. Copper is formed into wires, bars or channels. Load The part of the circuit that changes the energy of moving electrons into some other useful form of energy. Lights, Motors, Heating elements are examples. Control Regulates the flow of electrons in a circuit. Switches, potentiometers, thermostats, transistors are just some examples.

4. Schematic Diagrams A standard way to represent electrical components using graphic symbols. Closed Switch (On Position) Open Switch (Off Position) Lamp (incandescent) Battery Ground i.e. Earth Resistor AC Generator Potentiometer Draw a schematic for a flashlight.

5. Schematic Diagrams A standard way to represent electrical components using graphic symbols. Fuse Transformer Capacitor Diode Circuit Breaker LED Light Emitting Diode Solenoid Use on Doorbell Relay Switch In a blue print of a house a GFCI is represented with a schematic like the one on the left GFCI Outlet - GFCI Ground Fault Circuit Interrupter

6. Proton Electron Neutron Parts of the Atom • Is positively charged and located in the nucleus • An atom has three parts. • Has no charge and is located in the nucleus • Is negatively charged and is located in the electron cloud and orbits the nucleus. There are the same number of protons (positive charge) as electrons (negative charge) in a balanced atom.

7. Creating Free Electrons and Positive Ions • When two electrons with like charges get close they repel one another. The atom that is missing an electron is now a Positive Ion A Free Electron is formed and will randomly drift in the material.

8. Insulators and Conductors • Conductors are noted for having many free electrons. Metals such as copper, aluminum, gold have many free electrons and are used in many electrical applications. • Insulators will have few free electrons as the atoms in these materials have a strong attraction between the electrons and protons Materials such as rubber, glass, ceramics, and most plastics.

9. Measuring Devices • Voltmeter- Measures volts or electrical pressure • Ohm Meter- measures resistance to electron flow • Ammeter – measures current or the speed at which electrons flow.

10. Series Circuits • Provide only one path for electrons to flow. Electrons flow from negative to positive. The negative charged electrons are repelled from the negative terminal and attracted to the positive terminal. If one light bulb goes out……. they all go out because the path is open. When a circuit is closed the electrons pass through the conductor to each of the loads and back to the power source.

11. Parallel Circuits • A circuit in which the loads are connect on different branches. Me Too! Me Too! Branches distribute the electricity down different paths. I’m a branch Me Too! If one light bulb goes out …... there is still a path for the electrons to flow through the circuit so none of the others will go out.

12. L3 L5 L3 L5 L1 L2 L4 L1 L2 L4 Combinations of series and parallel circuits • When a circuit is wired in series/parallel only parts of a circuit may be effected when a light fails. If lamp L1 burns out, which lamps will remain on and which will go out? If lamp L1 burns out all the other lamps, L2, L3, L4, and L5 will also go out because the path of the electrons has been open. If lamp L3 burns out, which lamps will remain on and which will go out? Houses are wire in a series/parallel with several branches with multiple outlets, lights ceiling fans on each branch. Only lamp L2 and L3 will be out the rest will remain on.

13. Combinations of series and parallel circuits Most circuits in a house are series/parallel. Each branch is is in series with the circuit breaker. Each light or outlet is in parallel with other items on the branch. Even if one device stops working, the others will still work.

14. Ohm’s Law • V= Voltage • I= Amperage • R= Resistance

15. V I x R Ohms Law - Putting the 3 together Ohm’s Law is a basic law about electricity. It shows the mathematical relationship between Electromotive Force or Voltage (E or V) Current (I) and Resistance (R) Current = Voltage/Resistance This simple memory device may be used. Place your finger Voltage = Current x Resistance over the unknown quantity Resistance = Voltage/Current and the math equation will A current is 3 amps and a resistance is 40  What is the voltage? be be displayed A battery supplies 6 volts and the resistance is 12 ohms. What is the current? Voltage = Current x Resistance Current=Volts/Resistance 3amps x 40 = 120Volts 6volts/12 = .5amps

16. V I x R Ohm’s Law Practice 1. A circuit has an applied voltage of 100 volts and a resistance of 1000. What is the current flowing in the circuit? 1st List what you know and don’t know. 4th step show answer 2nd Show Formula 3rd Show Math 5th Label Answer I=V/R I=.1 Amps V = 100 v I = ? R = 1000Ω I = 100V/1000Ω

17. V Ohm’s Law Practice I x R 2. A circuit has an applied voltage of 3 volts and a current flow of .5amps. What is the resistance required? V = 3 v I = 0.5 amps R = ? R= 6 Ω R=3v/0.5amps R=V/I 3. A circuit has an a current flow of 15amps with an appliance that has 8  of resistance. What is the applied voltage? V = ? I = 15 amps R = 8 Ω V = 15 amps x 8 Ω V= I x R V=120 volts

18. Volts 0 Time DC Direct Current • Current that is produced in a circuit by a steady voltage source. Direct current is when electrons flow in one direction in a circuit only. • http://www.walter-fendt.de/ph14e/electricmotor.htm In direct current the voltage will go to maximum or PEAK (almost) instantly so on a graph it looks like this.  Electrons flow from – to + 1 sec

19. Volts 0 Time Draw this graph on your paper Draw this graph on your paper AC Alternating Current • Current that is produced by a voltage source that changes polarity, or alternates, with time. In alternating current the voltage goes to PEAK positively then reverses to zero, the current then goes to PEAK in the negative. When the electrons have gone once in each direction makes cycle and is represented with a sine wave as seen in the graph. http://www.walter-fendt.de/ph14e/generator_e.htm

20. Electrical Power • The rate at which electrical energy is delivered is POWER. Power is also the rate at which an electrical circuit does the work to convert the energy of moving electrons into some other form of energy. • The unit of measure for Power is the watt. The letter symbol for Power is P. The watt is based on on the unit of work, joules per second. 100 watts light bulb uses 100 watts in one hour or 100 watt-hours. If the 100 watts light bulb uses 100 watts in one hour after ten hours the bulb has used 1000 watt-hours or 1 Kilowatt-hour.

21. P E x I Or V The Power Formula The formula is P = E x I • We can calculate the power used by an appliance or item. Power is equal to the Electromotive Force (voltage) multiplied by the current. Using the same technique as the Ohm’s Law Memory device. To solve the problems at the Right. An appliance is rated for 120 volts and draws 10 amps. What is the power used in one hour? Formula: P = E x I P = 120 volts x 10 amps Math: P = 1200 watts Answer:

22. Questions • 15. What is the power used of a circuit that has 120 volts and a current of 12 amps? • A. 12 watts • B. 12 volts • C. 1440 watts • 0.1 volts V = 30 v I = 12 amps P=IE P= 12 amps x 120 volts P= 1440 watts R = ? P= ? The correct answers is _____ C.

23. Questions • 16. If a speaker is rated for 8 Ω and it has 0.25 amps of current flowing to it then what is the Electromotive force at the speaker? • A. .5 watts • B. 1 watts • C. 2 watts • 16 watts V = ? I = 0.25 amps V = IR V=0.25amps x 8 Ω V= 2 volts R = 8 Ω P= ? P= IE P= 0.25 amps x 2 volts P= 0.5 watts A. The correct answers is _____

24. Electrical Safety Fuses have an internal wire that burns out if a current is too great. House Fuse Car fuses In-line fuse Holder and fuse

25. Electrical Safety Circuit breakers which will shut off the circuit if the current flows to much. Electrical Panel

26. A relay Switch Transformer One circuit is used to control a second circuit. When Magnet coil is turned on it will attract the steel plate and move the switch closer turning on that circuit. The primary coil in a Transformer produces a magnetic field that will influence the electrons in the second coil and current will flow. Used to step-up or step down voltage.

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28. Just as in this example there is the potential to move 1000 Gallons of water from the upper tank to the lower tank. 1000 gallons Potential Difference or Voltage • Potential difference is electrical potential or the difference in voltage between two points. • A battery is rated by the number of volts it has or the potential difference it has between the positive and negative terminals at full charge. • Potential Difference is measured in Volts • Potential Difference letter symbol is either V or sometimes E • Anytime there is a difference in voltage between two objects (terminals) there is Potential Difference.

29. MasterCard Visa American Express Discover + + + The Law of Charges Repel Repel • Like charges Attract • Unlike charges Attract It should be noted that an area of influence (an electrical field) exists around each charge. Objects do not have to touch to repel or attract.

30. 60 pounds per square inch Electromotive force would be equal to the pounds per square inch (PSI) that is the force of the water going through the pipe. Electromotive Force • Electromotive force is the amount of push or force that is in the wires pushing the electrons. • Electromotive Force or EMF unit of measure is the Volts • Electromotive force Letter symbol is either V or sometimes E • Electromotive force only exists when electricity is flowing.

31. Gallons per Minute Current would be like the number of gallons per minute are passing a point in the pipe. Electrical Current • Current is the number of electrons to pass at one point in one second. It is the flow of electrons. • Current unit of measure is the Amperes or Amps.  Currents Letter symbol is an I

32. The valve and pipe walls restricts the flow of water Resistance is the friction from the valve and the sides of the pipe. The length of the conductor (wire) will have an effect on the current. The shortest extension cord should be used when using machines. Resistance • Resistance is opposition to current flow. • Resistance unit of measure is the Ohm or the omega symbol . • The letter symbol is an R

33. Power Source Load Conductor Series Circuits Only One Path Here there are two light bulbs in series. What is missing? Control – Control is by disconnecting a terminal anywhere in the circuit or remove a lamp.

34. Parallel Circuits A parallel circuit has more than one path each charge can follow. Disconnecting a lamp terminal or removing a lamp would only stop one of the two lamps.

35. Electrical Safety Correct wiring is not enough to prevent electrical accidents. Most household circuits usually have an average voltage of 120 volts. Each device that is turned on increases the current. If the current exceeds the circuit’s safety limit, the wire may overheat.

36. Questions • 17. If one light on a string of holiday lights burns out and the rest do not the string is wired? • A. In series • B. In parallel • C. With a fuse. • D. In combination. B. The correct answer is _____

37. Questions • 18. Current that flows in one direction? • A. Is AC and supplied by a battery • B. Is AC and is supplied by a generator • C. Is DC and is supplied by a generator • D. Is DC and supplied by a battery. D. The correct answer is _____

38. Questions • 19. A house is typically wired in? • A. Series • B. Parallel • C. Series/Parallel • D. The dark C. The correct answer is _____

39. Questions • 20. AC current that has 60 hertz is typical in USA. This means that? • A. The voltage is at a peak usable 60 volts. • B. The cycles per second are at 60 times a second • C. The watts will never exceed 60 watts • D. The amperes going into a residential home is 60 amps B. The correct answer is _____ End of slide show

40. Current

41. Electromagnetic fields around a live wire Compass influenced by current Electromagnets and Solenoids How electromagnets work How speakers work Electromagnetic induction How generators work Electrical Current and Magnetic fields