Module 1 Units 3,4,5

Transcription

1 Module 1 Units 3,4,5 1. What is matter? Anything that occupies space or has mass 2. What are the two general categories of substances? Elements and compounds 3. How many naturally occurring elements are there? What is a compound? Material with atoms of more than one type 5. What is the atomic number of an element equal to? Number of protrons in nucleus 6. Which element has an atomic number of 6? Carbon 7. What word means the ability to interact? Valence 8. What force keeps electrons in their orbit around the nucleus? Centrifugal 9. Which electrons have more energy, the ones in a close orbit or far orbit? Far 10. What is the maximum number of electrons in the fourth orbit? What is the maximum number of electrons in the valence orbit? Which electrons are easiest to knock from their orbit? Single one in the outside orbit 13. How many valence electrons do conductors have? What is one insulator that is a gas? helium 15. What makes an element a semiconductor? 4 valence electrons 16. Name some semiconductors. Carbon, silicone, germanium, tin, and lead 17. What is an ion? Atom that has had electrons added to or taken from the orbits 18. Can atoms be made more negative by removing protons? No, it is done by adding electrons 19. What is coulombs law of electrostatic charges? The force between two charges at rest is directly proportional to the product of the magnitude of the charges. It is also inversely proportional to the square of the distance between them. 20. What is the result of doubling the distance between two charges? Force is reduced to ¼

2 21. What is polarity? The charge at one point with respect to another 22. What are the three ways a body may receive a charge? Friction or contact, conduction, or induction 23. What happens when two dissimilar materials are rubbed together? Electrons are transferred from one to the other 24. What happens when a charged material comes into contact with an uncharged material? Some of the charge is transferred to the uncharged body 25. What happens when a negatively charged substance is brought into contact with a positively charged substance? They will both be neutralized 26. Name four practical applications that use an electrostatic charge? Painting, Sandpaper manufacturing, Air filters, and Xerography (Photocopying) 27. What is one environment where an electrostatic charge could be a real hazard? Transferring of explosive fuels 28. How does current flow according to electron theory? Negative to positive 29. What device is used to split atoms? Van de Graaff generator 30. What happens when molecules are broken and recombine to form different molecules? Energy is absorbed or given off 31. What happens to the extra energy given off as a battery moves from a higher energy state to a lower energy state? Given off as electrical energy or emf 32. What is the electrochemical effect? Reversing the discharge reaction by supplying the cell with electrical energy which the cell can store 33. What are two uses of the piezoelectric effect? Electronics (record player needle or microphone) and measuring shifting of plates of land 34. What is the thermoelectric effect? When a junction of two dissimilar metals is heated, a voltage is produced (One metal takes on a negative charge and one a positive) 35. What is one use of a thermocouple? Temperature sensing device 36. What is the photovoltaic effect? When light strikes the surface of some materials they give up this energy to their electrons and they are released causing current to flow

3 37. What is the term used to describe the method generators and alternators use to produce electricity? Magnetoelectric effect 38. Where does all electrical energy come from? Other forms of energy 39. What is one coulomb? Quantity of charge on 6.24 x electrons 40. What is one ampere? One coulomb of charge across a conductor in 1 second 41. What are two other names for voltage? Potential difference and electromotive force 42. What is the term used to describe the potential rise in a circuit? Electromotive force 43. What is the term used to describe the potential drop in a circuit? Voltage drop 44. What is the term used to describe the opposition to the flow of electric current? What is the unit of measurement? Resistance and Ohm 45. What is the formula for finding watts? Watts = E x I (Volts x Amps) 46. What is Ohms Law? I = E/R 47. What is Watts Law? P = E x I 48. What is the resistance of a 750 watt heater on 240 volts? I = P/E = 750/240 = Amps then R = E/I =240/3.125 = 76.8 ohms 49. What is the resistance of a 3000 watt heater on 240 volts? I = P/E = 3000/240 = 12.5 Amps then R = E/I = 240/12.5 = 19.2 ohms 50. How much current would the heater in question 49 draw if connected to 120 volts? I = E/R = 120/19.2 = 6.25 Amps 51. How would you write 20 megavolts to the power of 10? 20 x Write.003 kilowatts as microwatts microwatts 53. Write 200 milliwatts as kilowatts kw 54. Write 10,000 milliwatts as megawatts MW 55. Write 20 megawatts as kilowatts. 20,000 kw

4 56. Write 10 kilowatts as megawatts..01 MW 57. What is the difference between energy and power? Energy is the ability to do work and power is the rate of doing the work 58. What is the unit of measurement for energy? Kilowatt-hour 59. How much energy is used if a 5 KW electric dryer operates for 45 minutes? Energy = Power x Time = 5 x.75 = 3.75 kwh 60. How much energy is used in 30 days if a 10 KW heater operates for 10 hours (Average) in a 24 hour period? Energy = 10 x 10 x 30 = 3,000 kwh 61. How much energy is used if a 30 KW electric furnace operates for 6 hours in a 24 hour period? How much will this cost if the rate is $.08 per kwh? 180 kwh x.08 = $ How much energy is used if a 3000 watt water heater operates for 15 minutes? Energy = 3 (kw) x.25 (hour) =.75 kwh Unit 4 (Short Review of Drawings leading up to Wiring Diagrams) 1. What are the four main types of electrical drawings? Pictorial, block, wiring, and schematic 2. What are the simplest electrical drawings to understand? Pictorial 3. How are components represented in a block diagram? Blocks (Duh!) 4. How are components represented in one-line diagrams? Symbols 5. Which electrical drawings are typically drawn first in the design of a large project? One line diagrams 6. Are circuit conductors shown on a one-line diagram? No 7. Which electrical diagram shows the actual position of components in a system? Wiring diagram 8. Do wiring diagrams show the actual circuit conductors? Yes 9. When wires cross on a wiring diagram, how do we know if they connect at the point of crossing or not? Dot indicates crossing with a connection. No dot indicates crossing with no connection

5 10. What is the purpose of schematic diagrams? Show electrical relationship between components not physical 11. Which type of electrical diagram is a ladder diagram? Schematic Task 2 1. What are the three conditions for current to flow in a circuit? Must have a source, load, and conductors 2. What is the term used to describe a device that changes other types of energy into electrical energy? Source 3. What is the term used to describe a device that changes electrical energy into other types of energy? Load 4. What is an open circuit? Does not form a complete loop and no current flows 5. What is a short circuit? Parallel path of low resistance 6. Where must the switch be placed in a series circuit? Anywhere 7. What is the purpose of a fuse or circuit breaker in a circuit? Protect components from having too much current flow through them 8. What is the meaning of the term polarity? Charge at one point with respect to another 9. What is the direction of current flow outside the source according to our resource? Negative to Positive 10. What type of current changes direction at regular intervals? Alternating Current 11. How many times a second does 60 cycle current change direction? 120 Task 3 1. State Ohm s Law. Current in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance 2. What is the formula for Watt s Law? P = E x I 3. What is electrical energy changed to in a resistive device? Heat 4. What is power? Rate of doing work or rate of energy transfer

6 5. Power is proportional to what two factors? Current and voltage 6. How is the power affected when the voltage is doubled in a given circuit? Power is 4 times as much as the current also doubles. Resistance is fixed and doesn t change. 7. What are I 2 R losses in a circuit? Power lost when current passes through a conductor 8. How is the energy lost in I 2 R losses? Heat 9. What is the voltage in a circuit where 10 amps flows through a 1200W heater? E = P/I = 1200/10 = 120 Volts 10. How much current flows through a 4000W heater connected to 240V? I = P/E = 4000/240 = Amps 11. What is the resistance in the previous question? R = E / I = 240/16.67 = 14.4 ohms Task How should meters be stored in damp and dusty environments? Dust-proof containers with silica gel pack 13. What effect will magnetic fields have on analogue meters? Inaccurate responses or possible damage to the meter 14. Which meter should never be used on a live circuit? Ohmmeter 15. What precaution must be taken when using meters on DC current that isn t necessary when working on AC? Make sure the polarity is correct (Analog) 16. What is parallax error? Error that results from not look straight down on the needle 17. Which meter has a very high resistance, ammeter or voltmeter? Voltmeter 18. How are ammeters connected in a circuit? Series 19. How are voltmeters connected in a circuit? Parallel 20. What is the result of connecting an ammeter in parallel? Short circuit 21. What precautions must be taken when connecting a wattmeter in a circuit? Connect the voltage coil in parallel and don t exceed the rating, connect the

7 ammeter coil in series and don t exceed the rating, don t exceed the watt rating of the meter, and observe correct polarity for both coils 22. What adjustment must be made to an ohmmeter before each use? Zero the meter (Compensate for battery condition) Unit 5 1. What are the two most common sources of power used in the electrical industry? Generators and batteries 2. What are the disadvantages of photovoltaic systems? Produce small amounts of power and it is expensive to produce 3. What is a battery? One or more electrochemical cells 4. What is a cell? Two conductive electrodes of different materials and an electrolyte solution 5. What is a primary cell? Self contained unit that cannot be recharged 6. What is a secondary cell? One capable of being recharged many times by reversing the operating principle 7. What type of cells are the old standard AA, D, and C cells? Carbon-zinc 8. What is the purpose of the vents in secondary cells? Release gasses that are produced during charging and discharging 9. What are the three most common types of secondary cells and what is the cell voltage for each? Lead-acid (Just over 2 volts), nickel-iron (1.2 volts), and nickelcadmium (1.2 Volts) 10. Which secondary cell type is the most rugged and has a long life? Nickel-iron 11. What precautions should be taken around batteries? Lead-acid batteries contain sulphuric acid that is very corrosive Short circuited batteries can explode toxic fumes and gasses are produced when charging and discharging adequate ventilation must be provided and some batteries may produce dangerous voltage levels

8 12. How do photovoltaic cells produce electricity? Photons of light are absorbed by silicone (and some other materials) causing them to release energy. The free electrons are captured and an electric current is produced 13. What are the three main components of a PV system? PV array, DC to AC converter, and battery storage system 14. What are the advantages of PV systems? Clean, durable, and reliable 15. How is most of the electric power used today produced? AC Generators 16. What are some of the methods of turning a generator to produce power? Water, steam, gas or diesel engine 17. What is an alternator? AC generator 18. What is a prime mover? Whatever provides the mechanical energy to turn a generator 19. Which generator is more common today, AC or DC? 20. What is the purpose of a commutator in a DC generator? Convert the generated AC in the machine to DC to supply the load 21. What is the primary application of generator sets? Power important loads during outages 22. End Here (Skip Transformers)