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Science 9: Electricity Unit Review *Know all vocabulary* 1. Identify and describe examples of mechanical, chemical, thermal, and electrical energy. 2. Describe the energy transfers that take place in the following examples: a. Power grids b. Flashlights c. Thermocouples 3. Why are electrodes and electrolytes necessary in a cell? 4. Which electrodes and electrolytes are best for use in a cell? 5. Explain the operation of a St. Louis motor. 6. How does changing the location of the armature, commutator and/or magnets influence the operation of the St. Louis motor? 7. How can knowing the voltage and amperage of an electrical device keep you safe? 8. What is the difference between static and current electricity? List some examples of each. 9. List some examples of electrical conductors and insulators. 10. Which wire conducts electricity the best? The worst? 11. How does electrical resistance influence a polygraph (lie detector) tests? 12. What is a rheostat? 13. How can you use switches and/or resistance to control electrical flow? 14. Use a hydro-flow (water) model to explain current, resistance and voltage. 15. Calculate the resistance in the following examples using Ohm’s law: a. What is the resistance of a light bulb of a 12V battery sends a current of 2.4 A through it? b. A toaster with a resistance of 145 () is connected to a 120 V source. What current will flow through the toaster? c. What is the potential difference across a 1500 () resistor carrying a current of 0.075 A? 16. What are some problems associated with photoelectric cells? 17. What is the difference between a parallel circuit and a series circuit? 18. Which is the best to use when wiring a house, series or parallel? Why? 19. Identify the forms of energy input and output in a system. 20. Calculate the number of watts used in the following examples: a. What is the power (in watts and kilowatts) of a hair dryer that requires 10 A of current to operate on a 120 V circuit? b. The maximum current that a 68.5 cm TV can have is 2A. If the TV is connected to a 120 V circuit, how much power is the TV using? c. A flashlight using 2 1.5 V D-cells contains a bulb that can withstand up to 0.5 A of current. What is the maximum power of the bulb? 21. Calculate cost of electrical usage in the following examples: a. A family uses 3000 kWh of electric energy in a two month period. If the energy costs 11.0 cents per kilowatts hour, what is the electric bill for the period? b. A home-owner finds that she has a total of 42 light bulbs (100 W) in use in her home. If all the bulbs are on for and average of 5 h per day, how many kilowatt hours of electricity will be consumed in a 30 day period? If electricity costs 11 cents per kilowatt hour, how much will these lights cost her? 22. Identify examples of energy dissipation in the form of heat and describe the effect of these losses on useful energy output. 23. Calculate the efficiency (compare inputs and outputs) of the following examples: a. Find the efficiency fo a 23 W fluorescent tube that is used 4.0h per day and in that time produces 66 240 J of useful light energy. b. A 80W incandescent bulb also produces about 66240 J over a 4 h period. What is the efficiency of this light bulb? 24. What are some of the techniques that can be employed to reduce energy consumption in your household? 25. How can you improve the efficiency of some common household devices? 26. Identify and evaluate alternative sources of electrical energy. 27. What are the by-products of electrical generation and describe their impact on the environment? 28. What are some of the issues associated with electrical technologies in storing and transmitting personal information? Science 9: Electricity Vocabulary 1. insulators 2. conductors 3. grounding 4. circuit 5. battery 6. switch 7. resistor 8. loads 9. amperes 10. galvanometer 11. ammeter 12. potential difference 13. voltage 14. volt 15. voltmeter 16. resistance 17. ohm 18. ohmmeter 19. Ohm’s Law 20. series circuit 21. parallel circuit 22. thermocouple 23. thermo-electric generator 24. LED 25. electrochemical cell 26. electrode 27. electrolyte 28. electric generator 29. electromagnet 30. alternating current 31. commutator 32. stator 33. transformer 34. circuit breaker 35. fuse 36. neutral wire 37. hot wire 38. ground wire 39. electrical code 40. transistors 41. power 42. short circuit