Chapter 21 Multi-format Test

Transcription

1 Name: Class: Date: ID: A Chapter 21 Multi-format Test Modified True/False Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true. 1. A series circuit contains branching points and multiple paths for current to flow through. _ 2. Each branch of a parallel circuit has the same voltage. _ 3. Kirchhoff s current law states that all the current entering a branch point must exit the point. _ 4. A kilowatt-hour (kwh) is a unit of power. _ 5. The current from a battery is always direct current (DC). _ Completion Complete each statement. Select the correct term to complete each sentence. There are extra terms in the list. voltage current resistance parallel series breaker zero alternating direct increases decreases stays the same 6. When adding resistance in a circuit, the resistance of wires and batteries are usually given a value of. 7. Short circuits cause the circuit to draw a large amount of. 8. The value of current is the same at all points in a circuit. 9. Each separate resistor in a series circuit creates a(n) drop. 10. The total circuit resistance as more resistors are added in parallel. 11. A circuit in which current has more than one path is called a circuit. 12. A device that protects circuits from high current is a circuit. 13. In the U.S., the electrical system runs on current that reverses 60 times per second which is referred to as current. Matching Match each statement as belonging to either a Series or Parallel circuit. a. Series b. Parallel 14. There are multiple paths for current to travel. 15. There is only one path for current to travel. 1

2 Name: ID: A 16. Current is the same at every point in the circuit. 17. Total battery voltage is equal to the sum of the voltages across each resistor. 18. The voltage across each branch is the same and is equal to the battery voltage. Short Answer 19. The circuit shown below has 3 identical bulbs connected in series to a battery. If 1 bulb is unscrewed, what will happen to the 2 remaining bulbs? 20. Give an example of a circuit that uses alternating current and an example of a circuit that uses direct current. Problem Three resistors, a 2-ohm, a 4-ohm, and a 6-ohm are connected in series to a 6-volt source. Use this information to answer the following questions: 21. What is the total resistance of the resistors in the circuit? 22. Three resistors, each with a resistance of 2 ohms, are connected in series to a 6-volt source. What is the voltage drop across each resistor? 23. A series circuit contains a 9 volt battery and three resistors of 1 ohm, 3 ohms, and 5 ohms. What is the current in the circuit? 2

3 Name: ID: A Three resistors of 1 ohm, 3 ohms and 5 ohms are connected in parallel to a 3-volt source. Use this information to answer the following questions: 24. What is the current through the 3-ohm resistor? 25. Measured in kilowatt-hours, how much energy does a 4,500-watt water heater element use in 2 hours? A radio s label identifies its power rating as 4.0 watts. Assume that the radio is plugged into a 120-volt outlet as you answer the following questions: 26. The power company charges 10 cents per kilowatt-hour of energy. How much would it cost to run this radio for 100 hours? 27. In many homes, 75-watt light bulbs are common. If the bulb is connected to a 120-volt source, what is the resistance to the flow of charge in the bulb? 28. In many homes, 75-watt incandescent light bulbs are common. In one home there are 10 lights, and each light is on 90 hours per month. If the power company charges 15 cents per kilowatt-hour of energy, how much money will be saved each month if all the incandescent bulbs are replaced with 25-watt fluorescent bulbs? Essay 29. In a household parallel circuit, two 100-watt light bulbs operate at 120 volts. If the same bulbs were placed in a series circuit, would the bulbs appear brighter, dimmer, or remain unchanged? In your answer, describe the current through the household circuit and the series circuit. Other The circuit pictured contains 3 identical light bulbs. They are connected to a voltage source which causes 2 amperes of current to flow through each of the bulbs. Figure What is the total resistance of the circuit shown in Figure 21-1? 3

4 ID: A Chapter 21 Multi-format Test Answer Section MODIFIED TRUE/FALSE 1. ANS: F, parallel circuit section ANS: T DIF: basic REF: section ANS: T DIF: basic REF: section ANS: F, energy DIF: intermediate REF: section ANS: T DIF: intermediate REF: section 21.3 COMPLETION 6. ANS: zero 0 7. ANS: current 8. ANS: series 9. ANS: voltage 10. ANS: decreases DIF: basic REF: section ANS: parallel DIF: basic REF: section ANS: breaker DIF: basic REF: section ANS: alternating DIF: basic REF: section 21.3 MATCHING 14. ANS: B section

5 ID: A 15. ANS: A section ANS: A section ANS: A section ANS: B section 21.2 SHORT ANSWER 19. ANS: The other two bulbs will go out when one bulb is unscrewed. 20. ANS: Answers may vary. Correct answers include: Alternating current: household circuits Direct current: battery circuits DIF: intermediate REF: section 21.3 PROBLEM 21. ANS: resistance total = resistance 1 + resistance 2 + resistance 3 resistance total = 2 ohms + 4 ohms + 6 ohms resistance total = 12 ohms DIF: intermediate REF: section ANS: The voltage drop across each resistor in series is part of the total drop. Since each resistor has the same value, the drop across each will be an equal part of the total; voltage total 3 resistors = 6 volts 3 = 2 volts per resistor. DIF: intermediate REF: section ANS: total resistance = 1Ω+3Ω+5Ω = 9 Ω current = voltage resistance current = 9V 9Ω =1amp DIF: intermediate REF: section ANS: current = voltage resistance (or) I = V R; current = 3 volts 3 ohms current = 1 amp DIF: intermediate REF: section

6 ID: A 25. ANS: energy = power time kilowatt-hours = watts 1kilowatt 1,000 watts hours Ê energy = Ê 1kilowatt ˆ Ë Á4,500 wattsˆ Ë Á 1,000 watts 2 hours energy = 9kWh DIF: intermediate REF: section ANS: 12 watts 1kilowatt = kilowatts 1000 watts energy = power time energy = kw 100 hrs energy = 1.2 kwh cost = energy rate cost = 1.2 kwh $0.10/kWh cost = $0.12 DIF: advanced REF: section ANS: power = current voltage (or) P = I V current = power voltage current = 75 watts 120 volts current = amperes resistance = voltage current (or) R = V I resistance = 120 volts amperes resistance = 192 ohms DIF: advanced REF: section

7 ID: A 28. ANS: cost per month = cents/kwh kwh/month; kwh = (watts 1000) hours For each incandescent light: kwh/month = (75 W 1000) 90 hr/month = 6.75 kwh/month cost per month = 15 cents/kwh 6.75 kwh = cents, or $1.01 per bulb. total cost per month = cost per bulb number of bulbs total cost per month = $1.01/bulb 10 bulbs = $ For each fluorescent light: kwh/month = (25 W 1000) 90 hr/month = 2.25 kwh/month cost per month = 15 cents/kwh 2.25 kwh = cents, or $0.34 per bulb. total cost per month = cost per bulb number of bulbs total cost per month = $0.34 /bulb 10 bulbs = $3.40. cost savings per month = cost for incandescent bulbs - cost for fluorescent bulbs cost savings per month = $ $3.40 = $6.70 DIF: advanced REF: section 21.3 ESSAY 29. ANS: The bulbs would appear dimmer. The household circuit is a parallel circuit, and the current flows through one bulb in each branch. In series circuits, the current must flow through two bulbs instead of one. It would draw less current which would be split between two bulbs, resulting in much dimmer light from each bulb. DIF: advanced REF: section 21.1 section 21.2 OTHER 30. ANS: Resistance 1+2 = R 1 R 2 R 1 + R 2 Resistance = R R 3 R R 3 = 1.5 ohms 1.5 ohms 1.5 ohms ohms DIF: advanced REF: section 21.2 = 0.75 ohm 1.5 ohm 0.75 ohm ohm = 0.75 ohm = 0.5 ohm 4

8 Chapter 21 Multi-format Test [Answer Strip] ID: A _ A 16. _ A 17. _ B 18. _ F 1. _ T 2. _ T 3. _ F 4. _ T 5. _ B 14. _ A 15.