Download Chapter 20 Electricity

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Chapter 20 Electricity
Multiple Choice (2 pts each)
Identify the letter of the choice that best completes the statement or answers the question.Flash.
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1. If an atom loses electrons, it becomes a
A. negatively charged ion.
C. neutral atom.
B. positively charged ion.
D. neutral ion.
2. The strength of an electric field depends on the
A. amount of charge that produced the field.
B. distance from the charge.
C. amount of charge on a test charge placed in the field.
D. both A and B
3. What is the SI unit of electric charge?
A. ampere
C. volt
B. ohm
D. coulomb
4. Walking across a carpet is an example of charge being transferred by
A. contact.
C. static electricity.
B. induction.
D. friction.
5. If a neutral metal comb is held near an object with a negative charge, the comb will become charged by
A. induction.
C. friction.
B. contact.
D. static discharge.
6. What type of current is used in a battery?
A. parallel current
C. direct current
B. alternating current
D. potential current
7. The type of current in your home is mostly
A. direct current.
C. series current.
B. alternating current.
D. produced by batteries.
8. Which of the following materials allows charges to flow easily?
A. glass
C. an electrical conductor
B. wood
D. an electrical insulator
9. Which of the following would reduce the resistance of a metal wire?
A. increasing its thickness
C. increasing its length
B. increasing its temperature
D. all of the above
____ 10. What is the difference in electrical potential energy between two places in an electric field?
A. current
C. potential difference
B. resistance
D. induction
____ 11. How many paths through which charge can flow would be shown in a circuit diagram of a series circuit?
A. one
C. none
B. two
D. an unlimited number
____ 12. Most of the circuits in your home are
A. series circuits.
C. reversible circuits.
B. parallel circuits.
D. closed circuits.
____ 13. What is the unit of electric power?
A. ampere
B. volt
C. watt
D. ohm
____ 14. Which of the following provides electrical safety?
A. circuit breaker
C. ground-fault circuit interrupter
B. fuse
D. all of the above
____ 15. Information sent as patterns and codes in the controlled flow of electrons through a circuit is a(an)
A. electronic signal.
C. analog signal.
B. digital signal.
D. integrated signal.
____ 16. Electronic signals that are smoothly varying signals produced by continuously changing the voltage or current in a
circuit are
A. digital signals.
C. diode signals.
B. cathode rays.
D. analog signals.
____ 17. A vacuum tube can be used to
A. change alternating current into direct current.
B. increase the strength of a signal.
C. turn a current on or off.
D. all of the above
____ 18. Which of the following is made from a crystalline solid that conducts a current only under certain circumstances?
A. vacuum tube
C. analog devise
B. cathode-ray tube
D. semiconductor
____ 19. A solid-state component with three layers of semiconductors is a(an)
A. transistor.
C. vacuum tube.
B. diode.
D. integrated circuit.
____ 20. A thin slice of silicon that contains many solid-state components is a(an)
A. transistor.
C. diode.
B. integrated circuit.
D. cathode-ray tube.
Completion (2 pts each)
Complete each sentence or statement.
21. The electric field around a positive charge points _________________________ the charge.
22. Electric force is ____________________ proportional to the amount of charge and ____________________
proportional to the square of the distance between the charges.
23. The SI unit of electric current is the ____________________.
24. Wood, plastic, and rubber are good electrical ____________________, and copper is a good electrical
____________________.
25. The SI unit of resistance is the ____________________.
26. A material that has almost zero resistance when it is cooled to low temperatures is a(an)
_________________________.
27. A complete path through which charge can flow is an electric ____________________.
28. A(An) ____________________ signal encodes information as a string of 1’s and 0’s.
29. A cathode-ray tube is a type of ____________________ tube.
30. A solid-state component that combines an n-type and a p-type semiconductor is a(an) ____________________.
Short Answer (2 pts each)
31. What are three ways that a charge can be transferred?
32. What is the difference between direct current and alternating current?
33. Explain why metal wire coated with plastic is used in electric circuits (a complete answer will explain both the
wire and the coating).
34. Electric current is used for different purposes. Compare the use of electric current by a computer and by a toaster.
35. How do fuses and circuit breakers function to help make electrical energy safe to use65?
Figure 20-1
36. Compare the resistance in the three circuits shown in Figure 20-1 when the switches are closed. Explain the cause
of any differences.
37. Explain why the filaments in the light bulbs become hotter than the connecting wires in Figure 20-1.
38. When the switches are closed in Figure 20-1, in which circuit will the bulbs be the brightest? the dimmest?
Assume that all of the light bulbs and batteries are identical. Explain your answer.
Figure 20-2
39. Are both circuits in Figure 20-2 series circuits? Explain your answer.
40. In fig 20-2, assume the resistance sources are light bulbs. Based on the circuit diagrams, what would happen if
one of the bulbs in Circuit A burned out? What would happen if one of the bulbs in Circuit B burned out? Explain
your answers.
Essay (4 pts each) Answers must be in well-written, paragraph form. Electra.
41. How are friction, induction, and static discharge involved in walking across a carpeted floor and shocking
yourself on a metal doorknob?
42. Describe semiconductors, and n-type and p-type semiconductors. Explain the flow of electrons in p-type
semiconductors and why it looks like positive charges flow.
Problem (3pts ea) All work must be shown to get full credit!
43. In an electrical field, the resistance is 2.34 ohms and the current is 4.00 amps. What is the voltage?
44. Jack has created an electrical circuit using wire, a 9.0 volt battery and a light bulb with a resistance of 1.88 ohms.
He wants to increase the current in the circuit by 2.0 amps and decides to change light bulbs. What would the
resistance of the new light bulb need to be to reach his goal? (Ignore the resistance of the wire.)
45. Kelsey is using a circular saw to add a deck onto the back of her house. The saw is using about 12 amps of
current and has a power rating of 1440 watts. What voltage does the saw need?
46. Which would raise your parents’ electric bill more: baking cookies for 1hour 45 minutes in an oven that uses 8200
watts of power or drying your clothes for 2 and a half hrs in a dryer using 5400 watts? (Hint: the electric
company charges a fixed amount for every kilowatt-hr used in a household.) Don’t worry about sig fig’s on this
one!
47. Bonus (4 points)
An electric circuit consists of a 9.0 volt battery, three light bulbs with a resistance of 1.5 ohms each, a switch, and
wire. Two of the light bulbs are connected in series with the third being in a circuit parallel to the first two. Draw
a circuit diagram of this setup. What is the current across the single bulb? The two bulbs in series?
Can you name the super hero that wears a lightning bolt on the front of his outfit? Who was his mother?