Physics Chapter 23

13. A circuit breaker often serves the same purpose as a A. capacitor. B. fuse. C. battery D. All of the above choices are correct. E. None of the above choices are correct.

B. fuse

22. Alternating current is normally produced by a A. battery. B. generator. C. both of these D. neither of these

B. generator

18. Stretch a copper wire so that it is thinner and the resistance between its ends A. decreases. B. increases. C. remains unchanged.

B. increases

6. Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry A. more current. B. less current. C. the same current.

B. less current

15. When two lamps are connected in series to a battery, the electrical resistance that the battery senses is A. less than the resistance of either lamp. B. more than the resistance of either lamp. C. none of these

B. more than the resistance of either lamp

16. When a 10-V battery is connected to a resistor, the current in the resistor is 2 A. What is the resistor's value? A. more than 20 ohms B. 2 ohms C. 5 ohms D. 20 ohms E. 10 ohms

C. 5 ohms

28. A 60-W light bulb and a 100-W light bulb are connected in series to a 120 V outlet. Which light bulb has more current in it? A. the 100-W bulb B. the 60-W bulb C. Both have the same current.

C. both have the same current

26. Two lamps, one with a thick filament and one with a thin filament of the same material, are connected in parallel to a battery. The current is A. larger in the lamp with the thin filament. B. the same in both lamps. C. larger in the lamp with the thick filament.

C. larger int he lamp with the thick filament

36. The wattage marked on a lightbulb is not an inherent property of the bulb, but depends on the voltage to which it is connected, usually 110 or 120 V. How many amperes flow through a 70-W bulb connected in a 120-V circuit?

70/120 = .58 A

5. A heater uses 20 A when used in a 110-V line. If electric power costs 10 cents per kilowatt hour, the cost of running the heater for 10 hours is A. $2.20. B. $0.55. C. $0.22. D. $5.50. E. none of these

A. $2.20

21. When a light switch is turned on in a dc circuit, the average speed of electrons in the lamp is A. less than 1 cm/s. B. the speed of light. C. the speed of sound waves in metal. D. 1000 cm/s. E. dependent on how quickly each electron bumps into the next electron.

A. less than 1 cm/s

8. The headlights, radio, and defroster fan in an automobile are connected in A. parallel with a switch for each. B. parallel without separate switches. C. series with a switch for each. D. series without separate switches.

A. parallel with a switch for each

23. There are electrons in the filament of the ac lamp in your bedroom. When you turn on the lamp and it glows, the glowing comes from A. the same electrons. B. the positive charges that flow in the filament. C. different electrons; the ones that flow in the circuit to your lamp.

A. the same electrons

20. In a common dc circuit, electrons move at speeds of A. the speed of a sound wave. B. many centimeters per second. C. the speed of light. D. a fraction of a centimeter per second. E. none of these

D. a fraction of a centimeter per second

19. The source of electrons lighting an incandescent ac light bulb is A. the source voltage. B. electrical outlet. C. the power company. D. atoms in the light bulb filament. E. the wire leading to the lamp.

D. atoms in the light bulb filament

9. A circuit is powered with a battery. Charge flows A. out of the battery and into the circuit. B. only after a couple seconds pass. C. from the negative battery terminal to the positive terminal. D. through both the battery and the rest of the circuit. E. none of these

D. through both the battery and the rest of the circuit

32. What condition must exist between two points in a conductor in order to maintain a flow of charge? A. a switch connected in series B. a high resistance C. a steady magnetic field D. All of the above choices are correct. E. None of the above choices are correct.

E. none of the above choices are correct

30. What is the resistance of a 120-W incandescent lamp connected to a 120-V power supply? A. 60 ohms B. 1 ohm C. 100 ohms D. 144 ohms E. none of these

E. none of these

34. Calculate the current in the 200-Ω filament of a bulb connected to a 140-V line

I = V/R 140/200 = .70 A

4. Calculate the current that moves through your fingers (resistance 600 Ω ) when you touch them to the terminals of a 5.6-V battery.

I = V/R 5.6/600 = 9.3 x 10^-3

35. Calculate the power of a device that carries 0.48 A when impressed with 110 V

Power = I x V .48 x 110 = 53 W

37. The total charge that an automobile battery can supply without being recharged is given in terms of ampere-hours. A typical 12-V battery has a rating of 60 ampere-hours (60 A for 1 h, 30 A for 2 h, and so on). Suppose that you forget to turn the headlights off in your parked automobile. If each of the two headlights draws 2.1 A , how long will it be before your battery is "dead"?

t = 14 horus

2. Rearrange the equation current = voltage/resistance to express resistance in terms of current and voltage. Then solve the following: A certain device in a 170-V circuit has a current rating of 30 A . What is the resistance of the device (how many ohms)?

170/30 = 5.7 ohms

24. In a 110-volt circuit containing a lamp in series with the voltage source A. 110 joules of energy are given up by each coulomb of charge making up the current in the circuit. B. 110 coulombs of charge flow through the lamp every second. C. 110 joules of energy are converted to heat and light in the circuit every second. D. 110 joules of energy are shared among all the coulombs in the circuit at any instant. E. none of the above

A. 110 joules of energy are given up by each coulomb of charge making up the current in the circuit

31. A power line with a resistance of 2 ohms has a current of 80 A in it. The power dissipated in the line is A. 12,800 W. B. 320 W. C. 160 W. d. 40 W. E. none of these

A. 12,800

38. A. Using the formula power = current × voltage, find the current drawn by a 1200-W toaster connected to 160 V . B. Then, using the equation current = voltage/resistance, find the resistance of the toaster.

A. 1200/160 = 7.5 A B. 160/7.5 = 21 ohms

7. A 4-ohm resistor is connected in parallel with a 6-ohm resistor. This combination produces an equivalent resistance of A. 2.4 ohms. B. 5 ohms. C. 10 ohms. D. 5.5 ohms. E. 4 ohms.

A. 2.4 ohms

29. An electric heater is rated at 300 W when used in a 110-V circuit. The safety fuse in the circuit can handle 15 A of current. How many heaters can be safely operated in the circuit? A. 5 B. 3 C. more than 5 D. 2 E. 4

A. 5

1. Consider the three parts of the circuit: the top branch with two bulbs; the middle branch with one bulb; the battery. A. Rank the current through each, from greatest to least. B. Rank the voltage across each from greatest to least.

A. battery, one bulb, two bulbs B. two bulbs, one bulb, battery

25. A capacitor is used to store A. both charge and energy. B. charge. C. energy. D. neither charge nor energy.

A. both charge and energy

10. As more lamps are put into a series circuit, the overall current in the power source A. decreases. B. stays the same. C. increases.

A. decreases

27. Two lamps, one with a thick filament and one with a thin filament of the same material, are connected in series to a battery. The voltage is A. greater across the lamp with the thin filament. B. greater across the lamp with the thick filament. C. the same for both lamps.

A. greater across the lamp with the thin filament

17. Heat a copper wire and its electric resistance A. increases. B. decreases. C. remains unchanged.

A. increases

14. A 100-Watt lamp glows brighter than a 25-Watt lamp. The electrical resistance of the 100-Watt lamp must be A. less. B. greater. C. the same.

A. less

33. Three resistors, 1-ohm, 2-ohm, and 3- ohm are connected in parallel. If they were connected in series instead their equivalent resistance would be A. 13 times as great. B. 11 times as great. C. 7 times as great. D. 9 times as great. E. None of the above choices are correct.

B. 11 times as great

11. Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to a battery. The voltage is A. greatest across the lamp with the thick filament. B. the same in both lamps. C. greatest across the lamp with the thin filament.

B. the same in both lamps

12. Two lamps, one with a thick filament and one with a thin filament, are connected in series. The current is A. greater in the lamp with the thin filament. B. greater in the lamp with the thick filament. C. the same in each lamp.

C. the same in each lamp

3. Given that the power consumed by a device is 1400 W operating on a 140-V line, calculate the amount of current it draws

Power = I x V = 1400/140 = 10 A