Chapter 13 - Electric Circuits

41. An electric iron uses 9.0 A of current and has a power rating of 1100 W. The resistance of the iron is A. 0.0082 . B. 0.074 . C. 14 . D. 120 .

C. 14 .

A household circuit rated at 120 Volts is protected by a fuse rated at 15 amps. What is the maximum number of 100 watt light bulbs which can be lit simultaneously in parallel in this circuit without blowing the fuse? A. 4 B. 8 C. 18 D. 20 E. 24

C. 18

7. What is the best way to ensure that a 40 watt bulb and a 60 watt bulb have the same voltage applied to them? A. Connect the bulbs in series with the power supply ( ) like this: B. Connect the bulbs in parallel with the power supply like this: C. Separately connect the bulbs to two power supplies rated at the same voltage: D. Can't be done: different wattage bulbs must always have different voltages.

B.

28. The potential difference across the terminals of a storage battery not connected in any circuit is observed to be 12 V. When it is connected to an external resistance the potential difference across the terminals is observed to be 11 V while the current in the external resistance is 2 A. What is the internal resistance of the battery? A. zero B. 0.50 ohms C. 1.0 ohm D. 2.0 ohms E. 5.5 ohms

B. 0.50 ohms

20. A 75 watt bulb and a 150 watt bulb are connected in parallel and the combination is connected to a 120 V line. The bulb that will glow more brightly is the A. 75 watt bulb. B. 150 watt bulb. C. both will glow with the same brightness.

B. 150 watt bulb.

33. You have exactly 4 resistors: one 3 , one 4 , one 5 , and one 6 . How can you combine these to make a 2 resistor? (The symbol stands for "ohm".) A. Connect the 3 resistor in series with the 5 resistor. B. Connect the 3 resistor in parallel with the 6 resistor. C. Connect the 3 resistor in parallel with the 4 resistor. D. Connect all four resistors in parallel with each other. E. You can't make a 2 resistor from the ones listed.

B. Connect the 3 resistor in parallel with the 6 resistor.

29. A person discovers that the 5 ampere fuse in his car's brake light circuit is blown. Not having a spare 5 ampere fuse available, he replaces it with a new 10 ampere fuse. What is likely to happen as he uses the brakes? A. The brake lights shine more dimly than before. B. The circuit overheats and the brake lights do not work. C. The fuse blows immediately. D. Nothing bad happens, everything works well for a long time.

B. The circuit overheats and the brake lights do not work.

42. A copper wire from a large spool is cut into two lengths to make extension cords, one 50 feet long and the other 75 feet long. Which of the following is true? A. The longer cord will be able to carry more current. B. The longer cord will have more resistance. C. The shorter cord will dissipate more power. D. The shorter cord will have a smaller voltage.

B. The longer cord will have more resistance.

6. Two light bulbs are installed in two sockets connected in parallel and power is then applied to the combination so that both bulbs light. If one of the bulbs is then removed from its socket, the other one will A. get brighter. B. remain equally bright. C. get dimmer. D. go out.

B. remain equally bright.

9. A 40 W bulb and a 60 W bulb are connected in parallel, and powered by 120 V from household wiring (see sketch). If the 40 W bulb is then removed from its socket, the 60 W bulb will A. get brighter. B. remain equally bright. C. get dimmer. D. go out.

B. remain equally bright.

19. A 12 ohm resistor and a 24 ohm resistor are connected in series with a 6.0 V battery. The correct statement is A. the voltage difference between the ends of each resistor is the same. B. the current in each resistor is the same. C. the power dissipated in each resistor is the same. D. the smaller resistor carries the larger current.

B. the current in each resistor is the same.

36. If the resistance in a circuit using an ideal (no internal resistance) battery is increased, then A. the current coming out of the battery does not change. B. the voltage difference maintained by the battery does not change. C. the power output of the battery does not change. D. All of the choices are correct.

B. the voltage difference maintained by the battery does not change.

27. A student finds two ancient meters with numbered scales but no unit markings. He thinks that one is an ammeter and one is a voltmeter, but doesn't know which is which. He measures the resistance of each, finding that meter A has a resistance of 5000 ohms and meter B has a resistance of 0.10 ohm. He can conclude that A. A is the voltmeter but B cannot be a useful meter. B. B is the voltmeter but A cannot be a useful meter. C. A is the voltmeter and B is the ammeter. D. B is the voltmeter and A is the ammeter. E. Neither can be a useful meter.

C. A is the voltmeter and B is the ammeter.

15. A 1.5 V flashlight battery, a 10 ohm resistor, and a flashlight lamp are available. How should the lamp be connected in a circuit so that it would glow the brightest? A. Connect it in series with the resistor and battery so that the bulb is next to the positive terminal of the battery. B. Connect it in parallel with the battery and the resistor. C. Connect it directly to the battery don't use the resistor. D. Connect it in series with the resistor and battery so that the bulb is next to the negative terminal of the battery.

C. Connect it directly to the battery don't use the resistor.

14. An ohm is equal to which of these? A. a volt B. a coulomb per second C. a volt per ampere D. an ampere per second

C. a volt per ampere

31. Which of these is an electronic instrument that can plot voltage as it varies with time? A. an ammeter B. a galvanometer C. an oscilloscope D. an electroscope

C. an oscilloscope

11. Bulbs A, B, C, and D are identical and connected to a battery as shown. The bulb with the least current passing through it is A. bulb A. B. bulb C. C. both bulb A and B. D. both bulb C and D.

C. both bulb A and B.

5. The resistance of a 25 watt bulb is ______that of a 100 watt bulb, if both run on the same voltage. A. one half B. one fourth C. four times D. double

C. four times

37. Toasters have wires in them that heat up to warm the items placed inside. For the toaster to work properly, these wires must A. be connected to a very large voltage. B. be connected to a tiny voltage. C. have more resistance than the power cord. D. have less resistance than the power cord.

C. have more resistance than the power cord.

3. The resistance of a circuit element is a measure of A. the total energy of the charges in the circuit element. B. the amount of work that an electron can perform. C. the ratio of the voltage difference between element ends to the current in the element. D. the size of the circuit.

C. the ratio of the voltage difference between element ends to the current in the element.

18. A 12 ohm resistor and a 24 ohm resistor are connected in parallel across a 6.0 V battery. The correct statement from the following is A. the current is the same in each resistor. B. the power dissipated is the same in each resistor. C. the voltage difference between the ends of each resistor is the same. D. the larger current is in the larger resistor.

C. the voltage difference between the ends of each resistor is the same.

26. An unmarked resistor is being used in a circuit. To determine its resistance by making voltage and current measurements, one should connect A. the voltmeter and ammeter in parallel with the resistor. B. the voltmeter and ammeter in series with the resistor. C. the voltmeter in parallel with the resistor, and the ammeter in series with the resistor. D. the voltmeter in series with the resistor, and the ammeter in parallel with the resistor.

C. the voltmeter in parallel with the resistor, and the ammeter in series with the resistor.

48. A student finds three resistors in the lab: a two ohm, a five ohm, and a 10 ohm resistor. The smallest value of resistance that the student can make using any one or any combination of the three resistors is ____________ ohms.

1.25

10. What is the best way to ensure that a 40 watt bulb and a 60 watt bulb have the same current within them? A. Connect the bulbs in series with the power supply, like this: B. Connect the bulbs in parallel with the power supply, like this: C. Separately connect the bulbs to two batteries having the same voltage. D. Can't be done: different wattage bulbs must always have different currents.

A.

17. A 6 ohm resistor and a 12 ohm resistor are connected in series in a circuit with a 6.0 volt battery. Assuming negligible internal resistance in the battery, the current in the 12 ohm resistor will be A. 0.33 A. B. 0.5 A. C. 1.0 A. D. 12 A. E. 36 A.

A. 0.33 A.

4. A certain kind of light bulb carries 0.5 amperes of current when connected to a 120 Volt AC circuit. What is its power rating? A. 60 W B. 75 W C. 100 W D. 240 W

A. 60 W

23. Three bulbs have power ratings for use on a 120 volt line: 60 watt, 100 watt and 150 watt. The one with the largest value of resistance has power rating A. 60 W. B. 100 W. C. 150 W. D. all have the same resistance.

A. 60 W.

30. The alternating current in wide use in homes in North America is 60 cycles per second, or 60 Hz. How many times per minute does this current reverse its direction of travel? A. 7200 times B. 3600 times C. 120 times D. 60 times E. None of these.

A. 7200 times

24. A 100 watt bulb is rated for use in a 120 volt line. During a brownout the actual voltage drops to 105 V. The actual power dissipated in the bulb under these conditions is A. 76.6 W. B. 87.5 W. C. 100 W. D. 114 W. E. 131 W.

A. 76.6 W.

8. A 40 W bulb and a 60 W bulb are connected in series with a 120 V power source. Which of the following is true for this arrangement? A. The 40 W bulb is brighter than the 60 W bulb. B. The 60 W bulb is brighter than the 40 W bulb. C. The 60 W bulb is brighter than it would be if the 40 W bulb were replaced by a wire. D. The 40 W bulb is brighter than it would be if the 60 W bulb were replaced by a wire.

A. The 40 W bulb is brighter than the 60 W bulb.

22. The unit for electromotive force (emf) is A. V. B. A. C. ohm. D. N/C. E. N.

A. V.

35. A power rating printed on a light bulb assumes a voltage of 120 V is applied to the bulb. If two 100 W bulbs are connected in series to a 120 V source, A. each bulb radiates less than 100 W. B. each bulb radiates 100 W. C. each bulb radiates more than 100 W. D. no current will pass through the bulbs.

A. each bulb radiates less than 100 W.

12. A flashlight bulb typically has a small metallic button at one end, and this button is surrounded by ceramic material. The chief purpose of the ceramic material is to A. insulate the metal button from the other contact point. B. provide a conducting path to the filament. C. provide extra mass at the bottom of the bulb. D. shut the filament off if the current gets too high.

A. insulate the metal button from the other contact point.

2. The current (measured in Amperes) in a circuit is A. the amount of charge (measured in Coulombs) that passes a point (in the circuit) in 1 second. B. the amount of the total energy carried by 1 Coulomb of charge. C. the total number of electrons in the circuit. D. never lethal if the current is due to positive charges.

A. the amount of charge (measured in Coulombs) that passes a point (in the circuit) in 1 second.

40. Three different resistance light bulbs are connected to a 120-V outlet. The most power will be consumed by the circuit when A. the bulbs are in parallel. B. the bulbs are in series. C. the most resistive bulb is in parallel with a series of the other two. D. the lest resistive bulb is in parallel with a series of the other two. E. the arrangement is unimportant because the voltage is the same in all cases.

A. the bulbs are in parallel.

45. In the water flow analogy with an electric circuit the flow meter in the fluid circuit is analogous to the ________________ in the electric circuit.

Ammeter

16. One ampere is equivalent to: A. 1 V/m. B. 1 N/C. C. 1 J/s. D. 1 C/s. E. 1 ohm/volt.

D. 1 C/s.

25. A heater is rated to dissipate 1800 W when connected to a 120 V source. The current drawn by the device is A. 1800 A. B. 120 A. C. 30 A. D. 15 A. E. 0.067 A.

D. 15 A.

21. The voltage drop across a resistor is 1.0 V for a current of 3.0 A in the resistor. What is the current that will produce a voltage drop of 9.0 V across the resistor? A. 0.33 A B. 1 A C. 9 A D. 27 A

D. 27 A

38. Resistors of 10 ohms, 20 ohms, and 30 ohms are connected in series with a battery. The 10 ohm resistor is closest to the positive terminal and the 30 ohm resistor is closest to the negative terminal. What happens as the current flows through this circuit? A. A little current is consumed in the 10 ohm resistor, more in the 20 ohm, and the most in the 30 ohm. B. The most current is consumed in the 10 ohm resistor, less in the 20 ohm resistor, and the least in the 30 ohm. C. The resistors each consume the same amount of current. D. None of the resistors consume current.

D. None of the resistors consume current.

32. When you pay your electric bill, what are you paying for, exactly? A. The voltage you used the previous month. B. The electrical charge you used the previous month. C. The electrical power you used the previous month. D. The electrical energy you used the previous month. E. None of these.

D. The electrical energy you used the previous month.

39. The current through a circuit consisting of a single battery and single resistor is measured to be 0.25 amperes. Another identical battery and another identical resistor are added to the circuit. The current passing through the circuit A. 0.125 A. B. 0.25 A. C. 0.50 A. D. depends on how the battery and resistor are added to the circuit.

D. depends on how the battery and resistor are added to the circuit.

13. In many ways, and electric circuit is like the plumbing system in your home. The switch in an electric circuit corresponds to the ________ in a plumbing system. A. drain. B. trap. C. bathtub. D. faucet or valve.

D. faucet or valve.

34. Three identical resistors can be connected in any combination. It's not necessary to include all three in any given combination. The number of distinct values of resistance that can be made is A. two or fewer. B. three. C. four. D. five. E. six or more.

E. six or more.

49. In a series circuit, the most power is dissipated where the resistance is __________.

Greatest

43. A resistor R is connected across a battery of negligible internal resistance. If the resistance of R is doubled, the current in R will be __________.

Halved

51. A resistor R is connected across a battery of negligible internal resistance. If the resistance of R is cut in half, the power dissipated in R will ______________ (indicate change, if any).

Increase 2x

47. A dry cell is no longer useful when its ___________________ (two words) becomes large.

Internal Resistance

46. A one ohm, a two ohm, and a three ohm resistor are connected in parallel in an electric circuit: The resistor dissipating the most power will be the ____________ ohm resistor.

One

50. As the temperature of a wire increases, its ___________ also increases.

Resistance

44. In the water flow analogy with an electric circuit the pressure in the fluid circuit is analogous to ______________ in the electric circuit.

Voltage