Chapter 13: Electric Circuits

Transcription

1 Chapter 13: Electric Circuits 1. 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 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. 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. 4. A certain kind of light bulb carries 1.5 amperes of current when connected to a 120 Volt AC circuit. What is its power rating? A. 240 W B. 180 W C. 80 W D. 100 W 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

2 6. Two light bulbs are installed in two sockets, the sockets are connected in series, 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. 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. 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. 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.

3 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. 11. Bulbs A, B, C, and D are connected to a battery ( ) as shown. The bulb with the greatest voltage is A B A. bulb A. B. bulb C. D C. both bulb A and bulb C. D. both bulb C and bulb D. C 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. 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.

4 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 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. 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. 17. A 12 ohm resistor and a 24 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. 6.0 A. B. 2.0 A. C A. D A. E A. Answer: E 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.

5 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. 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. 21. The voltage drop across a resistor is 3.0 V for a current of 1 A in the resistor. What is the current that will produce a voltage drop of 9.0 V across the resistor? A. 1 A B. 3 A C. 0.33A D. 27 A 22. The unit for electromotive force (emf) is A. V. B. A. C. ohm. D. N/C. E. N. 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.

6 24. A 100 watt bulb is rated for use in a 120 volt line. During a brownout the actual voltage drops to 100 V. The actual power dissipated in the bulb under these conditions is A. 120 W. B. 100 W. C W. D W. E W. 25. A heater is rated to dissipate 1800 W when connected to a 120 V source. The current drawn by the device is A A. B. 120 A. C. 30 A. D. 15 A. E A. 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. 27. A student finds two ancient meters with numbered scales but no unit markings. He knows 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 and B is the ammeter. B. B is the voltmeter and A is the ammeter. C. no conclusion can be made from only these measurements. 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 ohms. C. 1.0 ohm. D. 2.0 ohms. E. 5.5 ohms.

7 29. A certain simpleton 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 7 ampere fuse. Next time he steps on the brake, various wires in the brake light circuit self-destruct due to overheating. Compared to the heat allowed by the 5A fuse, how much more is allowed by the 7A fuse? A. 20 % more B. 24 % more C. 48 % more D. 96 % more E. 192 % more 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 times B times C. 120 times D. 60 times E. none of these 31. Which of these is an electronic instrument that can plot voltage as it varies with time? A. an oscilloscope B. a stethoscope C. a kaleidoscope D. a fluoroscope E. none of these 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. 33. You have exactly 4 resistors: one 3 Ω, one 4 Ω, one 5 Ω, and one 6 Ω. How can you combine these to make a 2 Ω resistor? (The symbol Ω stands for "ohm".) A. Connect the 3 Ω resistor in series with the 5 Ω resistor. B. Connect the 3 Ω resistor in parallel with the 6 Ω resistor. C. Connect the 3 Ω resistor in parallel with the 4 Ω resistor. D. Connect all four resistors in parallel with each other. E. You can't make a 2 Ω resistor from the ones listed.

8 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. Answer: E 35. 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. Answer: halved 36. 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). Answer: increase (by a factor of two). 37. In the water flow analogy with an electric circuit the pressure in the fluid circuit is analogous to in the electric circuit. Answer: voltage 38. In the water flow analogy with an electric circuit the flow meter in the fluid circuit is analogous to the in the electric circuit. Answer: ammeter 39. A one ohm, a two ohm, and a three ohm resistor are connected in series in an electric circuit: The resistor dissipating the most power will be the ohm resistor. Answer: three 40. A dry cell is no longer useful when its (two words) becomes large. Answer: internal resistance 41. 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. Answer: 1.25