3. Physics Practice Questions Chapter 23

B

10) In an ac circuit, the electric field A) increases via the inverse square law. B) changes magnitude and direction with time. C) is everywhere the same. D) is non-existent. E) none of these.

C

11) The current through a 10-ohm resistor connected to a 120-V power supply is A) 1 A. B) 10 A. C) 12 A. D) 120 A. E) none of these

E

12) A 10-ohm resistor has a 5-A current in it. What is the voltage across the resistor? A) 5 V B) 10 V C) 15 V D) 20 V E) more than 20 V

B

13) 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) 2 ohms B) 5 ohms C) 10 ohms D) 20 ohms E) more than 20 ohms

D

14) The source of electrons in an ordinary electrical circuit is A) a dry cell, wet cell or battery. B) the back emf of motors. C) the power station generator. D) the electrical conductor itself. E) none of these.

C

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

A

16) A woman experiences an electrical shock. The electrons making the shock come from the A) woman's body. B) ground. C) power plant. D) hairdryer. E) electric field in the air.

A

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

D

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

B

2) An ampere is a unit of electrical A) pressure. B) current. C) resistance. D) all of these. E) none of these.

E

20) The electric power of a lamp that carries 2 A at 120 V is A) 1/6 watts. B) 2 watts. C) 60 watts. D) 20 watts. E) 240 watts.

B

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

A

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

C

23) On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in A) parallel. B) perpendicular. C) series. D) haste.

A

24) Modern automobile headlights are connected in A) parallel. B) perpendicular. C) series. D) none of these.

B

25) 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) different electrons; the ones that flow in the circuit to your lamp. B) the same electrons. C) the positive charges that flow in the filament.

A

26) 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

27) In an electric circuit, the safety fuse is connected to the circuit in A) series. B) parallel.

D

28) When a pair of 1-ohm resistors are connected in series, their combined resistance is A) 1 ohm, and when connected in parallel, 2 ohms. B) 2 ohms, and when in parallel, 1 ohm. C) 1/2 ohm, and when in parallel, 2 ohms. D) 2 ohms, and when in parallel, 1/2 ohm. E) none of these.

B

29) A circuit breaker serves the same purpose as A) a switch. B) a fuse. C) a capacitor. D) a battery. E) none of these.

C

30) A capacitor is useful in A) boosting the energy output of a circuit. B) increasing the current in a resistor. C) smoothing pulsed current. D) switching dc to ac in a circuit. E) increasing or decreasing voltage.

E

31) An electrical diode is useful for A) storing electrical energy. B) boosting voltage. C) limiting current. D) voltage modification. E) changing ac to dc.

C

Which of the following is not true: Electric power A. is the rate at which electrical energy is transmitted B. is the rate at which energy is stored in electric fields or magnetic fields C. is measured in watt/s D. according to Joule's Law, is the product of applied voltage and the electric resistance.

D

Which of the following is not true: Resistance A. is a property of a material that determines how fast electric charge flows. B. is measured in ohm C. increases with the length D. increases with the thickness or sectional area

D

45) If you plug an electric toaster rated at 110 V into a 220-V outlet, the current in the toaster will be about A) half what it should be. B) the same as if it were plugged into 110 V. C) more than twice what it should be. D) twice what it should be.

B

46) A 60-watt light bulb is connected to a 120-volt plug. What is the current in the light bulb? A) 0.25 A B) 0.5 A C) 2 A D) 4 A E) more than 4 A

D

47) What is the power rating of a light bulb if 0.8 A flow through it when it is connected to a 120-volt outlet? A) 12 W B) 15 W C) 60 W D) 96 W E) 120 W

B

48) The headlights, radio, and defroster fan in an automobile are connected in A) series. B) parallel.

A

49) 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) 4 ohms. C) 5 ohms. D) 5.5 ohms. E) 10 ohms.

A

5) Which statement is correct? A) Charge flows in a circuit. B) Voltage flows through a circuit. C) Resistance is established across a circuit. D) Current causes voltage.

A

51) Which is more dangerous, touching a faulty 110-volt light fixture, or a Van de Graaff generator charged to 100,000 volts? A) touching the light fixture B) touching the generator C) Touching both are about equally dangerous.

A

52) A 60-W light bulb and a 100-W light bulb are each rated at 120 V. Which light bulb has a larger resistance? A) the 60-W bulb B) the 100-W bulb C) Both have the same resistance.

B

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

B

55) 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.

A

56) Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry A) more current. B) less current. C) the same current.

D

57) 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) 2 B) 3 C) 4 D) 5 E) more than 5

C

58) 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) $0.22. B) $0.55. C) $2.20. D) $5.50. E) none of these.

C

59) The current through two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is A) 22 ohms. B) 44 ohms. C) 220 ohms. D) 440 ohms. E) none of these.

C

6) Electrons move in an electrical circuit A) by being bumped by other electrons. B) by colliding with molecules. C) by interacting with an established electric field. D) because the wires are so thin. E) none of these.

D

60) 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) 40 W. B) 160 W. C) 320 W. D) 12,800 W. E) none of these.

E

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

D

62) Compared to the amount of electric current in the filament of a lamp, the amount of current in the connecting wire is A) definitely less. B) often less. C) actually more. D) the same. E) incredibly, all of these.

B

63) Connect a pair of lamps in series and you draw current from the connected battery. Connect the same lamps in parallel and you draw A) the same current. B) more current. C) less current. D) ...sometimes more, sometimes less.

C

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

C

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

C

9) A wire carrying a current is normally charged A) negatively. B) positively. C) not at all.

A

A coulomb of charge that passes through a 6-volt battery is given A) 6 joules. B) 6 amperes. C) 6 ohms. D) 6 watts. E) 6 newtons

C

Which of the following is true: A. Electricity is carried by charged particles called ions. B. Sweat is a good conductor of electricity because it is an ionic solution. C. Sugar water is a good conductor of electricity because it is an ionic solution

A

Which statement is correct? A) Charge flows in a closed circuit. B) Voltage flows through an open or a closed circuit. C) Resistance flows though an open circuit. D) Current is the primary cause of voltage.

C

When an electric current passes through a wire it warms up because of A. fire burning inside it B. chemical energy is converted to heat in the wire C. collisions between charge carriers and atoms D. potential energy is converted to heat in the wire

B

Which of the following is not true: Electric current is A. due to electrons, which are the mobile charge carriers, moving in conductors such as wires. B. measured in Ampere/sec C. a flow of charge from high to low potential energy D. flows in the direction of moving positive charges

C

1) Electrons are made to flow in a wire when there is A) an imbalance of charges in the wire. B) more potential energy at one end of the wire than the other. C) a potential difference across its ends.

B

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

C

34) A capacitor is used to store A) charge. B) energy. C) both. D) neither.

C

50) The power dissipated in a 4-ohm resistor carrying 3 A is A) 7 W. B) 18 W. C) 36 W. D) 48 W. E) not enough information to say.

B

54) Compared to the filament thickness of a 60-W light bulb, the filament of a 100-W light bulb will be A) thinner. B) thicker. C) the same.

B

A wire that carries an electric current A) is electrically charged. B) may be electrically charged. C) is never electrically charged.

C

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

C

33) In the circuit of Figure 23-A, energy is given to the moving charges by A) the bulb. B) the wires. C) a generator which is not shown. D) none of these.

A

35) The number of electrons delivered daily to an average American home by an average power utility in the mid 1980s was A) zero. B) 110. C) 220. D) billions of billions. E) none of these.

C

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

C

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

A

38) 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 larger in the lamp with the A) thick filament. B) thin filament. C) current is the same in both.

B

39) 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 greater across the lamp with the A) thick filament. B) thin filament. C) voltage is the same for both.

A

4) A coulomb of charge that passes through a 6-volt battery is given A) 6 joules. B) 6 amperes. C) 6 ohms. D) 6 watts. E) 6 newtons.

B

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

A

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

D

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

E

43) When we say an appliance "uses up electricity," we really are saying that A) current disappears. B) electric charges are dissipated. C) the main power supply voltage is lowered. D) electrons are taken out of the circuit and put somewhere else. E) electron kinetic energy is changed into heat.

B

44) Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have A) more resistance. B) less resistance. C) the same resistance.

Fuses protect electrical devices by opening a circuit if the current in the circuit is too high. Would a fuse work successfully if it were connected in parallel with the device that it is supposed to protect?

A fuse will Not work in parallel because there is an alternative path for the current.

B

Ohm's Law states: A. The potential difference (voltage) across a conductor is constant always. B. As the voltage across a conductor increases the current through it increases C. As the voltage across a conductor increases the current through it decreases D. The resistance across a conductor increases as the current through it increases

Suppose a 9 V battery is connected across a light bulb. In what form is the electrical energy supplied by the battery dissipated by the light bulb?

Some of the electrical energy is dissipated by heat, and the remainder is converted into light energy.

D

The primary source of electrons in an ordinary electrical circuit is A) a dry cell, wet cell or battery. B) the back emf of motors. C) the power station generator. D) the electrical circuit itself. E) none of these

Why do wires usually warm up when an electric current is in them?

They usually warm up because of collisions between charge carriers and atoms.

D

What is the drift velocity of an electron in a wire that has alternating current in it? A. 60 Hz B. It depends on the current. C. It depends on the voltage. D. zero