Preview Extract
Chapter 8 Static and Current Electricity
8.1 Electric Charge
1) The nucleus of an atom is charged
A) positively.
B) negatively.
C) both
D) none of the above
Answer: A
2) The electric charge on all electrons
A) vary from atom to atom.
B) vary from ion to ion.
C) are identical.
Answer: C
3) Compared to the mass of a proton, the mass of the electron is
A) very much less.
B) identical.
C) greater.
Answer: A
4) When you remove electrons from a metal cup, the cup becomes
A) negatively charged.
B) positively charged.
C) ionized.
Answer: B
5) Which force binds atoms together to form molecules?
A) gravitational
B) nuclear
C) electric
D) centripetal
E) none of the above
Answer: C
6) The fundamental force underlying all chemical reactions is
A) gravitational.
B) nuclear.
C) centripetal.
D) electrical.
E) none of the above
Answer: D
7) A pair of positively-charged plastic straws tend to
A) attract each other.
B) repel each other.
C) neutralize each other.
Answer: B
8) An electron and a proton
A) attract each other.
B) repel each other.
C) attract or repel depending on distance.
Answer: A
9) The number of protons in the nucleus of an electrically neutral atom is equal to the number of
A) electrons that surround the nucleus.
B) neutrons in the nucleus.
C) both
D) neither
Answer: A
10) A positive ion has a deficiency of
A) electrons.
B) neutrons.
C) negative ions.
Answer: A
11) A rubber rod rubbed with fur becomes
A) positively charged.
B) negatively charged.
C) both
D) neither.
Answer: B
12) If you strip electrons from an atom, the atom becomes a
A) positive ion.
B) negative ion.
C) different element.
Answer: A
13) To say that electric charge is conserved is to say that electric charge
A) may occur in an infinite variety of quantities.
B) is a whole-number multiple of the charge of one electron.
C) will interact with neighboring electric charges.
D) can neither be created nor destroyed.
Answer: D
14) To say that electric charge is conserved means that no case has ever been found where
A) the net charge on an object has changed.
B) the net amount of charge on an object has increased.
C) net charge has been created or destroyed.
D) none of the above
Answer: C
15) As you comb your hair, electrons are rubbed onto the comb, which becomes
A) negatively charged.
B) positively charged.
C) ionized.
Answer: A
16) When you scuff electrons from a carpet onto your feet, you become
A) negatively charged.
B) positively charged.
C) polarized.
D) ionized.
E) neutralized.
Answer: A
17) A difference between an insulator and a conductor is that a conductor has more
A) electrons than protons.
B) protons than electrons.
C) energy than an insulator.
D) faster moving molecules.
E) none of the above
Answer: E
18) Charge carriers in a metal are electrons rather than protons because electrons are
A) negative.
B) smaller.
C) loosely bound.
D) all of the above
E) none of the above
Answer: C
19) A negatively charged rod is brought near a metal can that rests on a wood table. You touch
the opposite side of the can momentarily with your finger. The can then becomes
A) positively charged.
B) negatively charged.
C) uncharged.
Answer: A
8.2 Coulomb's Law
1) The unit of electric charge, the coulomb, is the charge on
A) one electron.
B) one proton.
C) a specific large number of electrons.
Answer: C
2) One main difference between gravitational and electric forces is that electric forces
A) attract.
B) repel or attract.
C) obey the inverse-square law.
D) act over shorter distances.
E) are weaker.
Answer: B
3) A difference between electric and gravitational forces is that electric forces include
A) separation distance.
B) repulsive interactions.
C) the inverse-square law.
D) infinite range.
E) none of the above
Answer: B
4) The electric force between charges is strongest when the charges are
A) close together.
B) far apart.
C) either
Answer: A
5) The electric force between charges depends on the
A) magnitude of electric charges.
B) separation distance between electric charges.
C) both
D) none of the above
Answer: C
6) When the distance between two charges is halved, the electric force between the charges
A) quadruples.
B) doubles.
C) is half.
D) is reduced by one-quarter.
E) none of the above
Answer: A
7) Two charges separated by 1 m exert a 1.0-N force on each other. If the charges are pushed to
0.25-m separation, the force on each charge will be
A) 1 N.
B) 2 N.
C) 4 N.
D) 8 N.
E) 16 N.
Answer: E
8) Two charges separated by 1 m exert a 1.0-N force on each other. If the charges are pulled to a
3-m separation distance, the force on each charge will be
A) 0.33 N.
B) 0.11 N.
C) 0 N.
D) 3 N.
E) 9 N.
Answer: B
9) Two charges separated by 1 m exert a 1-N force on each other. If the magnitude of each
charge is doubled, the force on each charge will be
A) 1 N.
B) 2 N.
C) 4 N.
D) 8 N.
E) none of the above
Answer: C
10) Two charged particles near each other are released. As they move, the force on each particle
increases. Therefore, the particles have
A) the same sign.
B) the opposite sign.
C) not enough information
Answer: B
11) Two charged particles near each other are released. As the particles move, the velocity of
each increases. Therefore, the particles have
A) the same sign.
B) the opposite sign.
C) not enough information
Answer: C
12) A positive and a negative charge near each other are released. As they move, the force on
each particle
A) increases.
B) decreases.
C) stays the same.
Answer: A
13) Two charged particles repel each other will a force F. If the charge on one particle is doubled
and the distance between them is doubled, the force will be
A) F.
B) 2 F.
C) F/2.
D) F/4.
E) none of the above
Answer: C
14) To say that an object is electrically polarized is to say
A) it is electrically charged.
B) its charges have been rearranged.
C) its internal electric field is zero.
D) it is only partially conducting.
E) it is to some degree magnetic.
Answer: B
15) An electrically polarized object normally has
A) a net charge of zero.
B) displaced charges.
C) both
D) neither
Answer: C
16) A balloon will stick to a wooden wall if the balloon is charged
A) negatively.
B) positively.
C) either
D) neither
Answer: C
17) A negatively-charged balloon touching a wooden wall
A) pulls positive charge on the wall surface toward it.
B) pushes negative charge in the wall away from it.
C) polarizes molecules in the wall.
D) all of the above
E) none of the above
Answer: D
18) A water molecule is electrically
A) polarized.
B) conducting.
C) insulating.
D) charged.
Answer: A
19) Food cooked in a microwave oven depends on electrical
A) conduction.
B) charge polarization.
C) resistance changes.
D) field strength.
E) all of the above
Answer: B
20) What are the similarities and differences between Coulomb's law and Newton's law of
gravitation?
Answer: Similarities: Both laws are inverse-square laws and are directly dependent on the
quantities involved: electric charge for electric force, and mass for gravitational force.
Differences: The Coulomb force between a pair of electrons is many billions of times greater
than the gravitational force between them. Also, whereas the gravitational force is only
attractive, the Coulomb force can be attractive or repulsive.
8.3 Electric Field
1) The direction of an electric field is defined as the direction of force on a
A) charged particle.
B) a positively-charged particle.
C) a negatively-charged particle.
Answer: B
2) Electric field lines about a point charge extend
A) outward when the charge is negative.
B) outward when the charge is positive.
C) in circles.
Answer: B
3) Every proton in the universe is surrounded by its own
A) electric field.
B) gravitational field.
C) both
D) none of the above
Answer: C
4) The electric field around an isolated electron has a certain strength 1 cm from the electron.
The electric field strength 2 cm from the electron is
A) half as much.
B) the same.
C) twice as much.
D) four times as much.
E) none of the above
Answer: E
5) A proton and an electron are placed in an electric field. Which undergoes the greater
acceleration?
A) the electron
B) the proton
C) both equally
D) neither
Answer: A
6) The electric force on a 2-C charge is 60 N. How great is the electric field at the charge
location?
A) 20 N/C
B) 30 N/C
C) 60 N/C
D) 120 N/C
E) 240 N/C
Answer: B
7) Measurements show there is an electric field surrounding the Earth. Its magnitude averages
100 N/C at the Earth's surface and it points inward toward the Earth's center. From this
information, state whether the Earth is negatively or positively charged. Defend your answer.
Answer: The Earth is negatively charged. If it were positively charged, the electric field would
point outward. The electric field direction is that in which a positive test charge would be moved
by the electric field.
8.4 Electric Potential
1) Electric potential is measured in units of
A) volts.
B) joules.
C) amperes.
D) watts.
E) any or all of these
Answer: A
2) Electric potential energy is measured in units of
A) volts.
B) joules.
C) amperes.
D) watts.
E) any or all of these
Answer: B
3) If you do 10 J of work to push 1 coulomb of charge into an electric field, its voltage with
respect to its starting position is
A) less than 10 V.
B) 10 V.
C) more than 10 V.
Answer: B
4) If you do 10 J of work to push a charge into an electric field and then release the charge, as it
flies past its starting position, its kinetic energy is
A) less than 10 J.
B) 10 J.
C) more than 10 J.
Answer: B
5) When a battery does 24 J of work on 10 C of charge, the voltage it supplies is
A) 2.4 V.
B) 4.2 V.
C) 24 V.
D) 240 V.
E) none of the above
Answer: A
6) A charged balloon illustrates that something can have a great amount of
A) potential energy and a low voltage.
B) voltage and a small potential energy.
C) both voltage and potential energy.
D) none of the above
Answer: B
7) Normally a balloon charged to several thousand volts has a relatively small amount of
A) charge.
B) energy.
C) both
D) neither
Answer: C
8) Which is more dangerous, touching a faulty 120-V light fixture, or a Van de Graaff generator
charged to 100,000 V?
A) light fixture
B) generator
C) both equally
Answer: A
9) The reason that Lillian's hair stands out when her hand is on a charged Van de Graaff
generator is
A) strands of hair become charged and repel one another.
B) a high voltage is communicated to strands of hair.
C) strands of hair find themselves in an electric field.
D) electrons and protons are deposited on her hair.
Answer: A
10) Lillian touches a 100,000-V Van de Graaff generator with little harm because although the
voltage is high, the relatively small amount of charge means there is a relatively small
A) amount of energy.
B) electric field.
C) polarization.
D) conduction.
Answer: A
11) An electron is pushed into an electric field where it acquires a 1-V electric potential. If two
electrons are pushed the same distance into the same electric field, the electric potential of both
electrons is
A) 0.25 V.
B) 0.5 V.
C) 1 V.
D) 2 V.
E) 4 V.
Answer: C
8.5 Voltage Sources
1) Just as water flows from high to low pressure, electric charge flows from
A) high to low voltage.
B) high charge concentration to low charge concentration.
C) high resistance to low resistance.
D) all of the above
E) none of the above
Answer: A
2) The flow of charge in a circuit depends on
A) adequate resistance.
B) a potential difference.
C) adequate chemical action.
D) all of the above
Answer: B
3) The purpose of a voltage source is to provide an electrical
A) energy sink.
B) field.
C) pressure.
Answer: C
4) A sustained electric current can be achieved with a
A) generator.
B) battery.
C) both
D) none of the above
Answer: C
5) A sustained flow of electric charge requires
A) a potential difference.
B) a resistance.
C) an electric field.
D) electric polarization.
Answer: A
6) A term for electric pressure is
A) current.
B) voltage.
C) electric resistance.
Answer: B
7) Compared to the work input to charge an electrostatic generator, the energy output is
A) less.
B) more.
C) no more.
Answer: C
8) The amount of energy given to each coulomb of charge flowing through a 12-V battery is
A) 12 J.
B) 12 A.
C) 12 V.
D) all of the above
E) none of the above
Answer: A
8.6 Electric Current
1) Electric charge will flow in an electric circuit when
A) electric resistance is low.
B) a potential difference exists.
C) the circuit is grounded.
D) electric devices in the circuit are not defective.
Answer: B
2) Electrons 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 end.
C) a potential difference across its ends.
Answer: C
3) A flow of electrons move in an electric circuit by
A) bumping other electrons.
B) colliding with molecules.
C) interacting with an established electric field.
D) none of the above
Answer: C
4) The electric current in a copper wire is normally composed of
A) electrons.
B) protons.
C) ions.
D) all or any of the above
Answer: A
5) An ampere is a unit of electric
A) pressure.
B) current.
C) resistance.
D) all of the above
E) none of the above
Answer: B
6) The electric charge on a current-carrying wire is normally
A) zero.
B) equal and opposite to the charge within the wire.
C) the voltage divided by the resistance.
Answer: A
7) A coulomb of charge passing through a 6-V battery supplies
A) 6 joules.
B) 6 amperes.
C) 6 ohms.
D) 6 watts.
E) 6 newtons.
Answer: A
8) Which statement is correct?
A) charge flows through a circuit
B) voltage flows through a circuit
C) resistance is established across a circuit
D) current causes voltage
Answer: A
9) Which statement is correct?
A) voltage flows through a circuit
B) voltage flows across a circuit
C) voltage is impressed across a device in a circuit
Answer: C
10) The electric field in the wires of an ac circuit
A) changes via the inverse square law.
B) changes direction with time.
C) remains relatively constant.
D) is nonexistent.
E) none of the above
Answer: B
11) To say a circuit is dc is to say that current in the circuit
A) has a single direction.
B) alternates only slowly.
C) is parallel to the connecting wires.
Answer: A
12) The source of electrons in an ordinary electric circuit is
A) a dry cell, wet cell, or battery.
B) usually a wall socket.
C) a generator at the power station.
D) the electric conductor itself.
E) none of the above
Answer: D
13) The source of electrons lighting an incandescent ac light bulb is
A) the power company.
B) the electric outlet.
C) atoms in the light bulb filament.
D) the wire leading to the lamp.
E) the source voltage.
Answer: C
14) In a common dc circuit, electrons typically move at the speed of
A) a fraction of a centimeter per second.
B) a few meters per second.
C) sound.
D) light.
E) none of the above
Answer: A
15) 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.
Answer: D
16) The origin of the glow from the filament inside the ac incandescent lamp in your bedroom is
A) electrons resupplied by the wall outlet.
B) electrons already in the filament.
C) the positive charges that flow in the filament.
D) resistance in the filament.
Answer: B
17) The number of electrons delivered daily by power utilities to an average American home in a
typical year in this century is
A) zero.
B) 110.
C) 220.
D) billions of billions.
E) none of the above
Answer: A
18) When you purchase a water pipe in a hardware store, water is not included. When you
purchase copper wire, electrons
A) must be supplied by you, just as water in a water pipe.
B) already exist in the wire.
C) may fall out, which is why wires are insulated.
D) none of the above
Answer: B
19) A circuit is powered with a battery. It is best to say that electrons flow
A) from the battery and into the circuit.
B) from the negative terminal to the positive terminal of the battery.
C) after a couple seconds passes.
D) through both the battery and the devices making up the circuit.
E) none of the above
Answer: D
20) When we say an appliance "uses up" electricity, we actually 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) electrical energy changes to thermal energy.
Answer: E
21) Distinguish between ac and dc. When you plug a light bulb into a wall outlet, where is the
source of electrons?
Answer: AC is alternating current, where electrons do not migrate but simply alternate about
relatively fixed positions. In dc, the flow of electrons is in one direction only. Migration does
occur, but the source of electrons, whether in a dc or ac circuit, is the electric conductor itself.
You can buy a water pipe in a hardware store with no water inside, but you can't buy an electron
pipe without its supply of electrons. Wires and all materials have electrons in them.
22) What is an electric current? How does it move in a wire? How fast do the electrons move?
Answer: Electric current is the flow of electric charge in a circuit. In a wire, current is the motion
of electrons through the wire. Electrons move at extremely high speeds about the atomic nucleus
and through empty space. But in a wire or other conductor they have so many collisions each
second that their overall progress through the wire is only a small fraction of a centimeter per
second. If the current is ac, then electrons don't have any net flow-they vibrate to and fro about
relatively fixed positions.
8.7 Electrical Resistance
1) The unit of resistance is named after
A) Isaac Newton.
B) Benjamin Franklin.
C) Georg Simon Ohm.
D) Micheal Faraday.
E) Charles Coulomb.
Answer: C
2) A length of wire has resistance R. The same wire twice as long has resistance
A) R/2.
B) R.
C) 2R.
D) none of the above
Answer: C
3) A length of wire has resistance R. Two of these same-length wires braided together have a
resistance
A) R/2.
B) R.
C) 2R.
D) none of the above
Answer: A
4) Stretch a copper wire so that it is thinner and the resistance between its ends
A) decreases.
B) remains unchanged.
C) increases.
Answer: C
5) Heat a copper wire and its electric resistance
A) decreases.
B) remains unchanged.
C) increases.
Answer: C
6) Electric resistance is normally measured in
A) amperes.
B) volts.
C) newtons.
D) joules.
E) none of the above
Answer: E
7) The electric resistance of a superconductor is
A) zero.
B) infinite.
C) usually lower than that of ordinary resistors.
Answer: A
8) What is the difference between an insulator and a conductor of electricity? Give examples of
each.
Answer: An insulator is any material composed of atoms with tightly bound outer electrons, such
a wood, rubber, glass, and distilled water. A good electric conductor is any material composed of
atoms with "loose" outer electrons that are free to move about in the material. Any metal, most
notably silver and copper, are good examples of conductivity.
9) What is electric resistance? What characteristics of a wire determine its resistance? How does
resistance normally vary with temperature?
Answer: Electric resistance is the opposition a conductor offers to the migration of electrons. It
depends on the wire material and dimensions of the wire. Resistance generally increases with
increasing temperature. In some materials, called superconductors, resistance decreases to zero at
critically low temperature.
8.8 Ohm's Law
1) When the voltage across a steady resistance is doubled, the current
A) is half.
B) remains the same.
C) is doubled.
D) is quadrupled.
Answer: C
2) When a steady voltage is across one-half as much resistance, the current
A) is half.
B) remains the same.
C) is doubled.
D) is quadrupled.
Answer: C
3) Electrical resistance is greater for
A) dry skin.
B) wet skin.
C) both the same
Answer: A
4) 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 the above
Answer: C
5) The current in a 10-ohm resistor is 5 A. What is the voltage across the resistor?
A) 5 V
B) 10 V
C) 15 V
D) 20 V
E) more than 20 V
Answer: E
6) A resistor carries a current of 2 A when connected to a 10-V battery. What is the resistor's
value?
A) 2 ohms
B) 5 ohms
C) 10 ohms
D) 20 ohms
E) more than 20 ohms
Answer: B
7) When a person experiences an electric shock, the origin of the electrons comprising the shock
is
A) the person's own body.
B) the ground.
C) a power plant.
D) likely a faulty lamp.
E) the electric field in the air.
Answer: A
8) A bird can sit harmlessly on a high-voltage wire because
A) the wire is insulated.
B) no potential difference is across the birds feet.
C) current is inside the wire.
D) the net charge on a current-carrying wire is zero.
E) all of these.
Answer: B
9) The purpose of the third prong on a common electric plug for an appliance is to
A) handle three-phase electricity.
B) provide an alternate live wire.
C) connect the appliance to zero ground potential.
D) substitute for a safety fuse.
E) all of these.
Answer: C
10) If you plug an electric toaster rated at 110-V into a 220-V outlet, current in the toaster will be
about
A) half what is 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.
Answer: D
11) 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 the above
Answer: C
12) Which will do more damage, plugging a 120-V hair dryer into a 240-V circuit or plugging a
220-V hair dryer into a 120-V circuit? Explain.
Answer: Damage generally occurs from excess heating caused by too much current in a device.
For an appliance that converts electric energy directly to heat, such as a hair dryer, this occurs
when excess voltage is applied. So don't connect a 120-V device to a 240-V circuit. To be safe,
use the recommended voltage for an appliance.
8.9 Electric Circuits
1) Compared to a single lamp connected to a battery, two identical lamps connected in series to
the same battery will draw
A) more current.
B) less current.
C) the same current.
Answer: B
2) Compared to a single lamp connected to a battery, two lamps connected in parallel to the same
battery will draw
A) more current.
B) less current.
C) the same current.
Answer: A
3) 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) same in each
Answer: C
4) Two lamps, one with a thick filament and one with a thin filament, are connected in parallel.
The current is greater in the lamp with the
A) thick filament.
B) thin filament.
C) same in each
Answer: A
5) Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to
a battery. The voltage is greater across the lamp with the
A) thick filament.
B) thin filament.
C) same for each
Answer: C
6) Two lamps, one with a thick filament and one with a thin filament, are connected in series to a
battery. The voltage is greater across the lamp with the
A) thick filament.
B) thin filament.
C) same for both
Answer: B
7) When two lamps are connected in series to a battery, the electric 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 the above
Answer: A
8) When two lamps are connected in parallel to a battery, the electric 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 the above
Answer: B
9) In an electric circuit, the safety fuse is connected to the circuit in
A) series.
B) parallel.
C) such a way to reduce danger.
Answer: A
10) A pair of 1-ohm resistors connected in series has a combined resistance of
A) 1 ohm.
B) 2 ohms.
C) 1/2 ohm.
D) none of the above
Answer: B
11) A pair of 1-ohm resistors connected in parallel has a combined resistance of
A) 1 ohm.
B) 2 ohms.
C) 1/2 ohm.
D) none of the above
Answer: C
12) As more lamps are put into a series circuit, the overall current in the power source
A) increases.
B) decreases.
C) stays the same.
Answer: B
13) As more lamps are put into a parallel circuit, the overall current in the power source
A) increases.
B) decreases.
C) remains the same.
Answer: A
14) 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.
Answer: B
15) More toll booths on a highway is analogous to a
A) series circuit.
B) parallel circuit.
C) complex series/parallel circuit.
Answer: B
16) The headlights, radio, and defroster fan in an automobile are connected in
A) series.
B) parallel.
C) order of energy efficiency.
Answer: B
17) 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 the above
Answer: D
18) Connect a pair of lamps in series and you draw current from the connecting battery. Connect
the same lamps in parallel and you draw
A) the same current.
B) more current.
C) less current.
Answer: B
8.10 Electric Power
1) When we talk about electric power we're talking
A) joules per second.
B) watts.
C) both
D) neither
Answer: C
2) The electric power of a lamp that carries 2 A at 120 V is
A) 1/6 W.
B) 2 W.
C) 60 W.
D) 20 W.
E) 240 W.
Answer: E
3) How much current is in a 60-W light bulb connected to 120 V?
A) 0.25 A
B) 0.5 A
C) 2 A
D) 4 A
E) more than 4 A
Answer: B
4) The current in a 100-W bulb connected to a 120-V source is
A) 0.5 A.
B) 1.2 A.
C) 12,000 A.
D) none of the above
Answer: D
5) What is the power rating of a device that draws 0.8 A when connected to 120 V?
A) 12 W
B) 15 W
C) 60 W
D) 96 W
E) 120 W
Answer: D
6) 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
Answer: C
7) A pair of 60-W and 100-W incandescent lamps are intended for 120-V operation. Which lamp
has a larger resistance?
A) 60-W lamp
B) 100-W lamp
C) both the same
Answer: A
8) A pair of 60-W and 100-W incandescent lamps are intended for 120-V operation. Which lamp
draws more current?
A) 60-W lamp
B) 100-W lamp
C) both the same
Answer: B
9) A 100-W lamp glows brighter than a 25-W lamp. The electric resistance of the 100-W lamp is
A) less.
B) greater.
C) the same.
Answer: A
10) A compact fluorescent lamp gives more light output for
A) less power.
B) the same power.
C) greater resistance.
Answer: A
11) Which of these lamps is the longer lasting in a common circuit?
A) incandescent lamp
B) compact fluorescent lamp
C) light-emitting diode
D) all about the same
Answer: C
12) An electric heater is rated at 300 W when used in a 110-V circuit. The safety fuse in the
circuit can accommodate 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
Answer: D
13) A certain bulb with a resistance of 95 ohms and labeled "150 W" is designated for use in a
A) 120-V circuit.
B) 240-V circuit.
C) either
D) not enough information
Answer: A
14) A heater uses 20 A when used in a 110-V line. If electric power costs 10 cents per kilowatt
hour, the cost of operating the heater for 10 hours is
A) $0.22.
B) $0.55.
C) $2.20.
D) $5.50.
E) none of the above
Answer: C
15) A power line with a resistance of 2 ohms draws a current of 80 A. The power dissipated in
the line is
A) 40 W.
B) 160 W.
C) 320 W.
D) 12,800 W.
E) none of the above
Answer: D
16) 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 the above
Answer: E
17) Which has the thicker lamp filament, a 60-W incandescent bulb or a 100-W incandescent
bulb?
Answer: The 100-W bulb has less resistance and a thicker lamp filament, for it draws more
current. This is consistent with the power relationship: P = IV. More current I for the same
voltage V means less resistance. (It is important to note that both watts and volts are printed on a
light bulb. A bulb that is labeled "100 W/120V" is 100-W only if there is 120-V across it. If there
is only 110-V across it, then the power output is only 84-W!)
18) A 60-W bulb and a 100-W bulb are connected in series in a circuit. Which draws more
current? Which draws more current when connected in parallel?
Answer: Both bulbs connected in series have the same current, as is characteristic of any series
circuit. When the bulbs are connected in parallel, voltage across each is the same and current
depends on resistance. The 100-W bulb has less resistance, so therefore more current. That's why
it's brighter for the same voltage.
Test Bank for Conceptual Physical Science
Paul Hewitt, John Suchocki, Leslie Hewitt
9780321752932, 9780134060491
