Test 5: Review A

Question 1

Which force binds atoms together to form molecules?
A) gravitational
B) centripetal
C) nuclear
D) electrical

Answer 1

*D) electrical

Question 2

A positive ion has more
A) neutrons than protons.
B) electrons than protons.
C) electrons than neutrons.
D) protons than neutrons.
E) protons than electrons.

Answer 2

*E) protons than electrons.

Question 3

To say that electric charge is quantized is to say that the charge on an object
A) is a whole-number multiple of the charge of one electron.
B) is sometimes positive.
C) will interact with neighboring electric charges.
D) can be neither created nor destroyed.
E) may occur in an infinite variety of quantities.

Answer 3

*A) is a whole-number multiple of the charge of one electron.

Question 4

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) is sometimes negative.
D) will interact with neighboring electric charges.
E) can be neither created nor destroyed

Answer 4

*E) can be neither created nor destroyed

Question 5

The unit of electric charge, the coulomb, is the charge on
A) a neutron.
B) one electron.
C) a quark.
D) a specific number of neutrons.
E) a specific large number of electrons.

Answer 5

*E) a specific large number of electrons.

Question 6

A difference between gravitational and electric forces is that electrical forces
A) attract.
B) are weaker.
C) obey the inverse-square law.
D) act over shorter distances.
E) repel or attract.

Answer 6

*E) repel or attract.

Question 7

An electron and a proton
A) attract each other.
B) repel each other.

Answer 7

*A) attract each other.

Question 8

A transistor is an example of a
A) resistor.
B) transmitter.
C) superconductor.
D) semiconductor.

Answer 8

*D) semiconductor.

Question 9

Two protons attract each other gravitationally and repel each other electrically. By far the greater force is
A) the electrical repulsion.
B) the gravitational attraction.

Answer 9

*A) the electrical repulsion.

Question 10

To say that an object is electrically polarized is to say
A) its internal electric field is zero.
B) its charges have been rearranged.
C) it is only partially conducting.
D) it is electrically charged.
E) it is to some degree magnetic.

Answer 10

*B) its charges have been rearranged.

Question 11

When a car is struck by lightning, the resulting electric field inside the car is
A) small enough to be safe for an occupant inside.
B) normally huge for a time longer than the lightning stroke itself.
C) zero.
D) normally huge, but for a brief time.

Answer 11

C) zero.

Question 12

After a capacitor is fully charged, the total number of electrons it contains
A) is much less.
B) is slightly less.
C) is much greater.
D) is slightly greater.
E) remains unchanged.

Answer 12

*E) remains unchanged.

Question 13

When the distance between two charges is halved, the electrical force between the charges
A) quadruples.
B) halves.
C) doubles.
D) is reduced by 1/4.

Answer 13

*A) quadruples.

Question 14

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

Answer 14

*A) a potential difference across its ends.

Question 15

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

Answer 15

*B) Charge flows in a closed circuit.

Question 16

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

Answer 16

*C) by interacting with an established electric field.

Question 17

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

Answer 17

*B) increases.

Question 18

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

Answer 18

*C) not at all.

Question 19

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

Answer 19

*B) generator.

Question 20

The number of electrons delivered daily to an average American home by an average power utility in the mid-1980s was
A) 110.
B) zero.
C) 220.
D) billions of billions.

Answer 20

*B) zero.

Question 21

When a 60-watt light bulb is connected to a 120-volt source the current in the light bulb is
A) 0.25 A.
B) 0.5 A.
C) 4 A.
D) 2 A.

Answer 21

*B) 0.5 A.

Question 22

Compared to the amount of electric current in the filament of a lamp, the amount of current in the connecting wire is
A) more.
B) the same.
C) always less.

Answer 22

*B) the same.

Question 23

The power dissipated in a 4-ohm resistor carrying 3 A is
A) 48 W.
B) 18 W.
C) 7 W.
D) 36 W.

Answer 23

*D) 36 W.

Question 24

The ratio of the potential difference across a metallic conductor to the current in the conductor is known as
A) conductivity.
B) resistance.
C) potential drop.
D) electromagnetic force.

Answer 24

*B) resistance.

Question 25

Moving electric charges will interact with
A) an electric field or a magnetic field.
B) only an electric field.
C) only a magnetic field.
D) none of these

Answer 25

*A) an electric field or a magnetic field.

Question 26

The source of all magnetism is
A) tiny domains of aligned atoms.
B) ferromagnetic materials.
C) tiny pieces of iron.
D) moving electric charge.

Answer 26

*D) moving electric charge.

Question 27

An iron rod becomes magnetic when
A) its electrons stop moving and point in the same direction.
B) its atoms are aligned having plus charges on one side and negative charges on the other.
C) the net spins of its electrons are in the same direction.
D) positive ions accumulate at one end and negative ions at the other end.
E) none of these

Answer 27

*C) the net spins of its electrons are in the same direction.

Question 28

Magnetic field lines about a current-carrying wire
A) circle the wire in closed loops.
B) extend radially from the wire.
C) Choices A and B are both correct.
D) None of the above choices are correct.

Answer 28

*A) circle the wire in closed loops.

Question 29

The intensity of cosmic rays bombarding the Earth’s surface is largest at the
A) equator.
B) poles.
C) mid-latitudes.

Answer 29

*B) poles.

Question 30

Compared to the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is
A) equally huge.
B) relatively small.
C) More information is needed.

Answer 30

*A) equally huge.

Question 31

Like kinds of magnetic poles repel while unlike kinds of magnetic poles
A) may attract or repel.
B) attract.
C) repel also.

Answer 31

*B) attract.

Question 31

Magnetic domains normally occur in
A) copper.
B) silver.
C) iron.
D) none of these

Answer 31

*C) iron.

Question 32

An electron is shot through a spot somewhere between the ends of a horseshoe magnet. The electron
A) is attracted to one of the poles and repelled by the other.
B) is unaffected by the field.
C) speed is increased.
D) is repelled by both poles, and therefore is turned back.
E) direction is changed.

Answer 32

*E) direction is changed.

Question 33

When a bar magnet is broken in two, each half is
A) stronger than the original magnet.
B) at most half as strong as the original magnet.
C) as magnetic as the original magnet.
D) no longer magnetic.

Answer 33

*B) at most half as strong as the original magnet.

Question 34

Superconducting electromagnets
A) may be possible in the distant future.
B) exist now.
C) may be possible soon.
D) are science fiction.

Answer 34

*B) exist now.

Question 35

When there is a change in the magnetic field in a closed loop of wire
A) electromagnetic induction occurs.
B) a current is created in the loop of wire.
C) a voltage is induced in the wire.
D) all of these
E) none of these

Answer 35

*D) all of these

Question 36

Thrust a magnet into a coil of wire and the coil
A) becomes an electromagnet.
B) has a current in it.
C) both
D) neither of these

Answer 36

*C) both

Question 37

The magnetic field strength inside a current-carrying coil will be greater if the coil encloses a
A) rod of iron.
B) wooden rod.
C) glass rod.
D) vacuum.

Answer 37

*A) rod of iron.

Question 38

If a magnet is pushed into a coil, voltage is induced across the coil. If the same magnet is pushed into a coil with twice the number of loops,
A) four times as much voltage is induced.
B) one half as much voltage is induced.
C) twice as much voltage is induced.
D) the same voltage is induced.
E) none of these

Answer 38

*C) twice as much voltage is induced.

Question 39

A transformer transforms
A) magnetic field lines.
B) generators into motors.
C) non-safe forms of energy to safe forms of energy.
D) voltage.
E) All of the above choices are correct.

Answer 39

*D) voltage.

Question 40

An electric motor is very similar to
A) a radio receiver.
B) an automobile battery.
C) an electric generator.
D) None of the above choices are correct.

Answer 40

*C) an electric generator.

Question 41

Transformers use ac so there will be the required
A) magnetic field intensities.
B) transfer of energy from coil to coil.
C) change in magnetic field for operation.
D) voltage for transformation.

Answer 41

*C) change in magnetic field for operation.

Question 42

Compared to the primary voltage, the secondary voltage may be
A) the same.
B) smaller.
C) larger.
D) larger, smaller, or the same.

Answer 42

*D) larger, smaller, or the same.

Question 42

The output power of an ideal transformer is
A) greater than the input power.
B) smaller than the input power.
C) equal to the input power.
D) may be any of these

Answer 42

*C) equal to the input power.

Question 43

Disconnect a small-voltage battery from a coil of many loops of wire and a large voltage is produced by
A) the collapse in the magnetic field.
B) latent energy in the battery.
C) the electric field between the battery terminals.
D) electrons already in the wire.

Answer 43

*A) the collapse in the magnetic field.

Question 44

Rapid change of a magnetic field induces
A) an electric field.
B) a magnetic field of greater magnitude.
C) a magnetic field of the same magnitude.

Answer 44

*A) an electric field.

Question 45

A certain transformer doubles input voltage. If the primary coil has 10 A of current, then the current in the secondary coil is
A) 2 A.
B) 10 A.
C) 5 A.
D) 25 A.
E) none of these

Answer 45

*C) 5 A.

Question 46

Metal detectors, like the ones used at airports, are activated by
A) electromagnetic induction.
B) electric fields.
C) magnetic fields.
D) alternating current.

Answer 46

*A) electromagnetic induction.

Question 47

The principal advantage of ac power over dc power is that
A) more energy is dissipated during transmission.
B) ac circuits multiply power more easily.
C) ac voltage can be transformed via conventional transformers.
D) ac circuits are safer.

Answer 47

*C) ac voltage can be transformed via conventional transformers.

Question 48

Neon signs require about 12,000 volts to operate. If the circuit uses a 120-volt power source, the ratio of primary to secondary turns on the transformer should be
A) 1:100.
B) 100:1.
C) neither of these

Answer 48

*A) 1:100.