Physics Chapter 7

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

A

Alternating current is normally produced by a (A) generator. (B) battery. (C) both of the above (D) none of the above

A

Between a kilowatt and a kilowatt-hour, which is a unit of energy and which is a unit of power? (A) A kilowatt is a unit of power and a kilowatt-hour is a unit of energy. (B) Both kilowatt and kilowatt-hour are the units of power. (C) Both kilowatt and kilowatt-hour are the units of energy. (D) A kilowatt is a unit of energy and a kilowatt-hour is a unit of power.

A

Coulomb's law is most similar to (A) Newton's law of gravity. (B) the law of conservation of energy. (C) the law of electric potential. (D) Archimedes' laws of hydrostatics.

A

How are magnetic poles different from electric charges? (A) Electric charges can be isolated, magnetic poles cannot. (B) Magnetic poles can be isolated, electric charges cannot. (C) Opposite magnetic poles attract and likes repel; opposite electric charges repel and likes attract. (D) Opposite electric charges attract and likes repel; opposite magnetic poles repel and likes attract.

A

How does the sum of the currents through the branches of a simple parallel circuit compare with the current that flows through the voltage source? (A) The sum of currents though parallel branches equals the current through the source. (B) The sum of currents though parallel branches is equal to the current through the source divided by the number of branches. (C) There is not enough information in the question. (D) The sum of currents though parallel branches is equal to the current through the source multiplied by the number of branches.

A

How is Coulomb's law different from Newton's law of gravity? (A) Electrical forces may be either attractive or repulsive, whereas gravitational forces are only attractive. (B) Newton's law of gravity is an inverse-square law, but Coulomb's law is not. (C) Coulomb's law is an inverse-square law, but Newton's law of gravity is not. (D) Gravitational forces may be either attractive or repulsive, whereas electrical forces are only attractive.

A

How is the rule for the interaction between magnetic poles similar to the rule for the interaction between electric charges? (A) In both interactions, opposites attract and likes repel. (B) Magnetic poles and electric charges can only repel. (C) In both interactions, opposites repel and likes attract. (D) Magnetic poles and electric charges can only attract.

A

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

A

Strip electrons from an atom and the atom becomes a (A) positive ion. (B) negative ion. (C) different element.

A

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

A

The source of a magnetic field is a moving (A) electron. (B) magnetic north pole only. (C) magnetic north or south pole. (D) magnetic south pole only.

A

The source of all magnetism is (A) moving electric charge. (B) tiny domains of aligned atoms. (C) tiny pieces of iron. (D) ferromagnetic materials. (E) none of the above

A

The term for a current that moves in one direction is (A) direct current, dc. (B) dc or ac. (C) rarely used, because it is unusual in practice. (D) alternating current, ac.

A

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

A

What condition is necessary for a sustained flow of electric charge through a conducting medium? (A) A sustained flow of electric charge requires a device to maintain a difference in electric potential. (B) A sustained flow of electric charge requires a device to maintain a difference in pressure. (C) A sustained flow of electric charge requires a difference in pressure at the initial moment of time. No special measures are needed to maintain it at the further moments of time. (D) A sustained flow of electric charge requires a difference in electric potential at the initial moment of time. No special measures are needed to maintain it at the further moments of time. (E) A sustained flow of electric charge requires a device to keep the electric potential equal throughout the medium.

A

What condition is necessary for heat energy to flow from one end of a metal bar to another? (A) Temperature difference. The heat flows from the end with higher temperature to the end with lower temperature. (B) Temperature difference. The heat flows from the end with lower temperature to the end with higher temperature. (C) Pressure difference. The heat flows from the end with higher pressure to the end with lower pressure. (D) Pressure difference. The heat flows from the end with lower pressure to the end with higher pressure. (E) Electrical potential difference. The heat flows from the end with higher potential to the end with lower potential. (F) Electrical potential difference. The heat flows from the end with lower potential to the end with higher potential.

A

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

A

Which has more resistance − a short wire or a long wire of the same thickness and made from the same material? (A) Long wire (B) Short wire (C) Both wires have the same resistance.

A

Which part of an atom is positively charged, and which part is negatively charged? (A) The proton has a positive charge and the electron has a negative charge. (B) The neutron has a positive charge and the proton has a negative charge. (C) The neutron has a positive charge and the electron has a negative charge. (D) The proton has a positive charge and the neutron has a negative charge. (E) The electron has a positive charge and the proton has a negative charge. (F) The electron has a positive charge and the neutron has a negative charge.

A

Which pole of a compass needle points to a south pole of magnet? (A) north pole. (B) south pole. (C) both of the above

A

An ampere is a unit of electrical (A) pressure. (B) current. (C) resistance. (D) all of the above (E) none of the above

B

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

B

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) relatively small. (B) equally huge. (C) not enough information given

B

Distinguish between DC and AC. (A) AC is an electric current that flows in one direction only; DC is an electric current that repeatedly reverses its direction. (B) DC is an electric current that flows in one direction only; AC is an electric current that repeatedly reverses its direction. (C) DC is a flow of positively charged particles; AC is a flow of negatively charged particles. (D) AC is a flow of positively charged particles; DC is a flow of negatively charged particles.

B

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

B

How is Coulomb's law similar to Newton's law of gravity? (A) Electrical forces and gravitational forces may be either attractive or repulsive. (B) Coulomb's law and Newton's law of gravity are the inverse-square laws. (C) Coulomb's law and Newton's law of gravity are the inverse-cube laws. (D) Electrical forces and gravitational forces are only attractive.

B

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

B

In an electrically neutral atom the number of protons in the nucleus is equal to the number of (A) neutrons in the nucleus. (B) electrons that surround the nucleus. (C) both of the above (D) none of the above

B

Magnet A has twice the magnetic field strength of magnet B, and at a certain distance pulls on magnet B with a force of 100 N. The amount of force that magnet A exerts on magnet B is (A) at or about 50 N. (B) exactly 100 N. (C) not enough information given

B

Rub electrons from your hair with a comb and the comb becomes (A) positively charged. (B) negatively charged.

B

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

B

The fundamental force underlying all chemical reactions is (A) centripetal. (B) electrical. (C) gravitational. (D) nuclear. (E) none of the above

B

What is induced by the rapid alternation of an electric field? (A) An electric charge is induced in any region of space in which an electric field is changing with time. (B) A magnetic field is induced in any region of space in which an electric field is changing with time. (C) An electric current is induced in any region of space in which an electric field is changing with time. (D) Magnetic poles are induced in any region of space in which an electric field is changing with time.

B

What is it called when it is calibrated to read current? (A) Voltmeter (B) Ammeter (C) Ohmmeter (D) Wattmeter

B

What is it called when it is calibrated to read voltage? (A) Wattmeter (B) Voltmeter (C) Ammeter (D) Ohmmeter

B

What is the unit of electrical resistance? (A) Ampere (A) (B) Ohm (Ω) (C) Volt (V) (D) Coulomb (C)

B

What kind of materials are the best conductors? Why are they so good at conducting electricity? (A) Metals are the best conductors because their electrons are tightly bound to nuclei and belong to particular atoms. (B) Metals are the best conductors because their atoms have one or more outer electrons that are loosely bound to their nuclei. (C) Glass and rubber are the best conductors because their electrons are tightly bound to nuclei and belong to particular atoms. (D)Glass and rubber are the best conductors because their atoms have one or more outer electrons that are loosely bound to their nuclei.

B

What produces a magnetic field? (A) A magnetic field is produced by moving mass. (B) A magnetic field is produced by moving electric charges. (C) A magnetic field surrounds any electrically charged object. (D) Every mass is surrounded by a gravitational field.

B

A material that falls into the midrange of conductivity, since it possess few electrons that are free to move is a/an (A) superconductor. (B) conductor. (C) semiconductor. (D) insulator.

C

A material with a lot of free charged particles that easily flow through it when an electrical force acts on them is a/an (A) superconductor. (B) semiconductor. (C) conductor. (D) insulator.

C

A material with very little or no free charged particles and through which current does not easily flow is a/an (A) semiconductor. (B) conductor. (C) insulator. (D) superconductor.

C

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

C

Magnetism is due to the motion of electrons as they (A) move around the nucleus. (B) spin on their axes. (C) both of the above (D) none of the above

C

Surrounding every moving electron is (A) a magnetic field. (B) an electric field. (C) both of the above (D) none of the above

C

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

C

The intensity of cosmic rays bombarding Earth's surface is largest at the (A) equator. (B) midlatitudes. (C) poles.

C

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

C

The units used to measure electrical resistance are called (A) watts. (B) AC. (C) ohms. (D) volts.

C

What is meant by saying that charge is conserved? (A) Charge cannot be transferred; it can be created or destroyed. (B) Charge cannot be created; it can be transferred or destroyed. (C) Charge cannot be created or destroyed; it can only be transferred. (D) Charge cannot be destroyed or transferred; it can only be created.

C

When a 10-V battery is connected to a resistor, 2 A of current flow in the resistor. What is the resistor's value? (A) more than 20 ohms (B) 2 ohms (C) 5 ohms (D) 10 ohms (E) 20 ohms

C

Which has more resistance − a thick wire or a thin wire of the same length and made from the same material? (A) Both wires have the same resistance. (B) Thick wire (C) Thin wire

C

Which type of circuit is favored for operating several electrical devices, each independently of the other − series or parallel? Defend your answer. (A) Parallel circuit is better because through each device always passes the same current. (B) Series circuit is better because turning off a device doesn't affect the other devices. (C) Parallel circuit is better because turning off a device doesn't affect the other devices. (D) Series circuit is better because each device in circuit always has the same voltage.

C

A likely cause for the existence of Earth's magnetic field is (A) convection currents in the liquid part of Earth's core. (B) great numbers of very slow moving charges in the Earth. (C) moving charges in the liquid part of Earth's core. (D) all of the above (E) none of the above

D

Voltage can be induced in a wire by (A) changing the current in a nearby wire. (B) moving the wire near a magnet. (C) moving a magnet near the wire. (D) all of the above (E) none of the above

D

What is a galvanometer? (A) A galvanometer is a device that indicates electrical charge. (B) A galvanometer is a device that measures magnetic field. (C) A galvanometer is a device that measures electric field. (D) A galvanometer is a device that indicates electric current.

D

What is induced by the rapid alternation of a magnetic field? (A) An electric current is induced in any region of space in which a magnetic field is changing with time. (B) Magnetic poles are induced in any region of space in which a magnetic field is changing with time. (C) An electric charge is induced in any region of space in which a magnetic field is changing with time. (D) An electric field is induced in any region of space in which a magnetic field is changing with time.

D

When the filament breaks in one lightbulb in a series circuit, other bulbs in the circuit normally (A) continue glowing, but dimly. (B) absorb energy from the damaged bulb. (C) continue glowing as brightly. (D) go out.

D

Why is iron magnetic and wood is not? (A) Wood has magnetic domains; iron does not. (B) Wood has loose electrons; iron does not. (C) Iron has loose electrons; wood does not. (D) Iron has magnetic domains; wood does not.

D

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

E

What condition is necessary for electric charge to flow from one end of a metal bar to another? (A) Pressure difference. The electric charge flows from the end with higher pressure to the end with lower pressure. (B) Temperature difference. The electric charge flows from the end with higher temperature to the end with lower temperature. (C) Pressure difference. The electric charge flows from the end with lower pressure to the end with higher pressure. (D) Electrical potential difference. The electric charge flows from the end with lower potential to the end with higher potential. (E) Electrical potential difference. The electric charge flows from the end with higher potential to the end with lower potential. (F) Temperature difference. The electric charge flows from the end with lower temperature to the end with higher temperature.

E

Why do electrons, rather than protons, make up the flow of charge in a metal wire? (A) Protons are loosely attached to atomic nuclei; electrons are locked in the atomic nuclei. (B) Protons are much smaller than electrons. (C) Electrons have an electric charge; protons have no charge. (D) Electrons are much smaller than protons. (E) Electrons are loosely attached to atomic nuclei; protons are locked in the atomic nuclei.

E