Deck 6: Electricity and Magnetism

Question 1

Superconductivity occurs in certain substances

A)only at very low temperatures.
B)only at very high temperatures.
C)at all temperatures.
D)only when they are in the liquid state.

Answer 1

only at very low temperatures.

Question 2

A positive electric charge

A)attracts other positive charges.
B)repels other positive charges.
C)does not interact with other positive charges but only with negative ones.
D)consists of an excess of electrons.

Answer 2

repels other positive charges.

Question 3

Protons and electrons have different masses.When they are the same distance apart, the electric force between two electrons

A)is less than the force between two protons.
B)is the same as the force between two protons.
C)is greater than the force between two protons.
D)Any of these choices could be correct, depending on the distance between each pair of particles.

Answer 3

is the same as the force between two protons.

Question 4

Relative to the electric force between two protons, the gravitational force between them is

A)weaker.
B)equal in magnitude.
C)stronger.
D)Any of these choices could be correct, depending on how far apart the protons are.

Question 5

The charge on an electron

A)is l C.
B)depends on the electron's mass.
C)depends on the electron's size.
D)is always the same.

Question 6

A kilowatt hour is a unit of

A)energy.
B)power.
C)potential difference.
D)electric charge.

Question 7

Superconductors

A)have no electrical resistance.
B)have very little electrical resistance.
C)are used in making transistors.
D)have no practical applications.

Question 8

The particle easiest to remove from an atom is a(an)

A)electron.
B)proton.
C)neutron.
D)nucleus.

Question 9

When a rubber rod is stroked with a piece of fur,

A)the rod becomes negatively charged while the fur remains neutral.
B)both the rod and fur become negatively charged.
C)the rod becomes negatively charged and the fur becomes positively charged.
D)Any of these choices could be correct, depending on how hard the rod is stroked.

Question 10

A molecule that has lost an electron becomes a

A)positive ion.
B)negative ion.
C)nucleus.
D)superconductor.

Question 11

An object has a positive electric charge whenever

A)it has an excess of electrons.
B)it has a deficiency of electrons.
C)the nuclei of its atoms are positively charged.
D)the electrons of its atoms are positively charged.

Question 12

Coulomb's formula F = KQ₁Q₂/R² gives the force between two charges in free space.The value of K

A)is the same under all circumstances.
B)is different for positive and negative charges.
C)depends on the masses of the charged particles.
D)equals the charge on the electron.

Question 13

Which of the following is not a basic physical law or phenomenon but applies only to certain materials?

A)Coulomb's law
B)Ohm's law
C)the motor effect
D)electromagnetic induction

Question 14

When the voltage across a certain resistance is V, the power delivered is P.If the voltage is doubled to 2V, the power delivered becomes

A)2P.
B)4P.
C)P².
D)4P².

Question 15

Which of the following statements is not true?

A)Protons are positively charged.
B)The proton mass is greater than the electron mass.
C)The proton mass is almost the same as the neutron mass.
D)A proton in an atom circulates around its nucleus.

Question 16

A solid conductor is one

A)whose electrons are firmly bound in place.
B)whose electrons are free to move about.
C)that has no electrons.
D)that has too many electrons.

Question 17

An atom consists of a

A)uniform distribution of positive charge in which electrons are embedded.
B)uniform distribution of negative charge in which electrons are embedded.
C)small negative nucleus surrounded at a distance by protons.
D)small positive nucleus surrounded at a distance by electrons.

Question 18

The conventional unit of battery capacity is the ampere-hour, which is actually a unit of

A)energy.
B)power.
C)potential difference.
D)electric charge.

Question 19

The volt is the unit of electric

A)current.
B)potential difference.
C)potential energy.
D)resistance.

Question 20

The watt, the unit of power, is equal to the

A)(volt)(ampere).
B)volt/ampere.
C)ampere/volt.
D)(volt)(ohm).

Question 21

A magnet attracts

A)all substances.
B)only iron and iron alloys and repels nothing.
C)iron and iron alloys and repels other substances.
D)some substances and repels others.

Question 22

Two charges of +Q are 1 cm apart.If one of the charges is replaced by a charge of -Q, the magnitude of the force between them is

A)zero.
B)smaller.
C)the same.
D)larger.

Question 23

A compass needle tends to

A)line up perpendicular to a magnetic field.
B)line up parallel to a magnetic field.
C)turn slowly in a constant magnetic field.
D)point only toward the North Pole.

Question 24

A current-carrying wire is in a magnetic field with the direction of the current perpendicular to that of the field.

A)The wire tends to move parallel to the field.
B)The wire tends to move perpendicular to the field.
C)The wire tends to turn until it is perpendicular to the field.
D)The wire has no tendency to move or to turn.

Question 25

A current-carrying wire is in a magnetic field with the direction of the current parallel to that of the field.

A)The wire tends to move parallel to the field.
B)The wire tends to move perpendicular to the field.
C)The wire tends to turn until it is parallel to the field.
D)The wire has no tendency to move or to turn.

Question 26

At different places on the earth's surface, the earth's magnetic field

A)is the same in direction and magnitude.
B)may be different in direction but not in magnitude.
C)may be different in magnitude but not in direction.
D)may be different in both magnitude and direction.

Question 27

The voltage needed to produce a current of 8 A in a resistance of 12 ohms is

A)0.67 V.
B)1.5 V.
C)4 V.
D)96 V.

Question 28

Direct electric current cannot be used to operate

A)electric motors.
B)electric heaters.
C)electromagnets.
D)transformers.

Question 29

Two charges repel each other with a force of 10^-6 N when they are 10 cm apart.When they are brought closer together until they are 2 cm apart, the force between them becomes

A)4 * 10^-8 N.
B)5 *10^-6 N.
C)8 * 10^-6 N.
D)2.5 * 10^-5 N.

Question 30

A current-carrying loop in a magnetic field always tends to turn until the plane of the loop is

A)parallel to the field.
B)perpendicular to the field.
C)either parallel or perpendicular, depending on the direction of the current.
D)at a 45-degree angle with the field.

Question 31

When a current passes through a resistance, the electric energy that is lost

A)becomes heat.
B)becomes magnetic energy.
C)is returned to the source of the current.
D)disappears.

Question 32

A current is flowing south along a power line.Neglecting the earth's field, the direction of the magnetic field under the power line is

A)north.
B)south.
C)east.
D)west.

Question 33

The primary coil of a transformer is connected to a source of alternating current of voltage V.The voltage of the secondary current is

A)lower than V.
B)equal to V.
C)higher than V.
D)Any of these choices could be correct, depending on the ratio of turns in the transformer coils.

Question 34

The current with which a transformer is used

A)must be dc.
B)must be ac.
C)may be either dc or ac.
D)may be neither dc nor ac.

Question 35

A charge of +Q attracts a charge of -Q 1 cm away with a force of F.Another charge of +Q is placed next to the first one.The force on the charge of -Q is now

A)F/2
B)F
C)2F
D)4F

Question 36

In a drawing of magnetic field lines, the weaker the field is, the

A)closer together the field lines are.
B)farther apart the field lines are.
C)more nearly parallel the field lines are.
D)more divergent the field lines are.

Question 37

The current in a 20-ohm electric heater operated at 240 V is

A) 0.083 A.
B) 12 A.
C) 2880 A.
D) 4800 A.

Question 38

A magnetic field does not interact with a

A)stationary electric charge.
B)moving electric charge.
C)stationary magnet.
D)moving magnet.

Question 39

When a magnetized iron bar is strongly heated, its magnetic field

A)becomes weaker.
B)becomes stronger.
C)reverses its direction.
D)is unchanged.

Question 40

Two charges, one positive and the other negative, are initially 2 cm apart and are then pulled away from each other until they are 6 cm apart.The force between them is now smaller by a factor of

A)
B)3
C)9
D)27

Question 41

The primary coil of a transformer has 200 turns and its secondary coil has 50 turns, and the current in the secondary coil is 40 A.When a 12-V alternating current is applied to the primary coil of the transformer, the secondary voltage will be

A)3 V.
B)6 V.
C)24 V.
D)48 V.

Question 42

The primary coil of a transformer has 200 turns and its secondary coil has 50 turns, and the current in the secondary coil is 40 A.If the power input of the transformer is 60 W, its power output is

A)20 W.
B)60 W.
C)180 W.
D)540 W.

Question 43

The power rating of an electric motor that draws a current of 3 A when operated at 240 V is

A)80 W.
B)720 W.
C)1080 W.
D)2160 W.

Question 44

Two 240-watt light bulbs are connected in parallel across a 120-V power line. The current in each bulb is

A) 0.5 A.
B) 1.0 A.
C) 2.0 A.
D) 4.0 A.

Question 45

The primary coil of a transformer has 200 turns and its secondary coil has 40 turns. If the current in the secondary coil is 25 A, the current in the primary coil is

A) 5 A.
B) 6.4 A.
C) 2.5 A.
D) 125 A.

Question 46

Three 12-V batteries cannot be connected to give a voltage for the set of

A)6 V.
B)12 V.
C)24 V.
D)36 V.

Question 47

The current in a 24-W, 12-V light bulb is

A) 0.5 A.
B) 2 A.
C) 12 A.
D) 288 A.

Question 48

An electric iron draws a current of 15 A when connected to a 120-V power source.Its resistance is

A)0.125 ohms.
B)8 ohms.
C)16 ohms.
D)1800 ohms.

Question 49

What is the resistance in a 60-W, 12-V light bulb?

A)0.2 ohms
B)0.42 ohms
C)2.4 ohms
D)5 ohms

Question 50

The electric energy stored in a 3-V battery whose capacity is 2 Ah is

A)6 J.
B)360 J.
C)600 J.
D)21.6 kJ.