Deck 22: Electric Force and the Electric Charge

Question 1

The electrostatic force between two charges is similar to the gravitational force between two masses, based on all of the following features except for

A) the force depends on the product of the entities.
B) the force is inversely proportional to the square of the distance between the two entities.
C) the proportionality constant is independent of the magnitude of the entities.
D) There is no exception: All of the above are true.
E) None of the above is true.

Answer 1

There is no exception: All of the above are true.

Question 2

The electrostatic force between two charges

A) is responsible for solids holding together and not crumbling into many tiny pieces.
B) increases as the distance between the charges decreases.
C) is attractive.
D) All of the above are true.
E) None of the above is true.

Answer 2

increases as the distance between the charges decreases.

Question 3

When an electron and a proton are separated by a distance d, they experience an electrostatic force F. A second electron is placed very close to the proton so that the electron-proton separation distance is much smaller than d. The magnitude of the force on the first electron is

A) 0
B) F/2.
C) F
D) 2F.
E) unknown; more information is needed to work out the answer.

Answer 3

0

Question 4

Two conducting spheres attract each other. The following statement is true:

A) At least one sphere is charged.
B) The spheres must be positively charged.
C) The spheres must be negatively charged.
D) The spheres must have opposite charges.
E) Both spheres must be charged.

Question 5

Two conducting spheres repel each other. The following statement is true:

A) At least one sphere is charged.
B) The spheres must be positively charged.
C) The spheres must be negatively charged.
D) The spheres must have opposite charges.

Question 6

The unit of charge, coulomb, is defined in terms of the force between

A) two electrons.
B) two protons.
C) an electron and a proton.
D) none of the above: The unit of charge is not defined in terms of the force between any two charges at rest.

Question 7

The magnitude of the force experienced by a 10.0-nC charge acting on itself is

A) zero.
B) infinity.
C) a finite value.
D) not defined.

Question 8

The electrostatic force between two protons separated by a distance d is

A) larger than the gravitational force between the same two protons.
B) approximately the same as the gravitational force between the same two protons.
C) less than the gravitational force between the same two protons.
D) unknown; more information is needed to work out the answer.

Question 9

As the distance between two protons increases, the ratio of the electrostatic to the gravitational forces experienced by the protons

A) increases.
B) decreases.
C) remains the same.
D) is unknown; more information is needed to work out the answer.

Question 10

Two charges, q₁ larger than q₂, are attracted by each other. The magnitude of the force on charge q₁ due to charge q₂ is

A) larger than the force on charge q₂ due to charge q₁.
B) the same as the force on charge q₂ due to charge q₁.
C) smaller than the force on charge q₂ due to charge q₁.
D) unknown; more information is needed to work out the answer.

Question 11

Coulomb's torsional balance is used in experiments intended to verify

A) the existence of electric charge.
B) that charge comes in negative and positive "flavors."
C) that unlike charges attract.
D) that the force between charges is an inverse-square force.

Question 12

To determine its charge, an oil drop is suspended motionless between two parallel plates that provide an electrostatic force acting on it. The following statement is true:

A) The oil drop has the same number of electrons as protons.
B) The oil drop is electrostatically neutral.
C) The weight of the drop is negligible.
D) The electrostatic force acting on the drop has the same magnitude as the weight of the drop, but points in the opposite direction.
E) None of the above is correct.

Question 13

A hydrogen atom consists of an electron orbiting a nucleus made of a single proton. The electrostatic force between the two is 2.3 * 10³⁹ times greater than the gravitational force. If we could adjust the separation between the two particles, the distance at which the electrostatic and gravitational forces would be equal is

A) 2.3* 10³⁹ m.
B) 0.47 * 10²⁰ m.
C) 0.21 * 10^-20 m.
D) 0.43 * 10^-39 m.
E) none of the above; the electrostatic and the gravitational forces acting between the two can never be equal.

Question 14

An atomic nucleus has a charge of +40e. The force on an electron placed 1.5 *10^-9 m from the nucleus is

A) 60 *10^-9 N.
B) 26 * 10^-9 N.
C) 4.1 *10^-9 N.
D) 26* 10⁹ N.
E) 60 * 10⁹ N.

Question 15

Two charges -2q and -q are placed a distance a apart. A third charge -q is placed so that the force on it is zero. The third charge

A) cannot be placed on the line joining the first two charges.
B) must be placed on the line joining the first two charges, between the charges, and closer to -2q.
C) must be placed on the line joining the first two charges, between the charges, and closer to -q.
D) must be placed on the line joining the first two charges, not between the charges, and on the -2q charge side.
E) must be placed on the line joining the first two charges, not between the charges, and on the -q charge side.

Question 16

Charge +q is placed at -a, and charge -2q is placed at 2a along the x axis. A third charge -3q is placed on the x axis so that the force on it is zero. The coordinate of the third charge is

A) -8.1a.
B) -10.58a.
C) 1.2a.
D) 0.58a.
E) 8.1a.

Question 17

Charges +q and -3q, when placed a distance a apart, experience an electrostatic force F. Charges -2q and +q, when placed a distance 2a apart, experience an electrostatic force that is

A) larger than F.
B) the same as F.
C) smaller than F.
D) unknown; more information is needed to work out the answer.

Question 18

Two charges repel each other with a force F. When the distance between the charges is halved, the force they experience is

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

Question 19

Charge q experiences a repulsive force of 0.50 mN when placed at a distance of 25 cm from charge q₁, and it experiences an attractive force of 0.25 mN when placed a distance of 75 cm from charge q₂. The ratio q₁/ q₂ is

A) 2/9.
B) 2/3.
C) 9/2.
D) 6.
E) 18.

Question 20

Three charges (-q, +q, and Q) are placed at the vertices of an equilateral triangle. The force on Q due to the charges -q and +q

A) points in the positive x direction.
B) points in the positive y direction.
C) is zero.
D) points in the negative x direction.
E) points in the negative y direction.

Question 21

Three charges (-q, +q, and Q) are placed at the vertices of an equilateral triangle. The force on Q due to the charges -q and +q

A) points in the positive x direction.
B) points in the positive y direction.
C) is zero.
D) points in the negative x direction.
E) points in the negative y direction.

Question 22

Charges are placed at the corners of a square whose sides are 2.0 m in length. The charges are +4.0 nC at (0, 0), +3.0 nC at (2.0, 0), -3.0 nC at (0, 2.0), and +4.0 nC at (2.0, 2.0). The magnitude of the force exerted on a +1.0-nC test charge placed at the square's center is

A) 0 N.
B) 4.5 *10^-9 N.
C) 27*10^-9 N.
D) 32 * 10^-9 N.
E) 45 * 10^-9 N.

Question 23

Two spheres of mass 3.0 g, identical in shape and made of the same material, are suspended from the same point by massless strings of length L, much larger than the radius of the spheres. When the spheres are charged with 4.0 nC and 5.0 nC respectively, the angle made by the 4.0-nC charge with the vertical is

A) larger than the angle made by the 5.0 nC charge with the vertical.
B) the same as the angle made by the 5.0 nC charge, and nonzero.
C) the same as the angle made by the 5.0 nC charge, and zero.
D) smaller than the angle made by the 5.0 nC charge with the vertical.

Question 24

Two spheres of mass 3.0 g, identical in shape and made of the same material, are suspended from the same point by massless strings of length 1.0 m, much larger than the radius of the spheres. When one of the spheres is charged with 4.0 nC, the angle made by it with the vertical is 5.0^o. The charge on the second sphere is

A) 2.2 $\mu$ C.
B) 4.0 $\mu$ C.
C) 2.2 nC.
D) 4.0 nC.

Question 25

Two spheres of mass 3.0 g, identical in shape and made of the same material, are suspended from the same point by massless strings of length 1.0 m, much larger than the radius of the spheres. When one of the spheres is charged with 4.0 nC, the angle made by it with the vertical is 15.0^o. The tension in the string is

A) 7.6 mN.
B) 28 mN.
C) 29 mN.
D) 31 mN.
E) 0.11 N.

Question 26

The magnitude of the charge on a proton is

A) the same as the magnitude of the charge on an electron.
B) smaller than the magnitude of the charge on an electron.
C) greater than the magnitude of the charge on an electron.

Question 27

Charge quantization implies that

A) the difference between the charge on any two bodies is never less than one electron charge.
B) no body can have a charge with a magnitude smaller than one electron charge.
C) the charge of any charged body is an integer multiple of one electron charge.
D) all of the above are true.
E) none of the above is true.

Question 28

Charge is conserved in all of the following except in

A) chemical reactions.
B) electrostatic induction.
C) processes of electrostatic generation.
D) lightning storms.
E) all of the above.

Question 29

The charge on 2.0 kg of protons is

A) 1.9 * 10⁸ C.
B) 3.2 *10⁸C.
C) 0.80 * 10^-19C.
D) 3.2 *10^-19C.
E) 1.9 * 10^-19C.

Question 30

To charge a sphere with +640 nC, the number of electrons transferred to the sphere is

A) 8.00 * 10⁸.
B) 4.00 * 10⁸.
C) none.
D) -4.00 * 10⁸.
E) -8.00 * 10⁸.

Question 31

An oil drop has a charge of 8.0 $\times$ 10^-19 C. The number of excess electrons on the oil drop is

A) 2.
B) 5.
C) 8.
D) 13.

Question 32

A piece of plastic has a net charge of +4.00 nC. The number of protons in excess of the number of electrons on the piece of plastic is

A) 4.0 F*10^-9.
B) 6.4 *10^-19.
C) 6.4 * 10^-28.
D) 2.5 * 10^-28.
E) 2.5 *10¹⁰.

Question 33

The charge on an antiparticle is

A) negative.
B) zero.
C) positive.
D) the negative of the charge of the corresponding particle.

Question 34

Materials in which the electrons are loosely bound to the nuclei are referred to as

A) conductors.
B) superconductors.
C) semiconductors.
D) inductors.
E) insulators.

Question 35

The sign of the charge acquired by a body is

A) the same as the sign of the charge on the charging body if conduction or induction is the charging process.
B) the opposite of the sign of the charge on the charging body if conduction or induction is the charging process.
C) the same as the sign of the charge on the charging body if conduction is the charging process, and the opposite if induction is the charging process.
D) the opposite of the sign of the charge on the charging body if conduction is the charging process, and the same if induction is the charging process.

Question 36

Body A is charged by friction, then is used in charging B by conduction. In the latter process, body A

A) decreases the magnitude of its charge.
B) increases the magnitude of its charge.
C) does not experience a change in the magnitude of its charge.
D) More information is needed to work out the answer.

Question 37

Body A is charged by friction, then is used in charging B by simple induction. In the latter process, body A

A) decreases the magnitude of its charge.
B) increases the magnitude of its charge.
C) does not experience a change in the magnitude of its charge.
D) More information is needed to work out the answer.

Question 38

Two spheres made of conducting materials are placed near (but not touching) each other on an insulated table. Sphere A carries a net charge and sphere B is neutral. The statement that best describes the electrostatic force between the spheres is

A) the force is attractive if A is positively charged, and repulsive if A is negatively charged.
B) the force is repulsive irrespective of the charge on A.
C) the force is attractive irrespective of the charge on A.
D) there is no electrostatic force because B is neutral.

Question 39

Two spheres made of nonconducting materials are placed near (but not touching) each other on an insulated table. Sphere A carries a net charge and sphere B is neutral. The statement that best describes the electrostatic force between the spheres is

A) the force is attractive if A is positively charged and repulsive if A is negatively charged.
B) the force is repulsive irrespective of the charge on A.
C) the force is attractive irrespective of the charge on A.
D) there is no electrostatic force because B is neutral.

Question 40

Two spheres are placed near (but not touching) each other on an insulated table. Sphere A is made of a nonconducting material and carries a net charge, while sphere B is made of a conducting material and is neutral. The statement that best describes the electrostatic force between the spheres is

A) the force is attractive if A is positively charged, and repulsive if A is negatively charged.
B) the force is repulsive irrespective of the charge on A.
C) the force is attractive irrespective of the charge on A.
D) there is no electrostatic force since B is neutral.

Question 41

Two nonconductive spheres are placed near (but not touching) each other on an insulated table. Sphere A carries a net negative charge, while sphere B is neutral. Sphere B is briefly touched with a wire that is grounded. Sphere B

A) becomes positively charged.
B) remains neutral.
C) becomes negatively charged.

Question 42

Two conductive spheres are placed near (but not touching) each other on an insulated table. Sphere A carries a net negative charge, while sphere B is neutral. Sphere B is briefly touched with a wire that is grounded. Sphere B

A) becomes positively charged.
B) remains neutral.
C) becomes negatively charged.

Question 43

Two conductive, uncharged spheres are touching each other on an insulated table. Sphere A is briefly touched with a positively charged rod, and then the spheres are separated. Sphere B

A) becomes positively charged.
B) remains neutral.
C) becomes negatively charged.

Question 44

Two conductive, uncharged spheres are touching each other on an insulated table. A positively charged nonconductive rod is brought in the vicinity of sphere A, not touching it, and then the spheres are separated. Sphere A

A) becomes positively charged.
B) remains neutral.
C) becomes negatively charged.

Question 45

Two conductive, uncharged spheres are touching each other on an insulated table. A positively charged nonconductive rod is brought in the vicinity of sphere A, not touching it, and then the spheres are separated. Sphere B

A) becomes positively charged.
B) remains neutral.
C) becomes negatively charged.

Question 46

Two small, identical, neutral iron spheres each have a mass of 20.0 g. A quantity of 5.0 *10¹⁰ electrons are transferred from one sphere to the other so that the attractive electrostatic force between the spheres becomes equal to the weight of one sphere. The separation between the spheres is

A) 2.3* 10²¹ m.
B) 1.1 * 10²¹ m.
C) 1.7 * 10^-3 m.
D) 1.1 * 10¹⁶ m.
E) 2.3 *10¹⁶ m.

Question 47

On dry days we tend to have more trouble with static electricity buildup than on humid days. Why?

A) On humid days the strong nuclear forces are larger, so they lose fewer charges at once (get shocked) than on dry days.
B) On humid days the many water molecules in the air pick up excess charge little by little, whereas on dry days there are fewer water molecules in the air, so we accumulate charge and get discharged only when we touch something and lose more charges at once (get shocked).
C) A charged object is always attracted or repelled by another charged object.
D) Water is a better insulator than air.

Question 48

As a neutrally charged person walks across a wool carpet, his leather-soled shoes lose electrons to the carpet. With every step the person becomes more and more positively charged. When the person gets near the metal knob of the door he will

A) attract charges from the door; the transfer of protons from the knob to the person will occur in the form of a spark.
B) attract charges from the door; the transfer of electrons from the knob to the person will occur in the form of a spark.
C) repel the charges on the door; the transfer of protons from the person to the knob will occur in the form of a spark.
D) repel the charges on the door; the transfer of electrons from the person to the knob will occur in the form of a spark.