Ch. 19

Question 1

An ion, starting from rest, accelerates from point A to point B due to a potential difference between the two points.

Does the potential energy of the ion at point B depend on the magnitude of its charge?

Answer 1

Yes

Question 2

An ion, starting from rest, accelerates from point A to point B due to a potential difference between the two points.

Does the potential energy of the ion at point B depend on its mass?

Answer 2

No

Question 3

An ion, starting from rest, accelerates from point A to point B due to a potential difference between the two points.

Does the speed of the ion at B depend on the magnitude of its charge?

Answer 3

Yes

Question 4

An ion, starting from rest, accelerates from point A to point B due to a potential difference between the two points.

Does the speed of the ion at B depend on its mass?

Answer 4

Yes

Question 5

A proton and an electron are released from rest at the midpoint between the plates of a charged parallel plate capacitor. Except for these particles, nothing else is in between the plates. Ignore the attraction between the proton and the electron, and decide which particle strikes a plate capacitor plate first.

Answer 5

The electron arrives at a plate first.

Question 6

A positive point charge and a negative point charge have equal magnitudes. One charge is fixed to a corner of a square, and the other is fixed to another corner. On which corners should the charges be placed, so that the same potential exists at the empty corners?

Answer 6

Diagonally opposite corners

Question 7

Three point charges have identical magnitudes, but two of the charges are positive and one is negative. These charges are fixed to corners of a square, one to a corner. No matter how the charges are arranged, the potential at the empty corner is always ___.

Answer 7

Positive

Question 8

Consider a spot that is located midway between two identical point charges. Which one of the following statements concerning the electric field and the electric potential at this spot is true?

Answer 8

The electric field is zero, but the electric potential is not zero.

Question 9

An electric potential energy exists when two proteins are separated by a certain distance.

Does the electric potential energy increase, decrease, or remain the same when both protons are replaced by electrons?

Answer 9

Remains the same

Question 10

An electric potential energy exists when two proteins are separated by a certain distance.

Does the electric potential energy increase, decrease, or remain the same when only one of the protons is replaced by an electron?

Answer 10

Decreases

Question 11

A proton is fixed in place. An electron is released from rest and allowed to collide with the proton. Then the roles of the proton and electron are reversed, and the same experiment is repeated. Which, if either, is traveling faster when the collision occurs, the proton or the electron?

Answer 11

The electron

Question 12

The electric potential is constant throughout a given region of space. Is the electric field zero or nonzero in this region?

Answer 12

The electric field is zero.

Question 13

In a region of space where the electric field is constant everywhere, as it is inside a parallel plate capacitor, is the potential constant everywhere?

Answer 13

No, the potential is greatest at the positive plate.

Question 14

A positive test charge is placed in an electric field. In what direction should the charge be moved relative to the field, so that the charge experiences a constant electric potential?

Answer 14

Perpendicular to the electric field

Question 15

Imagine that you are moving a positive test charge along the line between two identical point charges. With regard to the electric potential, is the midpoint on the line analogous to the top of a mountain or the bottom of a valley when the two point charges are a) positive and b) negative?

Answer 15

a) bottom of a valley

b) top of a mountain

Question 16

An empty parallel plate capacitor is connected to a battery that maintains a constant potential difference between the plates. With the battery connected, a dielectric is then inserted between the plates.

Does the electric field between the plates decrease, increase, or remain the same when the dielectric is inserted?

Answer 16

Decreases

Question 17

An empty parallel plate capacitor is connected to a battery that maintains a constant potential difference between the plates. With the battery connected, a dielectric is then inserted between the plates.

Does the capacitance decrease, increase, or remain the same when the dielectric is inserted?

Answer 17

Increases

Question 18

An empty parallel plate capacitor is connected to a battery that maintains a constant potential difference between the plates. With the battery connected, a dielectric is then inserted between the plates.

Does the charge on the plates decrease, increase, or remain the same when the dielectric is inserted?

Answer 18

Increases

Question 19

An empty parallel plate capacitor is connected to a battery that maintains a constant potential difference between the plates. With the battery connected, a dielectric is then inserted between the plates.

Does the energy stored by the capacitor decrease, increase, or remain the same when the dielectric is inserted?

Answer 19

Increases

Question 20

A parallel plate capacitor is charged up by a battery. The battery is then disconnected, but the charge remains on the plates. The plates are then pulled apart.

Does the capacitance of the capacitor decrease, increase, or remain the same as the distance between the plates increases?

Answer 20

Decreases

Question 21

A parallel plate capacitor is charged up by a battery. The battery is then disconnected, but the charge remains on the plates. The plates are then pulled apart.

Does the potential difference between the plates decrease, increase, or remain the same as the distance between the plates increases?

Answer 21

Increases

Question 22

A parallel plate capacitor is charged up by a battery. The battery is then disconnected, but the charge remains on the plates. The plates are then pulled apart.

Does the electric field between the plates decrease, increase, or remain the same as the distance between the plates increases?

Answer 22

Remains the same

Question 23

A parallel plate capacitor is charged up by a battery. The battery is then disconnected, but the charge remains on the plates. The plates are then pulled apart.

Does the electric potential energy stored by the capacitor decrease, increase, or remain the same as the distance between the plates increases?

Answer 23

Increases

Question 24

Two different charges, q1 and q2, are placed at two different locations, one charge at each location. The locations have the same electric potential V. Do the charges have the same electric potential energy?

Answer 24

No, because the electric potential energy EPE at a given location depends on the charge placed at that location as well as the electric potential V.

Question 25

Which two or more of the following actions would increase the energy stored in a parallel plate capacitor when a constant potential difference is applied across the plates?

1. Increasing the area of the plates
2. Decreasing the area of the plates
3. Increasing the separation between the plates
4. Decreasing the separation between the plates
5. Inserting a dielectric between the plates

Answer 25

1, 4, 5