16/17 MC take 2

Electrically neutral objects cannot exert an electrical force on each other, but they can exert a gravitational force on each other. A) True B) False

B

Which of the following changes will increase the capacitance of a parallel-plate capacitor? (There could be more than one correct choice.) A) increase the charge on the plates B) decrease the potential between the plates C) increase the potential between the plates D) introduce a dielectric material between the plates E) decrease the separation between the plates

D, E

As a proton moves in a direction perpendicular to the electric field lines A) it is moving from low potential to high potential and gaining electric potential energy. B) it is moving from low potential to high potential and losing electric potential energy. C) it is moving from high potential to low potential and gaining electric potential energy. D) it is moving from high potential to low potential and losing electric potential energy. E) both its electric potential and electric potential energy remain constant

E

A hydrogen atom consists of a proton and an electron. If the orbital radius of the electron increases, the electric potential energy of the electron due to the proton A) increases. B) decreases. C) remains the same. D) depends on the zero point of the potential.

A

A solid aluminum cube rests on a wooden table in a region where a uniform external electric field is directed straight upward. What can we say concerning the charge on the top surface of the cube? A) The top surface is charged positively. B) The top surface is charged negatively. C) The top surface is neutral. D) The top surface's charge cannot be determined without further information.

A

An ideal parallel-plate capacitor consists of two parallel plates of area A separated by a distance d. This capacitor is connected to a battery and charged until its plates carry charges +Q and -Q, and the battery is then disconnected. If the separation between the plates is now doubled, the electrical energy stored in the capacitor will A) double. B) quadruple. C) be cut in half. D) be cut in fourth. E) not change.

A

Two protons are fired toward each other in a particle accelerator, with only the electrostatic force acting. Which of the following statements must be true about them as they move closer together? (There could be more than one correct choice.) A) Their electric potential energy keeps increasing. B) Their kinetic energy keeps increasing. C) Their electric potential energy keeps decreasing. D) Their kinetic energy keeps decreasing. E) Their acceleration keeps decreasing.

A, D

An electron and a proton are released simultaneously from rest and start moving toward each other due to their electrostatic attraction, with no other forces present. Which of the following statements are true just before they are about to collide? (There could be more than one correct choice.) A) They are closer to the to the initial position of the electron that to the initial position of the proton. B) They are closer to the to the initial position of the proton that to the initial position of the electron. C) They are at the midpoint of their initial separation. D) They both have the same speed. E) The electrostatic force on the proton is greater than the electrostatic force on the electron.

B

The electric field at point P due to a point charge Q a distance R away from P has magnitude E. In order to double the magnitude of the field at P, you could A) double the distance to 2R. B) double the charge to 2Q. C) reduce the distance to R/2. D) reduce the distance to R/4. E) double the charge to 2Q and at the same time reduce the distance to R/2.

B

Three equal-magnitude point charges of varying signs are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square? A) A B) B C) C D) D

B

Two uncharged metal spheres, #1 and #2, are mounted on insulating support rods. A third metal sphere, carrying a positive charge, is then placed near #2. Now a copper wire is momentarily connected between #1 and #2 and then removed. Finally, sphere #3 is removed. In this final state A) spheres #1 and #2 are still uncharged. B) sphere #1 carries positive charge and #2 carries negative charge. C) sphere #1 carries negative charge and #2 carries positive charge. D) spheres #1 and #2 both carry positive charge. E) spheres #1 and #2 both carry negative charge.

B

A proton and an electron are released from rest, with only the electrostatic force acting. Which of the following statements must be true about them as they move toward each other? (There could be more than one correct choice.) A) Their electric potential energy keeps increasing. B) Their kinetic energy keeps increasing. C) Their electric potential energy keeps decreasing. D) Their kinetic energy keeps decreasing. E) Their acceleration keeps decreasing.

B, C

When a certain capacitor carries charges of ±10 µC on its plates, the potential difference cross the plates is 25 V. Which of the following statements about this capacitor are true? (There could be more than one correct choice.) A) If we double the charges on the plates to ±20 µC, the capacitance of the capacitor will also double. B) If we double the charges on the plates to ±20 µC, the potential difference across the plates will also double. C) If we double the charges on the plates to ±20 µC, the capacitance of the capacitor will not change. D) If we double the charges on the plates to ±20 µC, the potential difference across the plates will decrease by a factor of two.

B, C

Two protons are released from rest, with only the electrostatic force acting. Which of the following statements must be true about them as they move apart? (There could be more than one correct choice.) A) Their electric potential energy keeps increasing. B) Their kinetic energy keeps increasing. C) Their electric potential energy keeps decreasing. D) Their kinetic energy keeps decreasing. E) Their acceleration keeps decreasing.

B, C, E

A dielectric material such as paper is inserted between the plates of a capacitor as the capacitor holds a fixed charge on its plates. What happens to the electric field between the plates as the dielectric is inserted? A) There is no change in the field. B) The field becomes stronger. C) The field becomes weaker. D) The field reduces to zero.

C

A region of space contains a uniform electric field, directed toward the right, as shown in the figure. Which statement about this situation is correct? A) The potential at all three locations is the same. B) The potentials at points A and B are equal, and the potential at point C is higher than the potential at point A. C) The potential at points A and B are equal, and the potential at point C is lower than the potential at point A. D) The potential at point A is the highest, the potential at point B is the second highest, and the potential at point C is the lowest.

C

An ideal parallel-plate capacitor having circular plates of diameter D that are a distance d apart stores energy U when it is connected across a fixed potential difference. If you want to triple the amount of energy stored in this capacitor by changing only the size of its plates, the diameter should be changed to A) 9D. B) 3D. C) D rad3 D) D/rad3 E) D/3

C

As an electron moves in the direction the electric field lines A) it is moving from low potential to high potential and gaining electric potential energy. B) it is moving from low potential to high potential and losing electric potential energy. C) it is moving from high potential to low potential and gaining electric potential energy. D) it is moving from high potential to low potential and losing electric potential energy. E) both its electric potential and electric potential energy remain constant.

C

Two very small plastic balls of equal mass are released from rest. One of them carries +10 µC of excess charge and the other one carries +1µC of charge. No other charges or fields are present. Which of the following statements are true about them as they move away from each other? (There may be more than one correct choice.) A) The acceleration of the 10-µC ball is 10 times that of the 1-µC ball. B) The acceleration of the 1-µC ball is 10 times that of the 10-µC ball. C) The balls always have accelerations of equal magnitude. D) The speed of the balls keeps increasing. E) The acceleration of the balls keeps increasing.

C, D

If two objects are electrically attracted to each other, A) both objects must be negatively charged. B) both objects must be positively charged. C) one object must be negatively charged and the other object must be positively charged. D) the objects could be electrically neutral. E) None of the above statements are absolutely true.

D

Which of the following will increase the capacitance of a parallel-plate capacitor? (There could be more than one correct choice.) A) a decrease in the plate area and an increase in the plate separation B) a decrease in the potential difference between the plates C) an increase in the potential difference between the plates D) an increase in the plate area and a decrease in the plate separation E) an increase in the charge on the plates

D

In outer space, a positive charge q is released near a positive fixed charge Q, as shown in the figure. As q moves away from Q, what is true about the motion of q? (There may be more than one correct choice.) A) It will move with decreasing speed. B) It will move with constant acceleration. C) It will move with increasing acceleration. D) It will move with decreasing acceleration. E) It will move with increasing speed.

D, E

If the electric potential at a point in space is zero, then the electric field at that point must be A) negative. B) zero. C) uniform. D) positive. E) impossible to determine based on the information given.

E