Physics Exam I

11. Charged glass and plastic rods hang by threads. An object attracts the glass rod. If this object is then held near the plastic rod, it will a.Attract the plastic rod. b.Repel the plastic rod. c.Not affect the plastic rod. d.Either A or B. There's not enough information to tell.

D

An electron is initially moving to the right when it enters a uniform electric field directed upwards, as shown in the figure. Which trajectory (X, Y, Z, or W) will the electron follow in the field? A) trajectory W B) trajectory X C) trajectory Y D) trajectory Z

D

In outer space, a positive charge q is released near a bigger positive fixed charge Q, as shown in the figure. As q moves away from Q due to repulsion, what is true about the motion of q? (As perNewton's second law of motion Force is equal to the mass times acceleration). 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.

D

The electric potential at a certain point is space is 12 V. What is the electric potential energy of a -3.0 μC charge placed at that point? (a) +4 μJ (c) +36 μJ (e) zero µJ (b) -4 μJ (d) -36 μJ

D

The magnitude of electric force was measured to be 400 N, due North on a -2 C of charge. What is the magnitude and direction of the electric field at that point? A) 2 × 102 N/C , due North B) 4 × 102 N/C , due North C) 4 × 108 N/C , due West D) 2 × 102 N/C , due South, E) None of the above

D

Two stationary point charges q1 and q2 are shown in the figure along with a sketch of some field lines representing the electric field produced by them. What can you deduce from the sketch? A) q1 is negative and q2 is positive; the magnitudes are equal. B) q1 and q2 have the same sign; the magnitudes are equal. C) q1 is positive and q2 is negative; the magnitude of q1 is greater than the magnitude of q2. D) q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2. E) q1 and q2 have the same sign; the magnitude of q1 is greater than the magnitude of q2.

D

Which one of the following statements best describes the equipotential surfaces surrounding a point charge? (a) The equipotential surfaces are planes extending radially outward from the charge. (b) The equipotential surfaces are curved planes surrounding the charge, but only one passes through the charge. (c) The equipotential surfaces are concentric cubes with the charge at the center. (d) The equipotential surfaces are concentric spheres with the charge at the center. (e) The equipotential surfaces are concentric cylinders with the charge on the axis at the center.

D

Which one of the following statements is true concerning the electrostatic charge on a conductor? (A) The charge is uniformly distributed throughout the volume. (B) The charge is confined to the surface and is uniformly distributed. (C) Most of the charge is on the outer surface, but it is not uniformly distributed. (D) The charge is entirely on the surface and it is distributed according to the shape of the object. (E) The charge is dispersed throughout the volume of the object and distributed according to the object's shape.

D

Which one of the following statements is true concerning the electrostatic charge on a conductor? (a) The charge is uniformly distributed throughout the volume. (b) The charge is confined to the surface and is uniformly distributed. (c) Most of the charge is on the outer surface, but it is not uniformly distributed. (d) The charge is entirely on the surface and it is distributed according to the shape of the object. (e) The charge is dispersed throughout the volume of the object and distributed according to the object's shape.

D

X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y is now moved away from X, as shown in part (b). What are the final charge states of X and Y? A) Both X and Y are neutral. B) X is positive and Y is neutral. C) X is neutral and Y is positive. D) X is negative and Y is positive. E) Both X and Y are negative.

D

13. Metal spheres 1 and 2 are touching. Both are initially neutral. The charged rod is brought near. The charged rod is then removed. The spheres are separated. Afterward, the charges on the sphere are: a.Q1 is + and Q2 is + b.Q1 is + and Q2 is - c.Q1 is - and Q2 is + d.Q1 is - and Q2 is - e.Q1 is 0 and Q2 is 0

E

A parallel plate capacitor with plates of area A and plate separation d is charged so that the potential difference between its plates is V. What happens to its capacitance if the potential difference between the plates is reduced by 1⁄2V ? A) The capacitance is twice its original value.B) The capacitance is four times its original value. C) The capacitance is eight times its original value. D) The capacitance is one half of its original value. E) The capacitance is unchanged.

E

A rod attracts a positively charged hanging ball. The rod is... a.Positive. b.Negative. c.Neutral. d.Either A or C. e.Either B or C.

E

If the work required to move a +0.35 C charge from point A to point B is +125 J, what is the potential difference between the two points? (a) zero volts (c) 88 V (e) 360 V (b) 44 V (d) 180 V

E

Two positive point charges Q and 2Q are separated by a distance d . If the charge Q experiences a force of magnitude F when the separation is d, what is the magnitude of the force on the charge 2Q when the separation is decreased to d/4 ? A) F/16 B) F/4 C) F D) 4F E) 16F

E

Which one of the following statements is true concerning the magnitude of the electric field at a point in space? (a) It is a measure of the total charge on the object. (b) It is a measure of the electric force on any charged object. (c) It is a measure of the ratio of the charge on an object to its mass. (d) It is a measure of the electric force per unit mass on a test charge. (e) It is a measure of the electric force per unit charge on a test charge.

E

A charge Q exerts a 12 N force on another charge q. If the distance between the charges is doubled, what is the magnitude of the force exerted on Q by q? (a) 3 N (c) 24 N (e) 48 N (b) 6 N (d) 36 N

A

Complete the following statement: The electromotive force is A) the maximum potential difference between the terminals of a battery. B) the force that accelerates electrons through a wire when a battery is connected to it. C) the force that accelerates protons through a wire when a battery is connected to it. D) the maximum capacitance between the terminals of a battery. E) the maximum electric potential energy stored within a battery.

A

Complete the following statement: The electron volt is a unit of (a) energy. (c) electric charge. (e) electric power. (b) electric field strength. (d) electric potential difference.

A

Four point charges of equal magnitudes but with varying signs are arranged on three of the corners and at the center of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the center charge? A) A, B) B, C) C, D) D E) None of these

A

If a charge generator builds a negative static charge of - how many electrons are transferred to it during this process? (e = 1.60 × 10^-19 C) A) 4.38 × 1013 B) 7.0 C) 1.12 × 10-18 D) 43.8

A

The figure shows electric field lines arising from two small charged particles P and Q. Consider the following two statements: (i) The charge on P is smaller than the charge on Q.(ii) The electrostatic force on P is smaller than the force on Q. Which of the above statements are true? A) Only (i) is true.B) Only (ii) is true.C) Both (i) and (ii) are true. D) Neither (i) nor (ii) is true.

A

Which one of the arrows shown in the figure best represents the direction of the electric field between the two uniformly charged metal plates? A) A B) B C) C D) D E) None of the above

A

Coulomb's law describes a.The electric field due to a point charge. b.The force between two point charges. c.The electric field due to a charged rod. d.The electric potential of a point charge.

B

The field inside a charged parallel-plate capacitor is a.Zero. b.Uniform. c.Parallel to the plates. d.Directed from the negative to the positive plate.

B

The sketch below shows cross sections of equipotential surfaces between two charged conductors that are shown in solid grey. Various points on the equipotential surfaces near the conductors are labeled A, B, C, ..., I. At which of the labeled points will the electric field have the greatest magnitude? (a) G (c) A (e) D (b) I (d) H

B

Two charges Q1(100 C) and Q2(2C) are separated at a distance of r =2m. The electric field experience by the charge Q2 due to the presence of charge Q1 will be A) proportional to the magnitude of Charge Q2 = 2C B) proportional to the magnitude of Charge Q1=100 C C) inversely proportional to the distance = 2m D) proportional to the product of Q1 and Q2 E) All of the above.

B

10. The electric field inside a metallic conductor is a.Positive. b.Negative. c.Zero.

C

14. Metal spheres 1 and 2 are touching. Both are initially neutral. The charged rod is brought near. The spheres are separated. The charged rod is then removed. a.Q1 is + and Q2 is + b.Q1 is + and Q2 is - c.Q1 is - and Q2 is + d.Q1 is - and Q2 is - e.Q1 is 0 and Q2 is 0

C

A conducting sphere has a net charge of −4.8 ◊ 10−17 C. What is the approximate number of excess electrons on the sphere? (a) 100 (c) 300 (e) 500 (b) 200 (d) 400

C

Five styrofoam balls are suspended from insulating threads. Several experiments are performed on the balls; and the following observations are made: I. Ball A attracts B and A repels C. II. Ball D attracts B and D has no effect on E. III. A negatively charged rod attracts both A and E. What are the charges, if any, on each ball? A B C D E (a) + - + 0 + (b) + - + + 0 (c) + - + 0 0 (d) - + - 0 0 (e) + 0 - + 0

C

The magnitude of the charge on the plates of an isolated parallel plate capacitor is doubled. Which one of the following statements is true concerning the capacitance of this parallel-plate system? (a) The capacitance is decreased to one half of its original value. (b) The capacitance is increased to twice its original value. (c) The capacitance remains unchanged. (d) The capacitance depends on the electric field between the plates. (e) The capacitance depends on the potential difference across the plates.

C

Two point charges are separated by 1.00 ◊ 10−2 m. One charge is −2.8 ◊ 10−8 C; and the other is +2.8 ◊ 10−8 C. The points A and B are located 2.5 ◊ 10−3 m from the lower and upper point charges as shown. 4. If an electron, which has a charge of 1.60 × 10−19 C, is moved from rest at A to rest at B, what is the change in electric potential energy of the electron? (a) +4.3 ◊ 10−15 J (c) -2.1 ◊ 10−14 J (e) zero joules (b) +5.4 ◊ 10−15 J (d) -3.2 ◊ 10−14 J

C

Which one of the following changes will necessarily increase the capacitance of a capacitor? (a) decreasing the charge on the plates (b) increasing the charge on the plates (c) placing a dielectric between the plates (d) increasing the potential difference between the plates (e) decreasing the potential difference between the plates

C

Which one of the following figures shows a qualitatively accurate sketch of the electric field lines in and around this system?

c

Which one of the following statements best explains why tiny bits of paper are attracted to a charged rubber rod? (a) Paper is naturally a positive material. (d) Rubber and paper always attract each other. (b) Paper is naturally a negative material. (e) The paper acquires a net positive charge by induction (c) The paper becomes polarized by induction. induction.

c