Physics II Final - MisConceptual Questions

What does not affect capacitance?

Charge on the plates Energy stored in the capacitor

Which of the following changes will increase the capacitance of a parallel-plate capacitor?

Decrease the potential between the plates introduce a dielectric material between the plates decrease the separation between the plates

Four identical point charges are arranged at the corners of a square. The electric field E and potential V at the center of the square are

E = 0 but V does not = 0

Q1 = -0.10 mC is located at the origin. Q2 = +0.10 mC is located on the positive x axis at x = 1.0 m. Which of the following is true of the force on Q1 due to Q2?

It is attractive and directed in the + x direction

Q1 = -0.10 mC is located on the positive x axis at x = 1.0 m. Q2 = +0.10 mC is located at the origin. Which of the following is true of the force on Q1 due to Q2?

It is attractive and directed in the - x direction. (Compared to the other problem similar to this: it has changed from the +x direction to the -x direction)

Electrons carry energy from a battery to a lightbulb. What happens to the electrons when they reach the lightbulb?

None of the above Wrong: electrons are emitted as light fewer electrons leave the bulb than enter it electrons are used up electrons stay in the bulb

Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually diminishes on both spheres by leaking off. When each of the spheres has lost half its initial charge, what will be the magnitude of the electrostatic force on each one?

1/4 F

For the graph shown in the figure, what physical quantity does the slope of the graph represent for a dc circuit? (Test 1, Spring 2018)

1/potential

If it takes an amount of work W to move 2 +q point charges from infinity to a distance d apart from each other, then how much work should it take to move 3 +q point charges from infinity to a distance d apart from each other?

3W

The electric potential at a distance of 4 m from a certain point charge is 200 V relative to infinity. What is the potential (relative to infinity) at a distance of 2 m from the same charge?

400 V

Four point charges of equal magnitude 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? (Test 1, Spring 2018)

A - goes southwest

A conductor is placed in a steady external electric field. Which of the following statements are correct for this situation?

The electric field is zero inside the conductor All of the free electrons go to the surface of the conductor The electric field just outside the surface of the conductor is perpendicular to the surface

A + 0.2 mC charge is in an electric field. What happens if that charge is replaced by a +0.4 mC charge?

The electric potential stays the same, but the electric potential energy doubles

The figure below shows electric field lines due to a point charge. What can you say about the field at point 1 compared with the field at point 2? (Ch. 16 #4, p. 468)

The field at point 1 is larger because the field lines are closer together in that region.

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?

The field becomes weaker

A negative point charge is in an electric field created by a positive point charge. Which of the following is true?

The field points away from the positive charge, and the force on the negative charge is in the opposite direction to the field.

A proton (Q = +e) and an electron (Q = -e) are in a constant electric field created by oppositely charged plates. You release the proton from near the positive plate and the electron from near the negative plate. Which feels the larger electric force?

The magnitude of the force is the same for both but in opposite directions

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? (Test 1, Spring 2018)

The potential at points A and B are equal, the potential at point C is lower than the potential at point A

A proton and 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?

Their kinetic energy keeps increasing Their electric potential energy keeps decreasing

Fred the lightening bug has a mass m and a charge +q. Jane, his lightening bug wife, has a mass of 3/4 m and a charge -2q. Because they have charges of opposite sign, they are attracted to each other. Which is attracted more to the other, and by how much?

They are attracted to each other by the same amount.

What affects capacitance?

Area of the plates Separation of the plates Material between the plates

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? (Test 1, Spring 2019)

Trajectory Z --curves downward->

Three equal negative point charges -q 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? (Test 1, Spring 2018)

B - goes southwest

Identical light bulbs can be attached to identical ideal batteries in three different ways (A, B, or C), as shown in the figure. The ranking (from lowest to highest) of the total power produced by the battery is (Test 1, Spring 2018)

B, A, C

When the proton and electron in the above question strike the opposite plate, which one has more kinetic energy?

Both acquire the same kinetic energy

Two small identically charged balls are a certain distance apart. The vectors in the figure show the magnitude and direction of the electrostatic force on each ball due to the other one. Suppose that the charge on the left ball is now doubled (represented by two plus signs). Which vector diagram below best represents the forces that now act on each of the two balls? (Test 1, Spring 2019)

C <---------(++) (+)---------->

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? (Test 1, Spring 2019)

X is negative and Y is positive

If the potential throughout a particular region is constant, the field throughout that region must be zero. Yes or no?

Yes

Is electric field a vector?

Yes

Two equal and opposite charges are a small distance apart, forming an electric dipole. A positive charge +q is placed above these charges, as shown in the figure, equidistant from both of them. Which diagram below best gives the direction of the net force the dipole exerts on the charge +q? (Test 1, Spring 2019)

a right arrow --------> (to the right)

As an object acquires a positive charge, its mass usually

decreases

A battery establishes a voltage V on a parallel plate capacitor. After the battery is disconnected, the distance between the plates is doubled without loss of charge. Accordingly, the capacitance ___ and the voltage between the plates _____

decreases, increases

To be safe during a lightning storm, it is best to be

inside a metal car

As an electron moves in the direction the electric field lines

it is moving from high potential to low potential and gaining electric potential energy

We wish to determine the electric field at a point near a positively charged metal sphere (a good conductor). We do so by bringing a small positive test charge, q0, to this point and measure the force F0 on it. F0/q0 will be ___ the electric field E as it was at that point before the test charge was present

less than

We are usually not aware of the electric force acting between two everyday objects because

most everyday objects have as many plus charges as minus charges

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? (Test 1, Spring 2018)

q1 is negative and q2 is positive the magnitude of q1 is less than the magnitude of q2

Refer to Figure 16-32d, if the two charged plates were moved until they are half the distance shown without changing the charge on the plates, the electric field near the center of the plate would (Ch. 16 #7, p.468)

remain almost exactly the same

Two identical positive charges are placed near each other. At the point halfway between the two charges,

the electric field is zero and the electric potential is positive

A proton is accelerated from rest through a potential difference V and gains a speed v. If it were accelerated instead through a potential difference of 2V, what speed would it gain?

v*(sqrt 2)

Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane, as shown in the figure. These particles are all equidistant from the origin. The electric potential (relative to infinity) at point P on the z-axis due to these particles, is (Test 1, Spring 2019)

zero