Physics Chapter 20

A small styrofoam ball of mass 0.120 g is placed in an electric field of 6000 N/C pointing downward. What excess charge must be placed on the ball for it to remain suspended in the field? -16.0 nC -18.0 nC -57.2 nC -125 nC -196 nC

-196 nC

Four point charges of magnitude 6.00 μC and are at the corners of a square 2.00 m on each side. Two of the charges are positive, and two are negative. What is the electric potential at the center of this square, relative to infinity, due to these charges? (k = 1/4πε0 = 8.99 × 109 N •m2/C2) 76.4 kV 0 V 153 kV 61.0 kV 306 kV

0 V

How much work is needed to carry an electron from the positive terminal to the negative terminal of a 9.0-V battery. (e = 1.60 × 10-19 C , melectron = 9.11 × 10-31 kg) 1.6 × 10-19 J 17 × 10-19 J 9.0 J 14.4 × 10-19 J 14.4 × 10-19 J/C

14.4 × 10-19 J

A small object with a 5.0-μC charge is accelerating horizontally on a friction-free surface at 0.0050 m/s2 due only to an electric field. If the object has a mass of 2.0 g, what is the magnitude of the electric field? 2.0 N/C 4.0 N/C 0.0020 N/C 0.0040 N/C 1.0 N/C

2.0 N/C

What charge accumulates on the plates of a 2.0-μF air-filled capacitor when it is charged until the potential difference across its plates is 100 V? 50 μC 100 μC 150 μC 200μC

200μC

An air-filled capacitor has a potential difference between the plates of 80 V. If the charge on each of the plates of the capacitor has magnitude 8.0 μC, what is the electrical energy stored by this capacitor? 640 µJ 320 µJ 50 nJ 60 nJ 30 pJ

320 µJ

The electric potential at a distance of 4 m from a certain point charge is 200 V relative to infinity. What is the potential at a distance of 2 m from the same charge? 200 V 50 V 400 V 100 V 600 V

400 V

When the magnitude of the charge on each plate of an air-filled capacitor is 4 μC, the potential difference between the plates is 80 V. What is the capacitance of this capacitor? 0.1 µF 50 µF 100 µF 20 µF 50 nF

50 nF

A battery maintains the electrical potential difference of 6.0-V between two large parallel metal plates separated by 1.0 mm. What is the strength of the electric field between the plates? 6.0 V/m 600 V/m 6000 V/m zero

6000 V/m

Three equal positive point charges +q are placed at 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 center of the square? A B C D

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 B C D None of the above

A

Charges with opposite charges do what Repel Attract Go in circles Nothing

Attract

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? A B C D

B

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 center of the square? A B C D

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? The potential at all three locations is the same. The potentials at points A and B are equal, and the potential at point C is higher than the potential at point A. The potential at points A and B are equal, and the potential at point C is lower than the potential at point A. 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.

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

A negatively-charged rod is brought close to (but does not touch) two neutral spheres that are in contact with each other but insulated from the ground. If the two spheres are then separated, what kind of charge will be on the spheres? The sphere near the charged rod becomes positive and the other one becomes negative. The sphere near the charged rod becomes negative and the other one becomes positive. The spheres do not get any charge. Both spheres become negative. Both spheres become positive.

The sphere near the charged rod becomes positive and the other one becomes negative.

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? Both X and Y are neutral. X is positive and Y is neutral. X is neutral and Y is positive. X is negative and Y is positive. Both X and Y are negative.

X is negative and Y is positive.

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 double the distance to 2R. double the charge to 2Q. reduce the distance to R/2. reduce the distance to R/4. double the charge to 2Q and at the same time reduce the distance to R/2.

double the charge to 2Q.

True or False: Like charges will attract. true false

false

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 increases. decreases. remains the same. depends on the zero point of the potential.

increases.

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

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

As a proton moves in the direction the electric field lines it is moving from low potential to high potential and gaining electric potential energy. it is moving from low potential to high potential and losing electric potential energy. it is moving from high potential to low potential and gaining electric potential energy. it is moving from high potential to low potential and losing electric potential energy. both its electric potential and electric potential energy remain constant.

it is moving from high potential to low potential and losing electric potential energy.

A negatively-charged plastic rod is brought close to (but does not touch) a neutral metal sphere that is connected to ground. After waiting a few seconds, the ground connection is removed (without touching the sphere), and after that the rod is also removed. The sphere is now negatively charged. positively charged. neutral.

positively charged.

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 spheres #1 and #2 are still uncharged. sphere #1 carries positive charge and #2 carries negative charge. sphere #1 carries negative charge and #2 carries positive charge. spheres #1 and #2 both carry positive charge. spheres #1 and #2 both carry negative charge.

sphere #1 carries positive charge and #2 carries negative charge.

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? trajectory W trajectory X trajectory Y trajectory Z

trajectory Z

True or False: Electric field lines will flow from positive charge to negative charge true false

true