Deck 1: Electric Fields

Question 1

A 16-nC charge is distributed uniformly along the x axis from x = 0 to x = 4 m.Which of the following integrals is correct for the magnitude (in N/C) of the electric field at x = +10 m on the x axis?

A)
B)
C)
D)
E)none of these

Answer 1

Question 2

Identical point charges Q are placed at each of the four corners of a 3.0 m *4.0 m rectangle.If Q = 40 $\mu$ C, what is the magnitude of the electrostatic force on any one of the charges?

A)3.0 N
B)2.4 N
C)1.8 N
D)3.7 N
E)2.0 N

Answer 2

2.4 N

Question 3

A point charge Q is placed on the x axis at x = -2.0 m.A second point charge, -Q, is placed at x = 1.0 m.If Q = 60 $\mu$ C, what is the magnitude of the electrostatic force on a 40- $\mu$ C charge placed at the origin?

A)16 N
B)27 N
C)32 N
D)11 N
E)3.0 N

Answer 3

27 N

Question 4

In the figure, if Q = 30 $\mu$ C, q = 5.0 $\mu$ C, and d = 30 cm, what is the magnitude of the electrostatic force on q?

A)15 N
B)23 N
C)zero
D)7.5 N
E)38 N

Question 5

A 12-nC charge is distributed uniformly along the y axis from y = 0 to y = 4 m.Which of the following integrals is correct for the x component of the electric field at x = 2 m on the x axis?

A)
B)
C)
D)
E)none of these

Question 6

A point charge (-5.0 $\mu$ C) is placed on the x axis at x = 4.0 cm, and a second charge (+5.0 $\mu$ C) is placed on the x axis at x = -4.0 cm.What is the magnitude of the electric force on a third charge (+2.5 $\mu$ C) placed on the y axis at y = 3.0 cm?

A)90 N
B)45 N
C)54 N
D)72 N
E)36 N

Question 7

A 24-nC charge is distributed uniformly along the x axis from x = 2 m to x = 6 m.Which of the following integrals is correct for the magnitude (in N/C) of the electric field at x = +8 m on the x axis?

A)
B)
C)
D)
E)none of these

Question 8

A uniform linear charge of 2.0 nC/m is distributed along the x axis from x = 0 to x = 3 m.Which of the following integrals is correct for the x component of the electric field at y = 2 m on the y axis?

A)
B)
C)
D)
E)none of these

Question 9

A charge of 25 nC is uniformly distributed along a circular arc (radius = 2.0 m) that is subtended by a 90-degree angle.What is the magnitude of the electric field at the centre of the circle along which the arc lies?

A)81 N/C
B)61 N/C
C)71 N/C
D)51 N/C
E)25 N/C

Question 10

A 40- $\mu$ C charge is positioned on the x axis at x = 4.0 cm.Where should a -60- $\mu$ C charge be placed to produce a net electric field of zero at the origin?

A)(-5.3 cm)
B)5.7 cm
C)4.9 cm
D)(-6.0 cm)
E)+6.0 cm

Question 11

If a = 60 cm, b = 80 cm, Q = -4.0 nC, and q = 1.5 nC, what is the magnitude of the electric field at point P?

A)68 N/C
B)72 N/C
C)77 N/C
D)82 N/C
E)120 N/C

Question 12

If Q = 25 $\mu$ C, q = 10 $\mu$ C, and L = 40 cm in the figure, what is the magnitude of the electrostatic force on q?

A)28 N
B)22 N
C)20 N
D)14 N
E)10 N

Question 13

If a = 3.0 mm, b = 4.0 mm, Q1 = 60 nC, Q2 = 80 nC, and q = 24 nC in the figure, what is the magnitude of the electric force on q?

A)2.7 N
B)1.9 N
C)2.3 N
D)1.5 N
E)0.52 N

Question 14

A +2.0-nC point charge is placed at one corner of a square (1.5 m on a side), and a -3.0-nC charge is placed on a corner diagonally away from the first charge.What is the magnitude of the electric field at either of the two unoccupied corners?

A)20 N/C
B)14 N/C
C)4.0 N/C
D)12 N/C
E)8.0 N/C

Question 15

A rod (length = 2.0 m) is uniformly charged and has a total charge of 40 nC.What is the magnitude of the electric field at a point which lies along the axis of the rod and is 3.0 m from the centre of the rod?

A)40 N/C
B)45 N/C
C)24 N/C
D)90 N/C
E)36 N/C

Question 16

A uniform linear charge of 2.0 nC/m is distributed along the x axis from x = 0 to x = 3 m.What is the x component of the electric field at y = 2 m on the y axis?

A)(-5.0 N/C)
B)(-4.0 N/C)
C)(-5.7 N/C)
D)(-6.2 N/C)
E)(-9.0 N/C)

Question 17

Charge of uniform density 4.0 nC/m is distributed along the x axis from x =-2.0 m to x = +3.0 m.What is the magnitude of the electric field at the point x = +5.0 m on the x axis?

A)16 N/C
B)13 N/C
C)19 N/C
D)26 N/C
E)5.0 N/C

Question 18

A particle (m = 50 g, q = 5.0 $\mu$ C) is released from rest when it is 50 cm from a second particle (Q = -20 $\mu$ C).Determine the magnitude of the initial acceleration of the 50-g particle.

A)54 m/s2
B)90 m/s2
C)72 m/s2
D)65 m/s2
E)36 m/s2

Question 19

If a = 60 cm, b = 80 cm, Q = -6.0 nC, and q = 3.0 nC in the figure, what is the magnitude of the electric field at point P?

A)71 N/C
B)56 N/C
C)60 N/C
D)53 N/C
E)67 N/C

Question 20

A uniform linear charge density of 7.0 nC/m is distributed along the y axis from y = 2 m to y = 5 m.Which of the following integrals is correct for the magnitude (in N/C) of the electric field at y = 0 on the y axis?

A)
B)
C)
D)
E)none of these

Question 21

A charge of 50- $\mu$ C is placed on the y axis at y = 3.0 cm and a 77- $\mu$ C charge is placed on the x axis at x = 4.0 cm.If both charges are held fixed, what is the magnitude of the initial acceleration of an electron released from rest at the origin?

A)1.2 *1020 m/s2
B)1.5 *1020 m/s2
C)1.0* 1020 m/s2
D)1.8 * 1020 m/s2
E)2.0 *1020 m/s2

Question 22

Two charged particles, Q1 and Q2, are a distance r apart with Q2 = 5Q1.Compare the forces they exert on one another when is the force Q2 exerts on Q1 and is the force Q1 exerts on Q2.

A)= 5.
B)= -5.
C)=
D)= -.
E)5 =

Question 23

A negatively charged particle is moving in the +x-direction when it enters a region with a uniform electric field pointing in the +x-direction.Which graph gives its position as a function of time correctly? (Its initial position is x = 0 at t = 0.)

A)
B)
C)
D)
E)

Question 24

A positively charged particle is moving in the +y-direction when it enters a region with a uniform electric field pointing in the +x-direction.Which of the diagrams below shows its path while it is in the region where the electric field exists.The region with the field is the region between the plates bounding each figure.The field lines always point to the right.The x-direction is to the right; the y-direction is up.

A)
B)
C)
D)
E)

Question 25

A particle (q = 4.0 mC, m = 50 g) has a velocity of 25 m/s in the positive x direction when it first enters a region where the electric field is uniform (60 N/C in the positive y direction).What is the speed of the particle 5.0 s after it enters this region?

A)49 m/s
B)35 m/s
C)32 m/s
D)44 m/s
E)24 m/s

Question 26

Two identical pith balls supported by insulating threads hang side by side and close together, as shown below. One is positively charged; the other is neutral.We can conclude that

A)all field lines leaving the positively charged pith ball end on the neutral pith ball.
B)some of the field lines leaving the positively charged pith ball end on the neutral pith ball.
C)none of the field lines leaving the positively charged pith ball end on the neutral pith ball.
D)positive charge is transferred along the field lines until both balls have equal charges.
E)positive charge is transferred along the field lines until both balls hang along vertical lines.

Question 27

A particle (mass = 4.0 g, charge = 80 mC) moves in a region of space where the electric field is uniform and is given by Ex = -2.5 N/C, Ey = Ez = 0.If the velocity of the particle at t = 0 is given by vx = 80 m/s, vy = vz = 0, what is the speed of the particle at t = 2.0 s?

A)40 m/s
B)20 m/s
C)60 m/s
D)80 m/s
E)180 m/s

Question 28

The symbol appears in Coulomb's law because we use independently defined units for:

A)force and distance.
B)charge and distance.
C)distance and force.
D)force, distance and electric charge.
E)charge.

Question 29

Three pith balls supported by insulating threads hang from a support.We know that ball X is positively charged.When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z.Since pith is an insulating material, we can conclude that:

A)Y has a negative charge.
B)Z has a negative charge.
C)Y has a positive charge.
D)Z has a positive charge.
E)Z is neutral (has no net charge.)

Question 30

When gravitational, magnetic and any forces other than static electric forces are not present, electric field lines in the space surrounding a charge distribution show:

A)the directions of the forces that exist in space at all times.
B)only the directions in which static charges would accelerate when at points on those lines.
C)only the directions in which moving charges would accelerate when at points on those lines.
D)tangents to the directions in which either static or moving charges would accelerate when passing through points on those lines.
E)the paths static or moving charges would take.

Question 31

Two tiny metal spheres are fixed to the ends of a non-conducting string of length .Equal charges, +q, are placed on the metal spheres.Randall says that the force on the string has magnitude .Tilden says that the tension in the string has magnitude .Which one, if either, is correct?

A)Randall, because both charges exert forces on the string, but the tension is
B)Tilden, because both charges exert forces on the string, but the net force is
C)Both are correct, because both charges exert forces on the string.
D)Neither is correct, because both the tension and the force have magnitude
E)Neither is correct, because the tension is , but the net force is 0.

Question 32

When a positive charge q is placed in the field created by two other charges Q1 and Q2, each a distance r away from q, the acceleration of q is:

A)in the direction of the charge Q1 or Q2 of smaller magnitude.
B)in the direction of the charge Q1 or Q2 of greater magnitude.
C)in the direction of the negative charge if Q1 and Q2 are of opposite sign.
D)in the direction of the positive charge if Q1 and Q2 are of opposite sign.
E)in a direction determined by the vector sum of the electric fields of Q1 and Q2.

Question 33

Which one of the diagrams below is not a possible electric field configuration for a region of space which does not contain any charges?

A)
B)
C)
D)
E)

Question 34

Three pith balls supported by insulating threads hang from a support.We know that ball X is positively charged.When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z.Since pith is an insulating material, we can conclude that:

A)Y has a negative charge.
B)Z has a negative charge.
C)Y has a positive charge.
D)Z is neutral (has no net charge.)
E)Y is negatively charged or neutral (has no net charge.)

Question 35

Rubber rods charged by rubbing with cat fur repel each other.Glass rods charged by rubbing with silk repel each other.A rubber rod and a glass rod charged respectively as above attract each other.A possible explanation is that:

A)Any two rubber rods charged this way have opposite charges on them.
B)Any two glass rods charged this way have opposite charges on them.
C)A rubber rod and a glass rod charged this way have opposite charges on them.
D)All rubber rods always have an excess of positive charge on them.
E)All glass rods always have an excess of negative charge on them.

Question 36

A particle (mass = 5.0 g, charge = 40 mC) moves in a region of space where the electric field is uniform and is given by Ex = 2.5 N/C, Ey = Ez = 0.If the velocity of the particle at t = 0 is given by vy = 50 m/s, vx = vz = 0, what is the speed of the particle at t = 2.0 s?

A)81 m/s
B)72 m/s
C)64 m/s
D)89 m/s
E)25 m/s

Question 37

Two imaginary spherical surfaces of radius R and 2R respectively surround a positive point charge Q located at the centre of the concentric spheres.When compared to the number of field lines N1 going through the sphere of radius R, the number of electric field lines N2 going through the sphere of radius 2R is:

A)
B)
C)N2 = N1.
D)N2 = 2N1.
E)N2 = 4N1.

Question 38

A particle (mass = 5.0 g, charge = 40 mC) moves in a region of space where the electric field is uniform and is given by Ex = -5.5 N/C, Ey = Ez = 0.If the position and velocity of the particle at t = 0 are given by x = y = z = 0 and vx = 50 m/s, vy = vz = 0, what is the distance from the origin to the particle at t = 2.0 s?

A)60 m
B)28 m
C)44 m
D)12 m
E)88 m

Question 39

A particle (m = 20 mg, q = -5.0 $\mu$ C) moves in a uniform electric field of 60 N/C in the positive x direction.At t = 0, the particle is moving 25 m/s in the positive x direction and is passing through the origin.How far is the particle from the origin at t = 2.0 s?

A)80 m
B)20 m
C)58 m
D)10 m
E)30 m

Question 40

A particle (m = 20 mg, q = -5.0 $\mu$ C) moves in a uniform electric field of 60 N/C in the positive x direction.At t = 0, the particle is moving 30 m/s in the positive x direction and is passing through the origin.Determine the maximum distance beyond x = 0 the particle travels in the positive x direction.

A)25 m
B)20 m
C)15 m
D)30 m
E)60 m

Question 41

Enrico says that positive charge is created when you rub a glass rod with silk, and that negative charge is simply the absence of positive charge.Rosetta says that negative charge is created and that positive charge is the absence of negative charge.(She has heard that Ben Franklin should have reversed the signs he associated with the charges.) Which one, if either, is correct?

A)Enrico, because there really is only one kind of charge.
B)Rosetta, because there really is only one kind of charge.
C)Neither: although no charge is present originally, both types of charge are created through friction.
D)Both: only one type of charge is created by friction at any one time.
E)Neither: both negative and positive charge are present simultaneously in all solid materials on Earth and the process described involves a transfer of charge, not the creation of charge.

Question 42

A proton moving at 3 * 104 m/s is projected at an angle of 30 $\degree$ above a horizontal plane.If an electric field of 400 N/C is directed downwards, how long does it take the proton to return to the horizontal plane? (HINT: Ignore gravity.) [mProton = 1.67 * 10^-27 kg, qProton = +1.6* 10^-19 C.]

Question 43

Three 2.50 $\mu$ C charges are placed on tiny conducting spheres at the ends of 1.00 m-long strings that are connected at 120 $\degree$ angles as shown below.The magnitude, in N, of the tension in any one of the strings is:

A)1.88 *10^-2.
B)3.25 * 10^-2.
C)3.75 * 10^-2.
D)6.50 * 10^-2.
E)7.50 *10^-2.

Question 44

The electron gun in a television tube accelerates electrons (mass = 9.11 * 10^-31 kg, charge = 1.60*10^-19 C) from rest to 3.00 * 107 m/s within a distance of 2.00 cm.What electric field is required?

Question 45

Imagine for a minute that the Moon is held in its orbit about the Earth by electrical forces rather than by gravitation.What electrical charges -Q on the Earth and +Q on the Moon are necessary to hold the Moon in a circular orbit with a period of 27.3 days? The Earth-Moon distance is 384 000 km and the mass of the Moon is 7.35 * 1022 kg.

Question 46

An alpha particle (charge = +2e) is sent at high speed toward a gold nucleus (charge +79e).What is the electrical force acting on the alpha particle when it is at a distance of 2 *10^-14 m away from the gold nucleus? (e = 1.6 *10^-19 C)