PHYS 216 OCQ 16 Lynch
Three equal charges +Q are at three of the corners of a square of side d. A fourth charge +Q of equal magnitude is at the center of the square as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the center of the square?
B (towards the empty corner)
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.
C (horizontal from positive charge to negative charge)
Four point charges Q of equal magnitude and sign are arranged on three of the corners of the square of side d as shown in the figure Which one of the arrows shown represents the net force acting on the charge at the upper right hand corner of the square?
D (out away from corner)
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?
Only (i) is true.
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.
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.
Which vector best represents the direction of the electric field at the fourth corner of the square due to the three charges shown in Fig. 16-51?
(d)
A small charged plastic ball is vertically above another charged small ball in a frictionless test tube as shown in the figure. The balls are in equilibrium a distance d apart. If the charge on each ball is doubled, the equilibrium distance between the balls in the test tube would become
2d
Four point charges of varying magnitude and sign are arranged on the corners of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the point charge with a charge +Q?
A (out away from corner)
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 (towards empty corner)
Three equal-magnitude point charges of varying signs 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 (towards empty corner)
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 (vertical from + to -)
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?
A (towards middle -Q corner from +Q center)
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 (towards the -Q corner, if 2 +Qs at adjacent corners)
A conductor is placed in a steady external electric field. Which of the following statements are correct for this situation?
All of the above statements are correct. (The electric field is zero inside the conductor, All 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)
Which are unsafe places to be during a lightning storm?
All of the above. (Middle of grassy meadow, on a metal observation tower, next to a tall tree in a forest)
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?
B (towards center of square)
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?
B (towards center of square)
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?
C (towards middle corner)
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?
C (equal length, longest arrows)
Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude F0 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?
F0/4
Electrically neutral objects cannot exert an electrical force on each other, but they can exert a gravitational force on each other.
False
Swap the positions of Q1 and Q2 of MisConceptual Question 1. Which of the following is true of the force on Q1 due to Q2?
It changes from the +x direction to the -x direction.
Q1 = - 0.10 µC is located at the origin. Q2 = +0.10 µC 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.
Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are doubled and their separation is also doubled, what happens to the electrical force that each charge exerts on the other one?
It remains the same.
Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are halved and their separation is also halved, what happens to the electrical force that each charge exerts on the other one?
It remains the same.
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?
It will move with increasing speed.
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 +1 µC 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?
The balls have accelerations of equal magnitude.
Fig. 16-50 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?
The field at point 1 is larger, because the field lines are closer together in that region.
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.
Two tiny beads are 25 cm apart with no other charges or fields present. Bead A carries 10 µC of charge and bead B carries 1 µC. Which one of the following statements is true about the magnitudes of the electric forces on these beads?
The force on A is exactly equal to the force on B.
A plastic rod and a glass rod are charged by rubbing with a piece of fur.
The plastic rod will be charged negatively
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?
The top surface is charged positively.
Fred the lightning bug has a mass m and a charge +q. Jane, his lightning-bug wife, has a mass of ¾m 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.
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?
They are closer to the to the initial position of the proton that to the initial position of the electron.
The figure shows two unequal charges, +q and -Q. Charge -Q has greater magnitude than charge +q. Point X is midway between the charges. Within which section of the line will there be a point where the resultant electric field is zero?
VW
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?
X is negative and Y is positive.
As an object acquires a positive charge, its mass usually
decreases
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 charge to 2Q.
To be safe during a lightning storm, it is best to be
inside a metal car.
A plastic rod is charged up by rubbing a wool cloth, and brought to an initially neutral metallic sphere that is insulated from ground. It is allowed to touch the sphere for a few seconds, and then is separated from the sphere by a small distance. After the rod is separated, the rod
is repelled by the sphere.
We wish to determine the electric field E 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 measuring 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
A small metal ball hangs from the ceiling by an insulating thread. The ball is attracted to a positively charged rod held near the ball. The charge of the ball must be
negative or neutral.
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
positively charged.
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?
q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2.
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
sphere 1 carries positive charge and 2 carries negative charge.
If two objects are electrically attracted to each other,
the objects could be electrically neutral.
A hydrogen nucleus, which has a charge +e, is situated to the left of a carbon nucleus, which has a charge +6e. The electrical force experienced by the hydrogen nucleus is
to the left, and the magnitude is equal to the force exerted on the carbon nucleus.
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 Z (curving downwards)
Four tiny charged particles (two having a charge +Q and two having a charge -Q) are distributed on the x- and y-axes as shown in the figure. Each charge is equidistant from the origin. In which direction is the net electric field at the point P on the y-axis?
upwards and a little towards the left
