Physic 2 test 1 concepts (Ch.1-19)
Which of the following combination of units are those for the strength of the electric field?
N/C
Which one of the following statements concerning equipotential surfaces is false?
No work is done by the net electric force as a charge moves from one equipotential surface to another.
Which of the following statements describes an object being charged by induction?
A positively-charged object is brought near with an initially uncharged insulator. The surface of the insulator becomes slightly negatively charged
A Gaussian surface contains a single charge within it, and as a result an electric flux passes through the surface. Suppose that the charge is then moved to another spot within the Gaussian surface. Does the flux through the surface change?
No, because the charge is still within the Gaussian surface.
Two different charges, q1 and q2, are placed at two different locations, one charge at each location. The locations have the same electric potential V. Do the charges have the same electric potential energy?
No, because the electric potential energy EPE at a given location depends on the charge placed at that location as well as the electric potential V.
A particle is attached to one end of a horizontal spring, and the other end of the spring is attached to a wall. When the particle is pushed so that the spring is compressed more and more, the particle experiences a greater and greater force from the spring. Similarly, a charged particle experiences a greater and greater force when pushed closer and closer to another particle that is fixed in position and has a charge of the same polarity. Considering this similarity, will the charged particle exhibit simple harmonic motion on being released, as will the particle on the spring?
No, because the force on the charged particle will always be in the same direction.
In a region of space where the electric field is constant everywhere, as it is inside a parallel plate capacitor, is the potential constant everywhere?
No, the potential is greatest at the positive plate.
Which of the following changes would result in an increase in the energy stored in a parallel-plate capacitor, assuming all other variables remain constant?
None of the changes listed above will change the energy stored in the capacitor.
Consider a spot that is located midway between two identical point charges. Which one of the following statements concerning the electric field and the electric potential at this spot is true?
The electric field is zero, but the electric potential is not zero
Which one of the following statements is true concerning scalar quantities?
Scalar quantities can be added to other scalar quantities using rules of ordinary addition
Which one of the following statements is true concerning scalar quantities?
Scalar quantities can be added to other scalar quantities using rules of ordinary addition.
Point charge A is located at point A and point charge B is at point B. Points A and B are separated by a distance r. To determine the electric potential at the mid-point along a line between points A and B, which of the following mathematical approaches is correct?
The algebraic sum of the two electric potentials is determined at a distance r/2 from each of the charges, making sure to include the signs of the charges.
A parallel plate capacitor is connected to a battery that maintains a constant potential difference between the plates. If the plates are pulled away from each other, increasing their separation, what happens to the amount of charge on the plates?
The amount of the charge decreases, because the capacitance decreases.
The length and width of each plate of a parallel plate capacitor are doubled, and the spacing between the plates is also doubled. By what factor does the capacitance change?
The capacitance increases by a factor of 2.
What happens to a capacitor when an insulator is inserted between the two conductors of the capacitor?
The capacitance of the capacitor increases.
An isolated system consists of two conducting spheres A and B. Sphere A has five times the radius of sphere B. Initially, the spheres are given equal amounts of positive charge and are isolated from each other. The two spheres are then connected by a conducting wire.Note: The potential of a sphere of radius R that carries a charge Q is V = kQ/R, if the potential at infinity is zero. Which one of the following statements is true after the spheres are connected by the wire?
The electric potential of A equals that of B.
An electrically neutral object acquires a net electric charge. Which one of the following statements concerning the mass of the object is true?
The mass increases if the charge is negative and decreases if it is positive.
Which one of the following statements concerning the net electric charge on an object is true?
The net charge is quantized.
Which one of the following statements concerning equipotential surfaces is true?
The net work done by electric forces that move a charge along an equipotential surface is equal to zero joules.
When the distance between charged parallel plates of a capacitor is d, the potential difference is V. If the distance is decreased to d/2, how will the potential difference change, if at all?
The new potential difference would be twice the previous value.
Points A, B, and C lie along a line from left to right, respectively. Point B is at a lower electric potential than point A. Point C is at a lower electric potential than point B. Which one of the following statements best describes the subsequent motion, if any, of a positively-charged particle released from rest at point B?
The particle will accelerate in the direction of point C.
A positively charged ebonite rod is brought close to a small ball. The rod does not touch the ball, which is made from a conducting material. The ball is electrically neutral. Which one of the following statements is true?
The rod attracts the ball.
Which one of the following rules, laws, or principles describes how the net electric charge of an isolated system undergoing any process remains constant?
law of conservation of electric charge
Two metal spheres are identical. They are electrically neutral and are touching. An electrically charged ebonite rod is then brought near the spheres without touching them, as the drawing shows. After a while, with the rod held in place, the spheres are separated, and the rod is then removed. The following statements refer to the masses mA and mB of the spheres after they are separated and the rod is removed. Which one or more of the statements is true?
-mA < mB if the rod is negative -mA > mB if the rod is positive
Two vectors A and B are added together to form a vector . The relationship between the magnitudes of the vectors is given by A + B = C. Which one of the following statements concerning these vectors is true?
A and B must point in the same direction
Three point charges are fixed to the corners of a square, one to a corner, in such a way that the net electric field at the empty corner is zero. Do these charges all have (a) the same sign and (b) the same magnitude (but, possibly, different signs)?
(a) No. (b) No.
An ion, starting from rest, accelerates from point A to point B due to a potential difference between the two points. Does the electric potential energy of the ion at point B depend on (a) the magnitude of its charge and (b) its mass? Does the speed of the ion at B depend on (c) the magnitude of its charge and (d) its mass?
(a) Yes. (b) No. (c) Yes. (d) Yes
An electric potential energy exists when two protons are separated by a certain distance. Does the electric potential energy increase, decrease, or remain the same (a) when both protons are replaced by electrons, and (b) when only one of the protons is replaced by an electron?
(a) remain the same, (b) decrease
Object A and object B are each electrically neutral. Two million electrons are removed from object A and placed on object B. Expressed in coulombs, what is the resulting charge (algebraic sign and magnitude) on object A and on object B?
+3.2 x 10^-13 C on A, -3.2 x 10^-13 C on B
The electric potential at a certain point in space is 12 V. What is the electric potential energy of a -3.0 μC charge placed at that point?
-36 μJ
Which one of the following choices is a vector quantity
-displacement -the earths pull on your body
Which two, or more, of the following actions would increase the energy stored in a parallel plate capacitor when a constant potential difference is applied across the plates?
-increase the area of the plates -decrease the separation between the plates -insert a dielectric between the plates
Which one of the following values is the smallest possible amount of free charge that has been discovered?
1.60 × 10-19 coulombs
What is the angle between the vectors and - when they are drawn from a common origin?
180°
A completely ionized beryllium atom (net charge = +4e) is accelerated through a potential difference of 6.0 V. What is the increase in kinetic energy of the atom?
24 eV
Which one of the following statements concerning vectors and scalars is false?
A vector that is zero may have components other than zero.
Consider the following four possibilities for two point charges and choose the one(s) that do not change the magnitude of the electrostatic force that each charge exerts on the other:
A. Double the magnitude of each charge and double the separation between them. D. Double the magnitude of only one charge and increase the separation between the charges by a factor of .
Which of the following statements concerning electric field lines is false?
An electric field line indicates the direction of the force on an electron placed on the line.
A positively-charged particle is held at point A between two parallel metal plates. The plate on the left has a net positive charge +q and the plate on the right has a net negative charge -q. The particle is then moved to point B which is far from other charges. How does the electric potential energy at point A compare with that at point B?
EPEA > EPEB
Which one of the following statements concerning parallel plate capacitors is false?
Electric field lines are directed from the negative plate to the positive plate.
Which one of the following statements concerning atoms is false?
Electrical charges are uniformly distributed throughout the volume occupied by an atom.
Consider two identical, thin, and nonconducting rods, A and B. On rod A, positive charge is spread evenly, so that there is the same amount of charge per unit length at every point. On rod B, positive charge is spread evenly over only the left half, and the same amount of negative charge is spread evenly over the right half. What is the direction of the electric field at a point that is located directly above the midpoint of each rod?
For A, the direction is up. For B, the direction is to the right.
Because of an electric field, a positive charge +q experiences a force of magnitude F that points due west. The positive charge is then replaced with a negative charge -2q. What force does the negative charge experience?
Force magnitude = 2F, force direction is due east
Each of two identical objects carries a net charge. The objects are made from conducting material. One of them is attracted to a positively charged ebonite rod, and the other is repelled by the rod. After the objects are touched together, it is found that they are each repelled by the rod. What can be concluded about the initial charges on the objects?
Initially one object is positive and one is negative, with the positive charge having a greater magnitude than the negative charge.
A physics student adds two displacement vectors with magnitudes of 8.0 km and 6.0 km. Which one of the following statements is true concerning the magnitude of the resultant displacement?
It could have any value between 2.0 km and 14.0 km depending on how the vectors are oriented.
Which one of the following statements concerning the electric force is true?
It is possible for a small negatively-charged particle to float above a negatively charged surface.
A conductor that is initially electrically neutral is touched by a rod that has a net positive charge. Which of the following statements describing the conductor after the rod is removed is true?
The conductor will have a net positive charge.
Which one of the following statements is a consequence of charge being conserved?
The difference between the number of positive and negative charges does not change for a given closed system.
An electron is a negatively charged particle that has a charge of magnitude, e = 1.60 × 10-19 C. Which one of the following statements best describes the electric field at a distance r from the electron?
The electric field is directed toward the electron and has a magnitude of ke/r2.
The electric potential V is constant everywhere within a certain region of space. Which statement below is true?
The electric field is zero everywhere within the region.
Which one of the following statements best describes the equipotential surfaces surrounding a point charge?
The equipotential surfaces are concentric spheres with the charge at the center.
A rod made from insulating material carries a net charge (which may be positive or negative), whereas a copper sphere is electrically neutral. The rod is held close to the sphere but does not touch it. Which one of the following statements concerning the forces that the rod and sphere exert on each other is true?
The forces are always attractive.
A vector is represented by an arrow. What is the significance of the length of the arrow?
The length of the arrow is proportional to the magnitude of the vector.
Two positively charged particles are separated by a distance r. The force on particle 1 is F due to particle 2. The force on particle 2 is 2F due to particle 1. Is the previous sentence true or false? Explain why this is the case.
The sentence is false because the forces on each of the two objects are equal in magnitude, as well as opposite in direction.
A battery charges capacitor A until the potential difference between the two conductors of the capacitor is V. A second, identical capacitor, labeled B, is charged by another battery until the potential difference of capacitor B is 2V. How does the stored energy of capacitor B compare to that of capacitor A?
The stored energy of capacitor B is four times that of capacitor A.
Consider the two charged particles situated as follows: One charge located on the y axis has a value -2q and is located at a distance r from the origin, point O. The other charge has a value -q and is located at a distance 2r from the origin along the x axis. Which one of the following statements concerning the electric potential at the origin is true?
The total electric potential at the origin is equal to -5kq/2r.
There is an electric field at point P. A very small positive charge is placed at this point and experiences a force. Then the positive charge is replaced by a very small negative charge that has a magnitude different from that of the positive charge. Which one of the following statements is true concerning the forces that these charges experience at P?
They have different magnitudes and different directions.
Each of three objects carries a charge. As the drawing shows, objects A and B attract each other, and objects C and A also attract each other. Which one of the following statements concerning objects B and C is true?
They repel each other.
A positive point charge is located to the left of a negative point charge. When both charges have the same magnitude, there is no place on the line passing through both charges where the net electric field due to the two charges is zero. Suppose, however, that the negative charge has a greater magnitude than the positive charge. On which part of the line, if any, is a place of zero net electric field now located?
To the left of the positive charge
You have two identical metal spheres and a negatively charged ebonite rod. Without touching the rod to the spheres, which one of the following procedures can you use to give each sphere a net electrical charge of the same magnitude, one being positive and the other being negative.
Touch the two spheres together. Bring the rod near one sphere, opposite the place where the spheres are touching. Then, with the rod in place, separate the spheres
Imagine that you are moving a positive test charge alone the line between two identical point charges. With regard to the electric potential, is the midpoint on the line analogous to the top of a mountain or the bottom of a valley when the two point charges are (a) positive and (b) negative?
a) bottom of a valley (b) top of a mountain
Complete the following sentence: an electric insulator has
few electrons available to conduct electricity.
The direction of the electric field is the same as which of the following properties related to a test charge?
force on a positive test charge
A parallel plate capacitor is charged up by a battery. The battery is then disconnected, but the charge remains on the plates. The plates are then pulled apart. Does the energy stored by the capacitor increase, decrease or remain the same as the distance between the plates increases?
increase
An empty parallel plate capacitor is connected to a battery that maintains a constant potential difference between the plates. With the battery connected, a dielectric is then inserted between the plates. Does the energy stored by the capacitor increase, decrease or remain the same when the dielectric is inserted?
increase
Which of the following terms is used to describe a material that does not allow electrons to easily move through it?
insulator
A certain physical quantity, R, is calculated using the formula: R = 4a2(b - c) where a, b, and c are distances. What is the SI unit for R?
m3
A positive test charge is placed in an electric field. In what direction should the charge be moved relative to the field, so that the charge experiences a constant electric potential? The charge should be moved
perpendicular to the electric field.
Which one of the following changes will necessarily increase the capacitance of a capacitor?
placing a dielectric between the plates
A conducting sphere is connected via a wire to the ground. For a very short time, electrons move from the ground to the sphere. Then, no more electrons move to the sphere. Complete the following sentence: Before the wire was connected, the sphere's electric potential had a
positive value.
A positive point charge q1 creates an electric field of magnitude E1 at a spot located at a distance r1 from the charge. The charge is replaced by another positive point charge q2, which creates a field of magnitude E2 = E1 at a distance of r2 = 2r1. How is q2 related to q1?
q2 = 4q1
Only one of three balls A, B, and C carries a net charge q. The balls are made from conducting material and are identical. One of the uncharged balls can become charged by touching it to the charged ball and then separating the two. This process of touching one ball to another and then separating the two balls can be repeated over and over again, with the result that the three balls can take on a variety of charges. Which one of the following distribution of charges could not possibly be achieved in this fashion, even if the process were repeated an infinite number of times?
qA=1/2q, qB=3/8q, qC=1/4q
Complete the following statement: When a dielectric with constant κ is inserted between the plates of a charged isolated capacitor
the electric field between the plates is reduced by a factor of κ.
A proton and an electron are held in place on the x axis. The proton is at x = -d, while the electron is at x = +d. They are released simultaneously, and the only force that affects their motions significantly is the electrostatic force of attraction that each applies to the other. Which particle reaches the origin first?
the electron
A proton and an electron are released from rest at the midpoint between the plates of a charged parallel plate capacitor. Except for these particles, nothing else is between the plates. Ignore the attraction between the proton and the electron, and decide which particle strikes a capacitor plate first.
the electron
A proton is fixed in place. An electron is released from rest and allowed to collide with the proton. Then the roles of the proton and electron are reversed, and the same experiment is repeated. Which, if either, is traveling faster when the collision occurs, the proton or the electron?
the electron
