Reading Quiz

Question 1:

Answer:

1. Lots of things. Gauss' law is amazing. It lets us look at flux without knowing the field strength and then use the other side of the equation to find the field strength. Also, really important: it lets us do those nasty integrals from chapter 20 really easily. And it applies to all electric fields, not just point charges (which really aren't all that common in the real world after all.)
2. Gauss's Law can be used for the calculation of the electric flux through surfaces of various types of objects. It can also be used to shorten solutions of problems involving electric fields from the priorly used derivation of Coulomb's Law.
3. Gauss' Law can be used to found electric flux, charge enclosed and the electric field.
4. To derive an expression for electric fields of high-symmetry structures.
5. To compute the strength of an electric field on a conductor surface, to determine the flux through a gaussian surface and the electric field within and outside a closed surface
6. Gauss' Law can be used for finding the electric field from charge distributions by using surface areas that enclose the charge and the enclosed charge itself. It can also be a more convenient way to find the flux through some closed surface with an enclosed charge.
7. Gauss' Law can be used to find out the flux of a given object experiencing an electric field, as well as the electric field that is at the surface of a conductor.
8. Gauss' law can be used to calculate electric field at a point near a charged body.
9. Gauss' law can be used to make the electric field calculation easier.
10. Finding the electric field for a charge symmetric about a point a line or a plane
11. Gauss' law can be used to calculate the electric flux or the electric field of any charge, provided it is enclosed by a Gaussian surface
12. Gauss's Law can be used to find the strength of an electric field when it is difficult to calculate the field strength directly.
13. We use Gauss' Law to prove that excess charge must be at the surface of a conductor in electric equilibrium
14. Gauss' law can be used for finding the electric field and flux in a charged area.
15. Gauss' law can be used to find the flux through a closed surface.
16. Gauss' law is used to calculate the electric flux through any closed surface.

Question 2:

Answer:

1. I feel like this question is a little misleading, but I might just be confused. I think it depends on the shape of the conductor and the situation. If you just have a rectangular sheet of conductor cutting across an external electric field, then the positive and negative charges are going to zoom to opposite ends of the conductor, creating their own field in the opposite direction of the external field. They won't stop until the field they create is equal and opposite to the external field (aka reach equilibrium). This would mean (i think) that the field very close to this conductor would be zero. However, in the case of a hollow spherical conductor with a charge in the center, at a point near to the surface of the sphere, the field will simply be (kq/r^2)r hat. (This is why I think I might be confused. Shouldn't there be a general answer for a general case?
2. The orientation of the electric field just outside the surface of a conductor is a straight line, I suppose. Since its just outside the surface of the conductor, the field has not yet changed orientation in response to any external charges or fields.
3. The electric field is perpendicular to the surface of a conductor.
4. It is perpendicular
5. perpendicular to the surface of the conductor
6. The electric field is oriented exactly perpendicular to the surface of a conductor with direction depending on the charge.
7. At a conductor's surface, the electric field is equal to the surface charge density devided by epsilon not.
8. The field at the surface of a conductor is perpendicular to the surface.
9. Perpendicular to its tangent.
10. It depends on the direction of the electric field and whether the conductor has a charge.
11. The electric field is perpendicular to the surface of the conductor just outside the conductor.
12. The field, if any, is perpendicular to the surface.
13. perpendicular to the surface
14. Perpendicular to the surface.
15. Perpendicular to the surface
16. It is perpendicular to the surface of the conductor.

Question 3:

Answer:

1. Electric potential energy is just what it sounds like: it's the negative of the work done by the electric field over a distance r. Electric potential is the electric potential energy per unit charge.
2. Electric potential energy is the capacity of a charge to do work versus electric potential being the measure of this capacity.
3. electrical potential energy is the negative of the work done by a conservative force while electrical potential is the potential energy change per unit charge in moving from one point to another.
4. Electrical potential energy is calculated with a particular charge in mind; electric potential is computed based on the differences in field strengths (no outside charge is present).
5. the electric potential is the change in potential energy per unit charge, while electric potential energy is just the change in energy of a particle due to the electric field
6. Electrical potential energy is the change in energy that results from moving a charge from one point to another in an electric field. Electric potential is the potential energy change per unit charge in moving the charge from one point to another.
7. Electric potential is very simlar to electrical potential energy, as it represents a property of a force, but is slightly different, as it is the potential energy change per unit charge, as opposed to only the potential energy change.
8. Electric potential is the energy required to move a one unit positive charge between two points in an electric field. Electric potential energy is the energy required to move charge Q between two points in an electric field.
9. Electric potential is a measure for (electric potential energy/unit charge).
10. The electric potential is the electric potential energy change per unit charge
11. Electric Potential is the amount of potential energy per coulomb, where electric potential energy is the is the energy created by moving a charge, regardless of size, in an electric field.
12. Electric potential energy is the potential energy gained or lost by a specific charge when work is done on it in an electric field. Electric potential describes the difference in electric potential energy acquired by each unit of charge as work is done to move it from one point to another.
13. the electric potential difference is the change in potential energy per unit charge Moving a charge along potential difference decreases the charge's potential enegy
14. Electric potential energy is analogous to potential energy in a gravitational field, such as raising an object from the earth and having the potential energy increase. Electric potential is the actual potential enclosed in the charge, whereas the potential energy is the actual energy.
15. The electrical potential energy is the energy "stored" in a charge that exists in a field. The electric potential is the energy "stored" per unit charge.
16. One is the rate of the other (?)

Question 4:

Answer:

1. a) It tells you the change in potential energy per unit charge. Moving a charge through a positive potential difference is similar to moving a ball up a hill--the potential energy increases. Similarly, if you move a charge through a negative potential difference, the potential energy decreases. b) No, it doesn't, just like work is independent of path so is potential difference. This is because of the dot product. When r is perpendicular to E, r dot E=V=0, so only movement parallel to the field "counts" toward electric potential.
2. (a) The potential difference gives the voltage difference between these two points. (b) The potential difference does not depend upon the path between A and B. Its a state function. The ratio of the two distance is most significant.
3. (a) This is the change in potential energy per unit charge. The Delta V denotes this change. (B) Since potential difference is a property of two points, it does not depend on the path taken.
4. a. The difference in field strengths at two points. If B is higher, then it is positive, if A is higher, then it is negative. b. No, it only depends on the distance against the electric field (like work against a gravitational field).
5. a) the electric potential difference tells us the change in potential energy per unit charge, so the change in energy of a certain quantity of charge. This is used to express electric properties in terms that don't involve specific charges. The sign of delta V depends on if the path goes with or against the electric field. if the potential energy and charge is positive so is potential, while if potential energy is negative and the charge is positive the potential is negative b)No, because we're just concerned with starting and ending locations. It doesn't matter the path taken in between a and b
6. (a) The potential difference tells us the change in potential energy per unit charge. It also tells either the electric field strength or distance the object moved if one of those values is given. If Delta V is negative, then the change in potential energy is negative and the charge is moved some distance in the direction of the electric field. (b) It does not depend on the path taken as it is a property of two points. The path from A to B is not important, but the distance from A to B is, because the electric force is conservative.
7. (a) The potential difference tells you the work or energy per unit charge that is neccessary to move a charge between two points. Potential energy will increase, and thus yeild a positive potential difference, when moving a positive charge through a positive potential difference. It will be negative when a negative charge is moved through a negative potential difference. (b) The potential difference is path independent, meaning it does not take into account how the charges moved between the two points, as it is a property of two points and not of anything else.
8. (a) Potential energy increases when a positive charge is moved against a positive potential difference and decreases when it is moved along a negative potential difference. Thus, potential difference tells whether potential energy of a charge will increase or decrease if it is moved from one point to another in an electric field. (b) Potential difference doesn't depend on the path taken because potential is a characteristic of a point.
9. (a)Delta V tells us the change of potential energy per unit charge, made in the movement from A to B. (b)No, it doesn't matter how it moved because deltaV is the integral of E•dr.
10. a) change in potential energy per unit charge. the sign can be positive or negative b)It does not depend on the path, the potential difference is the same. This is like how the change in gravitational potential energy of a ball going down 3 feet does not depend on the path taken by the ball.
11. The potential difference tells how much energy is gained by moving a particle in an electric field from point A to point B. If the particle gains energy, deltaV is positive, and work is done to move the particle. If deltaV is negative, then the potential difference has decreased and energy has decreased. The potential difference does not depend on path, merely on the change in distance from the charge.
12. a) The potential difference tells you how much work per unit of charge it takes to move a charge from A to B. It also indirectly reveals the strength of the electric field, and the sign indicates the direction of motion relative to the field. Specifically, a negative potential difference means that moving from A to B moves in the same direction as the field, and a positive charge indicates motion against the field. b) The potential difference does not depend on path, because it is a function only of electrical potential energy, which is independent of path.
13. a) 1 V/C = 1 N/C, 1V tells me how much work does it need to move 1 coulomb of charge b) No, because the potential difference at point P is always a shortway to go
14. a) Potential difference tells what direction the charge moves as well as the direction and strength of the electric field; this is enclosed in the sign and value of the dV, a positive sign shows that the energy is decreasing and the charge is moving in the same direction as the field, but moving in opposite directions gets a negative sign. b) Potential difference does not depend on the path, just like with gravitational potential, the shortest path taken is the calculation, independent of the actual path taken.
15. a. The potential difference tells me how much work needs to be done to move a charge in a field. Moving a charge against a potential difference requires positive work, while moving with the potential difference will not. b. no, potential difference is a property of two points, not the path taken.
16. A) It tells us the potential energy change of a charge as it moves from A to B in an electric field. The sign depends on whether the path goes with or against the path. B)It doesn't depend on the path as it is a property of two points.

Question 5:

Answer:

1. You have to do a summation.... V=sigma (kq/r).
2. The potential difference between two points in the presence of a non-uniform electric field can be calculated by integrating the charges over the distance between the two points.
3. Use the integral by dividing the path into segments dr which give values of dV which is summed to give the total potential difference.
4. An integral (or sum) of fields at different locations must be taken.
5. An integral of the electric field dotted with dr, the many small changes in distance.
6. An integral must be taken. Specifically, the potential difference is equal to the negative integral of the dot product of the vectors E and dr.
7. In order to calculate the potential difference between two points in the presence of a non-uniform electric field, you must divide the field into smaller, straight fields and sum them, thus taking the integral.
8. We must divide the path into little segments dr in which the electric field is uniform at every point in that segment. Then we find the potential dV for every segments and sum up every dV to get potential difference.
9. We have to use -integral of E•dr from A to B.
10. An integral is needed to calculate the potential difference.
11. You must use a summation equation to sum all of the kq/r of the individual charges. This works due to superposition.
12. Integrate
13. we need to use integral to find the potential difference. we could divide the path into small segments that it's essencially straight with a uniform field
14. Just like calculating a non-uniform electric field in general, the potential difference in a non-uniform electric field is calculated using integrals, and the whole field is divided up into small pieces and then added together.
15. An integral must be used to find the potential difference.
16. We need to divide the path into segments dr each so short that it's essentially straight ans with an uniform field over it.

Question 6:

Answer:

1. Well, when you run or walk or even just sit on the couch watching tv, you burn calories. Calories are just a non-SI unit of energy and they're equal to about 4 joules. So no, one joule is not a lot at all. It's a quarter of a calorie, which is like five steps on the treadmill or like half a minute of law and order.
2. Opening a door could approximately be 1 Joule of work, although throughout our lives we do massive amounts of work, most of which measured in calories, which can be measured also in Joules; 1 Joule is not very much.
3. This is not a lot, and this would be the energy needed to lift a small fruit 1m up from a table.
4. Lifting a kilogram about 10 centimeters. It is not very much work.
5. Picking up 1 liter of water up to 1 meter. No, its not a lot.
6. Doing 1 Joule of work is about equal to lifting a small fruit 1 meter above the ground. This is not a lot.
7. An individual can exert one Joule of work by moving a small apple about one meter. This is very easy, and seems like relatively no work.
8. 1 Joule is the energy required to move 1 C charge 1 m against an electric field of strength 1 N/C. It's also equivalent to lifting 0.1 kg mass 1 m straight up. So, it's not a lot of energy.
9. Carrying an iPhone for a meter. Not really much.
10. Picking up a backpack off of the floor. Not a lot of work.
11. One Joule is the energy done lifting a one newton object one meter. For a human, this is not a lot of work.
12. Moving a small book from the desk to a shelf about 1m above the desk would do 1J of work. This is not a lot.
13. a 1V battery does 1J work on every coulomb of charge it moves
14. One joule is the amount of energy required to move one kilogram one meter in one second; it is not a lot of energy.
15. 1 Joule is approximately the energy required to lift a small apple one meter straight up. It is not very much work.
16. A joule is the energy required to lift a small apple one meter straight up. It's not a lot.

Question 7:

Answer:

1. I don't really know what this means...I guess, if you have two surfaces with equal potential, they're not going to have a field between them so there will be no field lines.
2. Field lines on equipotential surfaces are like contour lines on maps. To move perpendicular to the electric field lines require no work, like moving around a contour line on a map.
3. Electric field lines and equipotential surfaces have a constant electric field at a distance r from a charge.
4. In an equipotential surface, all fields intersecting it are equal (all field lines are of equal distance apart). Around a point charge, an equipotential surface would be a sphere.
5. electric field lines are uniform across equipotential surfaces
6. The closeness of electric field lines and the steepness of the equipotential surfaces both indicate the strength of the electric field. Closer electric field lines and steeper equipotential surfaces represent stronger electric fields.
7. Electric fields and equipotentials are perpendicular.
8. equipotential surfaces are surfaces perpendicular electric field lines.
9. Equipotential surface is a surface which is perpendicular to the electric field so that there is no electric potential difference between two points on the surface.
10. Equipotential surfaces are surfaces perpendicular to electric field lines.
11. Electric field lines connect areas of equipotent surfaces
12. A surface that is at right angles to the net electric field is an equipotential surface, because no work is done either by or against the field to move a charge along the surface.
13. on the equipotential surfaces the electric field lines have a uniform density
14. Electric field lines and equipotential surfaces are perpendicular.
15. Electric field lines and equipotential surfaces are perpendicular to each other.
16. Equipotential surfaces are surfaces on which there is no potential difference between two points on that surface.

Question 8: