Reading Quiz

Question 1:

Answer:

2. No. The object contains many charges, but it has an equal amount of positive and negative charges so that the total charge is nuetral.
3. No, an electrically neutral object still has charges, but it is neutral because it contains an equal amount of both positive and negative charges. Since they have an equal amount, niether one is stronger so we say that it has no net charge.
4. No, the object still contains charges, but these positive and negative charges are in equal amounts and balance out.
5. No, it just means that the negative charges equal the number of positive charges.
6. No, all objects contain both positive and negative charges: protons and electrons. However when the object has the same amount of protons as electrons, the positive balances out the negative, making the object as a whole electrically neutral.
7. No, the object may have millions of charges but it means that the total number of positive charges is exactly equal to the total number of negative charges.
8. No. It is still composed of atoms, which are composed of protons and elctrons (and neutrons) which are charged particles. A neutral object only means that the number of charged particles in the object is equal and thus they all cancel each other out.
9. Although this object would have not net charge, this does not mean the object contains no charges. All matter has electric charges within it, however the positive and negative charges are balanced which makes the net charge 0, meaning the object is neutral. (This is similar to the net force on an object being zero, therefore having no acceleration. Although the net force is 0 -- such as when moving at constant velocity -- there are still the forces of gravity, the support force which forms Newton's 3rd Law pair with gravity, the force of friction, as well as the force of the motor or whatever is moving the object all acting.)
10. It has a zero net charge. This means the something else much have either added electrons or removed protons or done done both.
11. It doesn't mean that the object contains no charges. It means that the charges of the object are equal so they cancel each other. There is not one charge that dominates the other.
12. No, everything has many positive and negatively charged particles. If an object is neutral, that just means that it has an equal number of positively and negatively charged particles.
13. No net charge simply means that the amount of positive and negative charges in the object are equal. So an electrically neutral object does contain charges.
14. No, there are always protons, neutrons, and electrons. When an object is neutral, it means the positive and negative charges sum to zero (are equal and opposite).
15. NO, if an object has no net charge it simply means that the amount of positive and negative charges (protons and neutrons) are the same.
16. No, neutral is referring to the net charge of the object. The object in reality is made up of many pieces, some of which are positive and others which are negative, together these pieces combine to have a net charge of 0.
17. It doesn't mean that the object contains no charges; however, it means that the number of positive charges and the number of negative charges are equal and balance each other out, thus resulting in no net charge.
18. No - it just means that the sum of all of its positive and negative charges is zero; the charges are in equilibrium.
19. No, each object is made up of atoms that consist of neutrons, protons, and electrons. Protons are positively charged, electrons have a negative charge, and neutrons have no charge. These charges exist within all objects, and for an object to have no net charge means that it has the same number of protons and electrons.
20. The object still has protons and electrons, it's just it has the same amount of both, so the charges cancel out.
21. No, it means that the negative and positive charges are equal.
22. If an object is electrically neutral it has no net charge becuase it has the same number of protons as it does electrons, which are opposite charges that offset each other.
23. No, that just means that the sum of all its positive and negative amounts of charge equals zero.

Question 2:

Answer:

2. Coulombs law states that the force on each charge varies inversly with the squar of their separation, so if you increase the separation by 5 times, then the force will decrease by a factor of 25. The new force will be .0004 N.
3. We can use Coulomb's equation F=(kq1q2)/r^2 to find the charges of the socks. When we plug in .01 for the force and .01 for r, using 8.988x10^9 we can find that the top half of the equation will always be 1x10^-6. Then we can plug in the new radius underneath to find that the new force between the socks is about 4x10^-4 Newtons.
4. 4Xx10^-4 Newtons
5. F=.002 N
6. They will now repel each other with a force of 0.04 N. Since F = (kC1C2)/r^2, .01 N = (kC1C2)/(.01m)^2, so (kC1C2)= .01. Therefore at .05 m, F = .01/ (.05m)^2, and F = 0.04 N.
7. 8.988x10^9 x 1.11358575x10^-12 ______________________________ = .00040035 N 5^2
8. since the equation uses the distance squared, the force will be 1/25 of its previous value, or .0004N
9. The socks will now exert a force of 0.0004N on each other if the only thing changed is the distance between them (r in the equation F = (k q1 q2)/r sq.)
10. 4.601856 x EE-27
11. They would now exert a force of .0004N on each other.
12. They will repel with 1/16th the force they did before, since they are now separated 4 more centimeters, so .00065N
13. The charge on each sock is .000001. When the distance is increased to 5cm the force exerted on each other is .00036N.
14. The force they now exert is .0004 N. (1/25 the original force because the coulomb constant and the objects charges did not change and the distance was multiplied by 5 and the distance is squared in the force equation).
15. They will now exert a force of 0.0004N.
16. .0004 N (note in the problem on the internet the force is .01 N. In the book the force in the problem is .001 N, .01 N was used as the force.
17. I'm not sure how to do these problems (see answer to question 4).
18. since I got a positive answer, the two socks will repulse one another.
19. .0004 N Increasing the distance by a factor of five will decrease the force by a factor of 25.
20. .01= [(8.988x10^9)x (q1) x (q2)]/ .01^2, (q1) x (q2) = 1.11x10^-14 sqroot(1.11x10^-14) = 1.05x10^-7 so F= [(8.988x10^9)x(-1.05x10^-7)x(1.05x10^-7)]/(5^2) = -3.96 x 10^-6 N
21. They will exert a force of .002 N on each other.
22. .002N
23. I think the force will be 1/25th the original force...so it should be 0.0004N.

Question 3:

Answer:

2. The balloon attracted the water. This means that the water had to have an electrical charge, since opposite charges attract eachother. It could also have been nuetraly charged, but polarized by the strong charge of the baloon.
3. The stream of water is pulled toward the balloon. My guess is that the water doesn't have a charge. We know that the balloon is charged, because we charged it and we can tell because it sticks to everything. Kind of like we saw in class, the balloon was even attracted to other uncharged balloons, so it's probably just as attracted to uncharged water. And since the force of the water acting on the balloon is equal to the water on the balloon due to Newton's third law, the water is pulled toward the balloon and not just vice versa. The water is neutral, but the proximity of the charged balloon causes the charges in the water to separate so that the attractive charges are closer, and the repellant forces are further away.
4. The stream of water bends in the direction of the balloon. This is caused by the electric charge of the balloon, which is evidently opposite of the stream of water since they atract. Rubbing the balloon gave or took electrons, and so the net electric charge is negative. The positively or neutrally charged stream of water then bent towards the negatively charged balloon.
5. The water bends towards the balloon. The water does not have a net electrical charge but is instead electrically neutral. Even though it has a zero net charge, the water still contains positively and negatively charged particles. When the balloon is brought close to the water, the negatively charged particles are attracted to the positively charged ones and the water bends.
6. The stream of water is attracted to the ballon and curves otuward toward the balloon. This does not mean the water has net electrical charge. Even if the water is electrically neutral, it may be attracted to the balloon since the balloon is electrically charged. As the example in the book with the sock and the neutral wall, the water can develop an electric polarization, remaining neutral overall but with the psoitive charged region nearest the negatively charged balloon.
7. The stream of water pulls towards the charged pen, meaning that the water must have a net electical charge that is inverse to the net electrical charge of teh pen. So if the pen has a negative net electrical charge, then the water must have a positive net electrical charge, which explains why they attract one another.
8. The charged balloon attracts the water. The water does not have an electrical charge. Only, the balloon has a net charge, and attracts the oppositely charged particles that are present in the water.
9. As the charged balloon is brought near the stream of water, the water is attracted to it, therefore its path arcs in that direction. The balloon does have a net electrical charge as a result of charging it through rubbing it against material, and when brought close to the water this makes the water acquire a net electrical charge as well (through induction since the balloon and water do not touch). However as the water flows out of the faucet initially, it does not have a net electrical charge, it simply contains both positive and negative charge. As the balloon approaches, the charges opposite those on the balloon (so positive if the balloon is negatively charged) are attracted toward the balloon and the like charges contained in the water (negative) are repelled.
10. The water "bends" from the straight sream that was flowing previously. I believe the wzter does have an electrial charge, because balloon carries an electric charge in it and transferrs net electrical charge to the water.
11. The water moves closer to the balloon. It doesn't mean the water has a net electrical charge. The positive parts of the water could move closer to the balloon and the negative parts would move further away.
12. The stream of water is pulled towards the balloon instead of falling vertically. This doesn't mean the water necessarily has a net charge. If the balloon were negatively charged, the positive particles in the water would be drawn towards the balloon and the negative particles would be pushed towards the other side. However the net charge in the water would remain neutral.
13. The water does not fall straight down as it usually does under the influence of gravity. Instead the stream bends, and falls at an angle. This does not mean that the water is charged. If the baloon is charged, it can still attract a neutral object.
14. The stream of water bent towards the charged balloon. This doesn't mean the water has a charge, but in every neutral object there are protons and electrons. When a charged object is brought near the neutral substance, the protons and neutrons rearrange. The neutral substance is then said to be polarized and there is attraction between the polarized and charged object.
15. As you place the charged balloon under the stream of water, you see that the stream of water is repulsed or moves away from the balloon, and does not touch the balloon. This means that the water does have a net electrical charge because since the balloon is given a net electrical charge, and it repulses when you try to put them together, this means that both the water and the balloon have the same charge.
16. First of all that was really cool. The stream of water actually bent towards the balloon. The water must have a net positive charge because by charging the balloon you are making it negative and positive is attracted to it.
17. This was really cool! I used a plastic comb, as I truly cannot blow up a balloon. I rubbed the comb against my hear, and when I put it near the thin stream of water, the stream moved toward the comb, so it looked like water was coming out of the stream at a diagonal. I'm not exactly sure why this happened--I know that water has electrolytes in it, so I think that has something to do with it. A question: why was it important that the stream of water was so thin? I tried the experiment again with a thicker stream of water and it didn't have the same effect.
18. The stream of water bends toward the negatively charged balloon - the electrical force is attractive. Since water is a conductor of electricity, its protons will try to get as close to the balloon as possible, while the neutrons will travel in the opposite direction. This makes the water have a positive net electrical charge.
19. The stream of water is attracted to the balloon and bends towards it. This does not necessarily mean that the water has a positive or negative net charge, because the charge of the balloon could be attracted to the positive or negative charges within the water, even if there is no net charge. Neutral objects are still attracted to charged objects.
20. no it just means that water is polar. The electrons in the water migrate away from the balloon so the protons in it end up attracting to the balloon.
21. The water bends toward the balloon. No this does not mean that the water has a net electrical charge because water is a well-known neutral substance. yet it still has the capacity to exert attractive forces on other materials. In biology, we learned about the polarity of water molecules, so I am guessing it has to do with that.
22. the water bent towards the pen!...(that was really cool by the way)... the pen became charged and the water obviously had the opposite charge and hence was attracted to the pen.
23. The balloon actually attracted the water to it. Yes the net electrical charge must be positive because the two objects attract each other.

Question 4:

Answer:

2. I would like to go into chemical potential energy a little bit.
4. #2 if I got it wrong
5. I don't understand how something gets a positive charge versuss a negative charge and vice versa.
6. Can we talk about chemical potential energy?
7. I still feel like I get it all.
8. How do charges get transfered from one object to another, like how does the balloon get its charge?
9. I understood this section.
10. nothing at this time.
11. I don't really get chemical potential energy.
12. Nothing
13. I understand all of the concepts from this reading.
14. I understood the reading but I'm looking forward to our discussion because there a lot of interesting applications.
15. I was still a little confused about how and why charge gets transfered from one object to the other.
16. Nothing really.
17. I don't understand why Ben Franklin called "what appears on glass when it's rubbed with silk 'positive charge' and what appears on hard rubber when it's rubbed with animal fur 'negative charge.'" Also, I was confused about check your figures #1. It is clear which equation to use, but I don't know what the values would be for q1 and q2--1N?
18. Coulomb's Law equation
19. -
20. --
21. none.
22. coulombs law
23. I think I understood everything in the reading. However, I am a little unsure of my answer in question #2.