Reading Quiz

Question 1:

Describe a very simple experiment you can do to determine if your T tape is charged positive or negative (or alternatively if your B tape is charged positive or negative). Perform your experiment (if you can) and report your conclusion.

Answer:

We have a balloon. We know that rubbing a balloon on wool results in the balloon acquiring a negative charge. Bring a T tape and a B tape near the negative balloon. Whichever tape is repelled (or at least has the weakest attraction) to the negatively charged balloon must be negatively charged. The other tape then must be positively charged.
  1. You could charge up an object that is made of a material that distinctly prefers to obtain a positive or negative charge. Then hold this object near your tape and see if it attracts or repels. This will tell you the chage on your tape, but I am unsure of how to do this right here.
  2. In order to determine if your T tape is charged positive or negative you could hold the tape up to both ends of a battery to determine to which end the tape is attracted. When I did this, I had my T tape on top, and that tape was positive (it attracted to the negative pole of the battery).
  3. From balloon experiments, I know that my hair is positively charged after rubbing it with a balloon. When I brought the B tape to my hair, it was attracted to it. Since opposite forces attract, I know that the B tape must be positive.
  4. Stick the tape and smooth it down along a neutrally charged object like an index card. Then unstick the tape with one swift motion and put it close something with a positive charge. If it is attracted to the object with a positive charge then the T tape has a negative charge. If it repels, then the T tape has a positive charge.
  5. Charge a piece of wool by rubbing it against a comb. The wool shouls receive a positive charge. Hold the T tape and B tape up to the wool seperately. The negatively charged tape should be attracted to the wool, while the positively charged tape should be repeled. The T tape was attracted to the wool when I performed the experiment. This means that it should be negatively charged and the B tape should be positively charged.
  6. When you rub a balloon with a piece of cloth like wool, the balloon becomes negatively charged. To deterimine which piece of tape is positive or negative, put each one near the balloon. If it is positive, it will attract; if it is negative it will repell. T attracted so it is positive; B repelled so it is negative.
  7. I took a sock that was just out of the dryer and put each of the tapes up to the sock. The "T" tape ended up being attracted and the "B" tape was repelled.
  8. You can hold your T tape near an object that you know to have a positive or negative charge, and then see whether the tape repels or attracts. If it repels, it has the same charge, if it attracts, it has the opposite charge. For example, you could hold it up to the Van de Graaff generator, which you know is negatively charged, and see whether it attracts or repels.
  9. I could make my hair wet and see whether or not the strip is attracted to it because the book said that wet hair and clothing are usually negatively charged. When I did this, both strips were positively charged because they were both attracted to the hair and they repelled each other.
  10. I assume you're referring to tapes that were given out on Fri. I was absent on Fri so I'm also assuming I have no real clue how to answer this question.
  11. I think first you would need to have some charged object that you knew was positive or negative, otherwise you would only be able to tell if something was charged, not necessarily whether it was charged positively or negatively...maybe I'm just not thinking creatively enough.
  12. charge an object that is prone to either gaining or losing electrons. A material at a very far end of the spectrum will be most useful. Now that you know which charge this object has you can find out the charges of the tape. If the object you charged up has a negative charge, then tape that is attracted to it is positive, and tape that is repeled from it is negative.
  13. If I bring my T tape up to the positive or negative end of a battery, it will either attract or repel. This should tell me the charge of the tape. When I tried this, my T tape was attracted to BOTH the positive and negative ends of the battery, and my B tape was repelled from both the positive and negative ends. What does that mean?
  14. To determine how your tape is charged, charge a balloon by rubbing agaist a wool sweater. This charge is definitely negative. Put the tape near the balloon. If it is attracted to the balloon, the tape is charged positively. If the balloon repels it, then they are both negative.
  15. With the T tape and B tape set up as we did in class, pull the T tape off and then the B tape off- both pieces of tape have the same charge and repel. Then put the two pieces of tape together and rip them apart again- hopefully one will steal negative charges from the other, leaving one tape with extra negative charges. If we then rub a balloon in our hair to give it negative charge and bring both pieces of tape near it, which tape is repelled by the balloon has negative charge and whichever tape is attracted to the balloon has a positive charge. I tried to perform this experiment however when I brought the tape near the balloon it seemed like both were attracted...maybe I neutralized the tape by mistake. I could not verify my hypothesis.
  16. You can move the tape towards an opject that you know is positively or negativly charged, and if the tape moves towards it, it has the opposite charge of the object, since opposite charges attract.
  17. You could rub your sneaker accross the carpet and that would give it a positive charge. Then you could put the tape up to the sneaker and if they repel the tape is positive and if they attract it is negative. Unfourtunately I wasn't able to perform the experiment.
  18. The top tape is positive and the bottom tape is negative. I found this by bringing a piece of (negatively charged) styrofoam near each piece. The T was attracted to it and the B was repelled by it.
  19. Well if you had a magnet with the two sides marked as either positive or negative, you could put the tape next to the negative side of the magnet and if it attracted to the magnet you would know it was positive, or vice versa.
  20. A simply experiment you could to to determine if your T tape is positively or negatively charged would be to place the T tape next to a negatively charged object, say a balloon that you charged and observe it the tape is attracted or repulsed.
  21. Get a 12V battery and place the T tape next to the positve end and the negative end and see which one it is attracted to and which one it is repelled from. Based on this you can tell what the charge of the tape is. Then perform the same task to determine the charge of the B tape.
  22. I guess this was something that was done in class that I missed...I will have to talk to you about it in class.

Question 2:

In your own words, describe electrostatic potential energy (we'll usually just call this electric potential energy). In your description, make sure to compare/contrast with gravity potential energy.

Answer:

Your responses below.
  1. Electrostatic potential energy is the potential energy due to electrostatic forces. This energy is prevalent when two like charges are forced together or two oppositely charged objects are pulled appart. The force of attraction or repelling that is stored when you pull or push the objects in the directions opposite their natural tendency is the potential energy that is stored. This is a lot like gravity potential energy in that you do work to obtain potential energy by working counter to the natural force. However, unlike gravity potential energy, electric potential energy can be found in any direction, not just down.
  2. Electrostatic potential energy is that energy stored in the electrostatic forces between two objects, therefore depends on the charges of the objects (analogous to mass when looking at gravitational potential engery), the Coulomb constant (like g), and also the distance between the two objects (similar to the distance between an object and the ground). Similar to gravitational potential energy, electrostatic potential energy is released from a positive voltage (height above the ground) but energy is needed to change from a negative voltage to a neutral one (like gravitational potential energy increases as an objest is raised higher above the ground).
  3. Electric potiential energy is the energy it gains when it is forced near something it usually repels or forced away from something it usually attracts. When an object is allowed to attract and repel other objects naturally (like when an object is allowed to fall to rest), its electric potiential energy is zero (like the gravitational potiential energy is zero). However, when you do work on these objects to force them away from what's natural, that's when they gain these potiential energies.
  4. Electric potential energy happens when opposite charges are separated or when like charges are put together. Similar to gravity potential energy, charge tends to flow from higher voltage to lower voltage. The more charge, the more potential energy.
  5. When you pull two objects which are attracted to each other apart (opposite charges) or push two objects together which are repeled, your energy from doing work is converted into electrostatic potential energy. That electrostatic potential energy is pulling the objects back towards each other or pushing them back apart, and if you let go, that's what would happen. This is similar to gravity potential energy because the amount of energy is directly related to the location of the objects. (The higher you lift a ball and the further you pull apart a sock and a shirt, the more potential energy exists in the system.)
  6. Electric potential energy is the stored energy from pushing two opposite charges apart, or pushing two like charges together. It is similar to gravity potential energy because when the voltage is positive, it doesn't need any more enery to become nuetral. That is similiar to the gravity potential energy of an oject that is high. When voltage is negative, it needs energy in order to become neutral. This is similar to an oject onthe ground, becuase engergy is needed in order to pick it up.
  7. It is energy stored in the forces. It occurs when the same charges are pushed together, or when opposite charges are pulled apart.
  8. Electrostatic potential energy is the energy between two charged surfaces as they are separated. It is the same in that both gravity potential and electrostatic potential energies rely on distance between two objects, but gravitational potential depends on the distance from the earth, while electrostatic depends on the distance between the charged objects.
  9. Electric potential energy occurs when two attractive forces are pulled apart. The energy stored between these forces is the electric potential energy. It is similar to gravity potential energy because in electric potential energy, charges move from high voltages to low voltages, just like how objects with gravity potential energy move from high altitudes to low altitudes.
  10. The energy that you exert on two charged objects in order to keep them from coming together or repelling is made into electrostatic energy. Altitude does not effect electic potential energy but it does effect gravity potential energy.
  11. Electrostatic potential energy depends both on the charge of an object (or objects) and their proximity to each other. When two things are closer together, they have a much greater attraction to or repulsion from each other and therefore their electrostatic potential energy is greater. It's similar to gravity potential energy, because it's really a measure of the energy between two objects- regarding gravity, it's between the earth and an object, and regarding electrostatic it's between a charged object and another charged/uncharged object. They are different because where gravitational potential energy increases with distance (height), electrostatic potential energy decreases.
  12. Electric potential energy is potential energy that an object gains when work is done to it. Much like gravitational potential energy, when two objects are separated from one another, and opposite charges are separated or like charges pushed together, the work done to separate or join them is stored in electrostatic potential energy. This is like gravitational potential, because when work is done to separate an object from the earth, energy is stored in gravitational potential energy.
  13. Electrostatic potential energy deals with the charge on objects and how likely it is for charges to attract or repel. For example, an object with a large (positive or negative) charge is more likely to be strongly attracted to or strongly repelled from another charged object, than a an object with a small charge is. Similarly, an object has a large gravity potential energy at a higher height than at a lower height.
  14. Electrostatic potential energy describes the potential for a charge when two objects come into contact (rubbing, touching, ect.); it is caused by an exchange of electrons. Like gravitational potential energy, it decreases as the kinetic (or electric) energy increases.
  15. Electrostatic potential energy is the potential energy stored between electric charges and is strongest when like charges are close together or opposite charges are far apart. This is like gravitational potential energy in that a positive charge releases electrostatic energy when it moves some distance away, and an object loses gravitational potential energy to kinetic energy when it moves some distance toward the surface of the earth. However gravitational potential energy deals only with vertical distances, while electrostatic potential energy does not depend on direction, just distance between charges.
  16. It is the potential energy when two opposite charges are moved apart, or two like charges are moved together. Electostatic potential energy is characterized by voltage which is similar to gravitational potential energy in that voltage travels from an area of high voltage to an area of low voltage.
  17. Electrostatic potential energy is the amount of energy in the forces that result from difference in charges for objects. The amount of energy in this case is equal to the amount of energy that is needed to be added to the system to overcome the strength of the force.
  18. When there are forces that result from static interactions, this kind of energy is stored from the interactions that happen. It is different from gravitational potential energy because it is not affected by height. It is similar in that they are both stored energy.
  19. The electrostatic potential energy is the amount of energy it took to do the work on the two objects that seperated them by the distance they currently are from each other. So if they're 5 cm apart its the amount of energy it would take to seperate the two objects by 5 cm. Its like gravity potential energery because gpe is determined by the amount of work it would take to raise the object in question to the height it currently is at.
  20. Electrostatic potential energy is present whenever like charges are pushed together, or opposite charges are pulled apart. This is different to gravitational potential energy because it does not relate to hieght or gravity, but rather to forcing the charges to do something they would normally not do or do not want to do (like be split apart, when the charges oppositly charged.
  21. Electrostatic potential energy (EPE) is the energy stored in a charged object. You can see EPE when you pull opposite charges apart or push like charges together. It is the work you have to do on charges to make them do what they do not want to do. EPE and gravity potential energy (GPE) are both conserved. GPE is a measure of the amount of energy present in an object when it is at rest, while EPE is a measure of the amount energy needed to make charges due the opposite to what they naturally want to do (like charges pushed together and opposite charges pulled apart).
  22. It is the energy present when oppositely charged objects are pulled apart from each other or objects with the same charge are pushed toward each other. In other words, they have the potential to want to move toward each other or away from each other. They get greater with distance just like gravity potential energy.

Question 3:

Experiment time again! This time, charge up your balloon someplace very dark and very quiet. Pay attention to what you hear and what you see during the charging process. Report any observations. (You'll probably need to be someplace pretty dark to see anything - maybe a bathroom or a closet?, but you'll probably be able to hear something).

Answer:

I did this in my bathroom with the lights off and the curtains drawn. The light in the hallway was off. When I rubbed the balloon on my wool sweater, I heard some very loud crackling and I saw some very bright sparks! Wow!
  1. You can hear a sort of crackling noise when you rub the balloon and see a few little sparks if you look closely. this is due to the charges building up on the balloon and when they get too strong for the air, they spark.
  2. When I charged my balloon on my fleece in the dark, I did hear faint crackling and snapping sounds, and I saw tiny sparks of light. This light was the result of electrostatic energy that had accumulated as I charged my balloon being released. This occurred when the surface of the balloon at the particular spot the spark occurred was very close to the fleece but not touching it. At that location with a large electrostatic force, the air could not handle the force, so the spark formed in order to get rid of the electrostatic potential energy as light, sound, and also heat.
  3. When I charged up my balloon, I heard crackling and I even saw a spark or two.
  4. While I was rubbing the balloon around you could hear small cracking noises. I also thought I saw tiny sparks.
  5. The balloon made a crackling sound as it was charged and I saw a little bit of sparking.
  6. I heard crackling and saw some sparks between the balloon and the cloth.
  7. When I charged up the balloon, I head a kind of "crackling" noise when I ran the balloon over the surface.
  8. You can hear crackling noises as the balloon becomes charged, and I thought I saw small sparks between the balloon and my sweater, but it was hard to tell.
  9. I could hear a lot of crackling and of course the sound produced by the friction of rubbing the objects together. I was not able to see anything.
  10. You can hear some crackling noises and I think I can kind of see some sparks.
  11. I rubbed my balloon on a particularly static-prone vest that I have, but I still couldn't see anything happening. I did hear some faint crackling though.
  12. I was not able to see anything note worthy while charging my balloon, although I heard a crackling noise when I pulled the balloon away from my wool sock.
  13. Maybe I imagined this, but I thought I saw a tiny spark. I think I also heard a faint crackling sound.
  14. I heard and saw sparks. I sparks looked like tiny blue flashes of light.
  15. In my dark and quiet bathroom, after charging up the balloon I touched my finger to it and heard a slight cracking/zapping noise and saw a small spark of light between my finger and the balloon.
  16. You can hear the static electricity and if you look closely you can see blueish white shocks.
  17. I heard a slight bit of crackling.
  18. I think that I saw small sparks. I heard noises that the sparks made, which I don't really know to describe. They were not very loud, and sounded like short outbursts of electricity.
  19. You can hear a crackling noise and I suspect that what you might be able to see (I couldn't) was small little sparks.
  20. As you charge the ballon in a dark, and quiet environment, you can hear a crackling sound, and occationally you can see sparks of light.
  21. I heard some minor crackling and then some sparks as I rubbed the balloon against my shirt to charge it.
  22. I used my shirt to charge the balloon and you could hear the static between the two objects. It was really cool because after a few seconds it created sparks between the objects.

Question 4:

What concepts or equations from the reading did you find confusing? What would you like us to spend class time discussing further?

Answer:

Your responses below.
  1. I think I understand everything so far.
  2. I'm a bit confused about voltage... the analogy to water didn't help me too much.
  3. I didn't really understand what causes charge in the first place.
  4. the difference between tires on antique and modern tires
  5. I don't really get how you can change insulators into conductors.
  6. nothing at this time
  7. I was confused when they said that negatively charged detergents are best, but then positively charged detergents are good too.
  8. I'm having difficulty understanding exactly what electric potential energy is, and how to measure voltage.
  9. When we were playing with the tape and the small piece of paper in class on Friday, most people saw that both pieces of their tape were equally attracted to the little piece of paper. One of my pieces of tape though was clearly repulsive to the paper-. I think it might have been because I had my piece of foil lined up exactly on top of the piece of paper, and maybe it picked up some charge when I pulled the foil off of it? Could please offer an explanation as to why my tape might have acted differently?
  10. I understand all concepts from this reading.
  11. This isn't really from the reading, but question 1 (see above).
  12. None :)
  13. I would like to discuss the positively/negatively charged detergents that were talked about in the reading.
  14. i think i would like to understand voltage better
  15. I was confused with voltage and the strange analogy the author presented.
  16. none
  17. I think I understand this.
  18. I was confused with the concept of voltage and the manner in which they compared it to water.
  19. how to figure out the charge of the T and B sticks in the expermient, and the concept of EPE.
  20. I didn't understand how fabric softeners work in turning insulators into conductors.

Question 5:

What material from previous classes are you still having difficulty with?

Answer:

Your responses below.
  1. I'm okay at this point.
  2. I'm okay with previous material.
  3. Everything from the last lecture was pretty clear.
  4. none
  5. nothing
  6. nothing at this time.
  7. Nothing
  8. -
  9. I understand all concepts from previous classes.
  10. None.
  11. None
  12. The T tape B tape experiment.
  13. i think im good
  14. nothing really.
  15. none
  16. Still got it.
  17. I was still slightly confused about the concept of polarization.
  18. why do both the postive and negative charged sticks get attracted to the neutral sheet of paper?
  19. I don't really understand how charge transfer works.