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PHYS 296 - 04 LAB 3 ELECTRIC CHARGE Addison Gasser Shadi AlnaanahINTRODUCTION AND OBJECTIVES Lab 3 is over Electrical Charge, Electrical Fields, and their interactions. This lab specifically investigates the phenomenon of ‘static cling’, which is the tendency for light objects to stick (cling) to other objects due to static electricity. It is common in clothing, but occurs with other items, such as the tendency of dust to be attracted to, and stick to, plastic items. In this instance, it will be demonstrated using a tabletop, scotch magic tape, ‘soft’ fur, and a ‘hard’ rubber rod. There are four different parts (experiments A, B, C, D) that will be executed and analyzed. The overall objective for this lab is to become familiar with basic concepts of static electricity. For experiment A, a piece of Scotch Magic Tape, about 15 cm long, is pressed to a tabletop. Next, the tape is peeled from the table, and the non-sticky side of the tape is brought close to, but not in contact with, a very small scrap of paper. The results are discussed later in the report along with the other experiments. For experiment B, another similar piece of tape as described above is pressed to the table and peeled off. This second tape is brought close to the first tape, with no contact between the two. For experiment C, a piece of tape is pressed onto the table and designated with a “B” (for bottom) on it. Then another piece of tape is pressed on top to cover the B-tape and is designated with a “T” (for top). The pair of tapes is peeled off the table together as a unit. Next, the T and B-tapes are carefully separated. A T tape and B-tape piece are hung from the edge of the table. Then, another T-tape piece is brought to each piece, along with a B-tape piece brought to the other B-tape. Finally, for experiment D, a new B and T pair are obtained, along with a hard rubber rod and a piece of fur. The rubber rod isrubbed with the fur. Then, the rod is brought close to, without touching, the B tape and then, in a like manner, brought close the T- tape. ANALYSIS AND DISCUSSION QUESTIONS A 1. Describe the behavior of the paper. The paper became attracted to the non-stick side of the tape, even making a jump up to stick to the tape. 2. Describe the behavior of the tape as you bring objects toward it (e.g., a hand, a pen). As the object (i.e. hand) neared the non-stick side of the tape, the tape would move toward the object by attraction. B 3. For what reason could you say that the two pieces of tape had the same charge? The two pieces of tape have the same charge and repel, because both were designated with the same charge when ripped from the table. Due to either losing to or stealing electrons from the table. The same action was done for both pieces, so the same charge is given to both 4. Describe your observations and write your conclusion about like charged objects. Considering both pieces of tape were designated with the same charge, and they forced away from each other when brought near, a sound conclusion would be that like charges repel each other. 5. Why would it be important that only the second tape comes close to the first tape and nothing else? Because that would mean one tape is neutral while the other has a net charge. 6. Does distance seem to make any difference? Discuss. Yes, distance seems to make a difference. This would be because charged objects have a limited distance to which they can act on one another. The smaller the separation distance is, the more prominent the force of attraction/repulsion is. The greater the separation distance is, the less prominent the force of attraction/repulsion is.C 7. Describe the interaction between the following pairs of tape when they are brought near one another. Two T- tapes – The two top pieces of tape repelled each other. Two B- tapes – The two bottom pieces of tape repelled each other. One B-tape and one T-tape – The piece of bottom and piece of top tape were attracted to each other, attempted to ‘stick’ together. D 8. Compare the interactions of the rubber rod with B-tape and T-tape to the interactions between the tapes in part C. Discuss similarities and differences. When brought near, the rubber rod repelled the top piece of tape, and was attracted to the bottom piece of tape. The top tape, bottom tape, and the rod all have their own net charge (+ or -). The rod obtained its charge after frictional contact with the fur. In this aspect, it repelled the tape with the same charge, and was attracted to the tape with the opposite charge. Like how the two pieces of top and bottom tape were attracted to each other, as they had opposite charges. 9. Why are the two kinds of charge called positive and negative? This is because when equal amounts of the two different charges (+/-) are added (or present in a body), they cancel each other out. When a charged object (one with excess charge) is brought near a neutral object (one with equal amounts of both kinds of charge) the charge of the neutral object will be forced to redistribute. 10. What is the nature of the redistribution? Why does the charged object always attract the neutral object? The nature of redistribution is a result of polarization within an object. When a net charged object is brought near a neutral object (typically a conductor), it causes the charges in the neutral object to redistribute based on attraction/repulsion. This depends on if the net charge on the approaching object is positive or negative. Therefore, charged objects always attract the neutral. Because the opposite charges in the neutral object move toward the charged object.CONCLUSION The experiments performed in Lab 3 laid out a clear demonstration of how Electric Charge is distributed and how interactions between objects are influenced. Experiments A, B, and C gave a basis on how charges directly interact with each other. How like charges repel, and opposite charges attract. With experiment D, the fur and rubber rod perfectly showed how charge is passed from one object to another (through frictional contact by rubbing). And showed how polarization affects charge re-distribution in an

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