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Unformatted text preview: song (shs546) Practice HW 1 Solutions weathers (22202) 1 This printout should have 6 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points Two metal spheres that are initially un charged are mounted on insulating stands, as shown. X Y A negatively charged rubber rod is brought close to but does not make contact with sphere X . Sphere Y is then brought close to X on the side opposite to the rubber rod. Y is allowed to touch X and then is removed some distance away. The rubber rod is then moved far away from X and Y . What are the final charges on the spheres? Sphere X Sphere Y 1. Negative Positive 2. Negative Negative 3. Positive Negative correct 4. Positive Positive 5. Zero Zero Explanation: The force is repulsive if the charges are of the same sign, so when the negatively charged rod moves close to the sphere X , the neg atively charged electrons will be pushed to sphere Y . If X and Y are separated before the rod moves away, those charges will re main on X and Y . Therefore, X is positively charged and Y is negatively charged. 002 10.0 points 1) Two uncharged metal balls, X and Y , stand on glass rods and are touching. Y X 2) A third ball, carrying a negative charge, is brought near the first two. Y X 3) Then the first two balls are separated from each other, Y X 4) and the third ball is finally removed. Y X When this is all four steps are done, it is found out that 1. Balls X and Y are both positive. 2. Balls X and Y are both negative. 3. Ball X is positive and ball Y is negative. 4. Balls X and Y are still uncharged. 5. Ball X is negative and ball Y is positive. correct Explanation: When a negative ball is moved near a metal lic object ( X and Y ), the negative charge will attract positive charges, causing X to have excess negative charge and Y to have excess positive charge ( X and Y are in contact, so the total net charge on X and Y should be zero). song (shs546) Practice HW 1 Solutions weathers (22202) 2 + Later, X and Y are separated, retaining their charges, so when the third ball is finally removed, X will have net negative charge and Y will have net positive charge....
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 Spring '00
 Littler
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