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Unformatted text preview: carroll (arc2632) – Homework 01 – yao – (92945) 1 This printout should have 21 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Two uncharged metal balls, Z and X , stand on insulating glass rods. A third ball, carrying a negative charge, is brought near the ball X as shown in the figure. A conducting wire is then run between Z and X and then removed. Finally the third ball is removed. X Z − conducting wire When all this is finished 1. balls Z and X are still uncharged. 2. ball Z is negative and ball X is neutral. 3. ball Z is neutral and ball X is negative. 4. balls Z and X are both negative. 5. balls Z and X are both positive, but ball X carries more charge than ball Z . 6. ball Z is negative and ball X is positive. correct 7. ball Z is positive and ball X is negative. 8. balls Z and X are both positive, but ball Z carries more charge than ball X . 9. ball Z is positive and ball X is neutral. 10. ball Z is neutral and ball X is positive. Explanation: When the conducting wire is run between Z and X , some negative charge flows from X to Z under the influence of the negative charge of the third ball. Therefore, after the wire is removed, Z is charged negative and X is charged positive. 002 10.0 points A strong lightning bolt transfers about 26 C to Earth. How many electrons are transferred? The charge on an electron is − 1 . 60218 × 10 19 C. Correct answer: 1 . 62279 × 10 20 . Explanation: Let : q = 26 C and q e = − 1 . 60218 × 10 19 C . The charge is proportional to the number of electrons, so q = n  q e  n = q  q e  = 26 C − 1 . 60218 × 10 19 C  = 1 . 62279 × 10 20 . 003 10.0 points Two identical positive charges exert a repul sive force of 6 . 1 × 10 9 N when separated by a distance 3 . 8 × 10 10 m. Calculate the charge of each. The Coulomb constant is 8 . 98755 × 10 9 N · m 2 / C 2 . Correct answer: 3 . 1306 × 10 19 C. Explanation: Let : F = 6 . 1 × 10 9 N , d = 3 . 8 × 10 10 m , and k e = 8 . 98755 × 10 9 N · m 2 / C 2 . The electric force is F e = k e q 1 q 2 d 2 d 2 F e k e = q 2 q = radicalBigg d 2 F k e = d radicalbigg F e k e carroll (arc2632) – Homework 01 – yao – (92945) 2 = (3 . 8 × 10 10 m) × radicalBigg 6 . 1 × 10 9 N 8 . 98755 × 10 9 N · m 2 / C 2 = 3 . 1306 × 10 19 C . 004 10.0 points Object A and object B are initially uncharged and are separated by a distance of 1 meter. Suppose 10,000 electrons are removed from object A and placed on object B, creating an attractive force between A and B. An addi tional 10,000 electrons are removed from A and placed on B and the objects are moved so that the distance between them increases to 2 meters....
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 Spring '10
 TSOI
 Physics, Charge, Electrostatics, Work, Electric charge, Carroll

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