Homework_01

Homework_01 - Nguyen Thanh Homework 1 Due 7:00 pm Inst...

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Nguyen, Thanh – Homework 1 – Due: Jan 22 2008, 7:00 pm – Inst: Weathers 1 This print-out should have 8 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. The due time is Central time. 001 (part 1 oF 1) 10 points 1) Two uncharged metal balls, Y and X , each stand on a glass rod and are touching. X Y 2) A third ball carrying a positive charge, is brought near the frst two. X Y + 3) While the positions oF these balls are fxed, ball Y is connected to ground. X Y + 4) Then the ground wire is disconnected. X Y + 5) While Y and X remain in touch, the ball carring the positive charge is removed. X Y 6) Then ball Y and X are separated. X Y AFter these procedures, the signs oF the charge q Y on Y and q X on X are 1. q Y is neutral and q X is positive. 2. q Y is neutral and q X is negative. 3. q Y is negative and q X is negative. cor- rect 4. q Y is negative and q X is positive. 5. q Y is negative and q X is neutral. 6. q Y is positive and q X is positive. 7. q Y is neutral and q X is neutral. 8. q Y is positive and q X is neutral. 9. q Y is positive and q X is negative. Explanation: When the ball with positive charge is brought nearby, the Free charges inside Y and X rearrange themselves. The negative charges are attracted and go to the right ( i.e. move to X ), whereas the positive charges are repelled and collect in the leFt hand side oF the system Y Y , i.e., in Y . When we ground Y , the positive charges which have collected in Y are allowed to es- cape (they strive to the leFt), whereas the negative charges in X are still held enthralled by the positive charge on the third ball. We break the ground. Now we remove the third ball with positive charge. The charge on X is redistributed in the system Y Y , i.e. they share the negative charge (equally iF identical). ±inally we separate Y and X . The signs oF the charge on Y and that on X are both negative. keywords:

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Nguyen, Thanh – Homework 1 – Due: Jan 22 2008, 7:00 pm – Inst: Weathers 2 002 (part 1 of 1) 10 points Four point charges, each of magnitude 15 . 18 μ C, are placed at the corners of a square 79 . 2 cm on a side. The value of Coulomb’s constant is 8 . 98755 × 10 9 N · m 2 / C 2 . If three of the charges are positive and one is negative, ±nd the magnitude of the force experienced by the negative charge. Correct answer: 6 . 32011 N. Explanation: Let : k e = 8 . 98755 × 10 9 N · m 2 / C 2 , d = 79 . 2 cm = 0 . 792 m , and Q = 15 . 18 μ C = 1 . 518 × 10 - 5 C . F
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This note was uploaded on 10/24/2011 for the course PHYS 2220 taught by Professor Littler during the Spring '00 term at North Texas.

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Homework_01 - Nguyen Thanh Homework 1 Due 7:00 pm Inst...

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