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chapt 1

# chapt 1 - PHYS 133 WEEK 1 CHAPTER 25 25.2 Model Use the...

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PHYS 133, WEEK 1 CHAPTER 25 25.2. Model: Use the charge model. Solve: (a) In the process of charging by rubbing, electrons are removed from one material and transferred into the other because they are relatively free to move. Protons, on the other hand, are tightly bound in the nuclei. So, electrons have been added to the plastic rod to make it negatively charged. (b) Because each electron has a charge of 1.60 ! 10 " 19 C , the number of electrons added is 20 ! 10 " 9 C 1.60 ! 10 " 19 C = 1.25 ! 10 11 25.6. Model: Use the charge model. Solve: (a) No, we cannot conclude that the wall is charged. Attractive electric forces occur between (i) two opposite charges, or (ii) a charge and a neutral object that is polarized by the charge. Rubbing the balloon does charge the balloon. Since the balloon is rubber, its charge is negative. As the balloon is brought near the wall, the wall becomes polarized. The positive side of the wall is closer to the balloon than the negative side, so there is a net attractive electric force between the wall and the balloon. This causes the balloon to stick to the wall, with a normal force balancing the attractive electric force and an upward frictional force balancing the very small weight of the balloon. (b) 25.14. Model: Charges A, B, and C are point charges. Visualize: Please refer to Figure Ex25.14. Charge A experiences an electric force r F B on A due to charge B and an electric force r F C on A due to charge C. The force r F B on A

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chapt 1 - PHYS 133 WEEK 1 CHAPTER 25 25.2 Model Use the...

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