Resolução tipler vol. 2 fisica

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Chapter 21 The Electric Field 1: Discrete Charge Distributions
Conceptual Problems
*1 •• Similarities: The force between charges and masses varies as 1/r2. The force is directly proportional to the product of the charges or masses.

Differences: There are positive and negative charges but only positive masses. Like charges repel; like masses attract.

The gravitational constant G is many orders of magnitude smaller than the Coulomb constant k. 2 • Determine the Concept No. In order to charge a body by induction, it must have charges that are free to move about on the body. An insulator does not have such charges. 3 •• Determine the Concept During this sequence of events, negative charges are attracted from ground to the rectangular metal plate B. When S is opened, these charges are trapped on B and remain there when the charged body is removed. Hence B is negatively charged and (c) is correct. 4 •• (a) Connect the metal sphere to ground; bring the insulating rod near the metal sphere and disconnect the sphere from ground; then remove the insulating rod. The sphere will be negatively charged. (b) Bring the insulating rod in contact with the metal sphere; some of the positive charge on the rod will be transferred to the metal sphere. (c) Yes. First charge one metal sphere negatively by induction as in (a). Then use that negatively charged sphere to charge the second metal sphere positively by induction.

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Chapter 21

*5 •• Determine the Concept Because the spheres are conductors, there are free electrons on them that will reposition themselves when the positively charged rod is brought nearby. (a) On the sphere near the positively charged rod, the induced charge is negative and near the rod. On the other sphere, the net charge is positive and on the side far from the rod. This is shown in the diagram. (b) When the spheres are separated and far apart and the rod has been removed, the induced charges are