Chapter 15 Electric Forces and Electric Fields Quick Quizzes 1.(b). Object A must have a net charge because two neutral objects do not attract each other. Since object A is attracted to positively-charged object B, the net charge on A must be negative. 2.(b). By Newton’s third law, the two objects will exert forces having equal magnitudes but opposite directions on each other. 3.(c). The electric field at point Pis due to charges otherthan the test charge. Thus, it is unchanged when the test charge is altered. However, the direction of the force this field exerts on the test change is reversed when the sign of the test charge is changed. 4.(a). If a test charge is at the center of the ring, the force exerted on the test charge by charge on any small segment of the ring will be balanced by the force exerted by charge on the diametrically opposite segment of the ring. The net force on the test charge, and hence the electric field at this location, must then be zero.
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