Physics for Scientists and Engineers 8ed - ch30 - end of chapter questions

# Physics for Scientists and Engineers 8ed - ch30 - end of chapter questions

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Questions W denotes answer available in Student SolutionsManual/Study Guide; O denotes objective question 1. O What creates a magnetic field? Choose every correct answer. (a) a stationary object with electric charge (b) a moving object with electric charge (c) a stationary conductor carrying electric current (d) a difference in electric potential (e) an electric resistor. Note: In Chapter 34, we will see that a changing electric field also creates a magnetic field. 2. O A long, vertical, metallic wire carries downward electric current. (i) What is the direction of the magnetic field it creates at a point 2 cm horizontally east of the center of the wire? (a) north (b) south (c) east (d) west (e) up (f) down (ii) What would be the direction of the field if the current consisted of positive charges moving downward, instead of electrons moving upward? Choose from the same possibilities. 3. O Suppose you are facing a tall makeup mirror on a vertical wall. Fluorescent tubes framing the mirror carry a clockwise electric current. (i) What is the direction of the magnetic field created by that current at a point slightly to the right of the center of the mirror? (a) up (b) down (c) left (d) right (e) horizontally toward you (f) away from you (ii) What is the direction of the field the current creates at a point on the wall outside the frame to the right? Choose from the same possibilities. 4. Explain why two parallel wires carrying currents in opposite directions repel each other. 5. O In Active Figure 30.8, assume I 1 = 2 A and I 2 = 6 A. What is the relationship between the magnitude F 1 of the force exerted on wire 1 and the magnitude F 2 of the force exerted on wire 2? (a) F 1 = 6 F 2 (b) F 1 = 3 F 2 (c) F 1 = F 2 (d) F 1 = F 2 /3 (e) F 1 = F 2 /6 6. O Answer each question yes or no. (a) Is it possible for each of three stationary charged particles to exert a force of attraction on the other two? (b) Is it possible for each of three stationary charged particles to repel both of the other particles? (c) Is it possible for each of three current-carrying metal wires to attract the other two? (d) Is it possible for each of three current- carrying metal wires to repel both of the other wires? André-Marie Ampère’s experiments on electromagnetism are models of logical precision and included observation of the phenomena referred to in this question. 7. Is Ampère’s law valid for all closed paths surrounding a conductor? Why is it not useful for calculating B r for all such paths? 8. Compare Ampère’s law with the Biot–Savart law. Which is more generally useful for calculating B r for a current-carrying conductor? 9. A hollow copper tube carries a current along its length. Why = 0 B r is inside the tube? Is B r nonzero outside the tube? 10. O (i)

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Physics for Scientists and Engineers 8ed - ch30 - end of chapter questions

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