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Physics for Scientists and Engineers 8ed - ch31 - end of chapter questions

Physics for Scientists and Engineers 8ed - ch31 - end of chapter questions

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Questions W denotes answer available in Student SolutionsManual/Study Guide; O denotes objective question 1. What is the difference between magnetic flux and magnetic field? 2. O Figure Q31.2 is a graph of the magnetic flux through a certain coil of wire as a function of time, during an interval while the radius of the coil is increased, the coil is rotated through 1.5 revolutions, and the external source of the magnetic field is turned off, in that order. Rank the electromotive force induced in the coil at the instants marked A through F from the largest positive value to the largest magnitude negative value. In your ranking, note any cases of equality and also any instants when the emf is zero. 3. O A flat coil of wire is placed in a uniform magnetic field that is in the y direction. (i) The magnetic flux through the coil is a maximum if the coil is (a) in the xy plane (b) in either the xy or the yz plane (c) in the xz plane (d) in any orientation, because it is a constant (ii) For what orientation is the flux zero? Choose the best answer from the same possibilities. 4. O A square, flat coil of wire is pulled at constant velocity through a region of uniform magnetic field directed perpendicular to the plane of the coil as shown in Figure Q31.4. (i) Is current induced in the coil? (a) yes, clockwise (b) yes, counterclockwise (c) no (ii) Does charge separation occur in the coil? (a) yes, with the top positive (b) yes, with the top negative (c) no 5. The bar in Figure Q31.5 moves on rails to the right with a velocity v r and the uniform, constant magnetic field is directed out of the page. Why is the induced current clockwise? If the bar were moving to the left, what would be the direction of the induced current? 6. O (i) As the square coil of wire in Figure Q31.4 moves perpendicular to the field, is an external force required to keep it moving with constant speed? (ii) Answer the same question for the bar in Figure Q31.5. (iii) Answer the same question for the bar in Figure Q31.6. 7. In a hydroelectric dam, how is energy produced that is then transferred out by electrical transmission? That is, how is the energy of motion of the water converted to energy that is transmitted by AC electricity? 8. A piece of aluminum is dropped vertically downward between the poles of an electromagnet. Does the magnetic field affect the velocity of the aluminum? 9. O What happens to the amplitude of the induced emf when the rate of rotation of a generator coil is doubled? (a) It becomes 4 times larger. (b) It becomes 2 times larger. (c) It is unchanged. (d) It becomes 1/2 as large. (e) It becomes 1/4 as large. 10. When the switch in Figure Q31.10a is closed, a current is set up in the coil and the metal ring springs upward (Fig. Q31.10b). Explain this behavior. 11.

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Physics for Scientists and Engineers 8ed - ch31 - end of chapter questions

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