20_InstSolManual_PDF_Part17

20_InstSolManual_PDF_Part17 - nitude of the field. 20.58....

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Figure 20.54b shows the magnetic fields at the wires for the case where one current is to the left and the other is to the right. The directions of the forces on the wires exerted by these fields are also shown. The wires repel. 20.55. Set Up: Measurements on a typical extension cord give that the centers of the two wires are separated by about 4 mm. Solve: Since the currents are in opposite directions the wires repel. 20.56. Set Up: Solve: The force is proportional to each current. 20.57. Set Up: At the center of a circular loop The direction of can be found by the right-hand rule: with the thumb of your right hand in the direction of the current your fingers curl around the wire in the direction of the magnetic field. Solve: (a) (b) The plane of the loop should be perpendicular to the earth’s field and the current should be directed as shown in Figure 20.57. Figure 20.57 Reflect: A large current is required. Note that only applies at the center of the circular loop. The current produces magnetic field at other points but only at the center of the loop do we have a simple expression for the mag-
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Unformatted text preview: nitude of the field. 20.58. Set Up: The magnetic field at the center of N circular loops is Solve: 20.59. Set Up: The magnetic field at the center of N circular loops is Solve: Therefore, 24 turns are required. 20.60. Set Up: Solve: I 5 2 RB m 5 2 1 8 3 10 2 2 m 21 3.0 3 10 2 12 T 2 4 p 3 10 2 7 T # m / A 5 3.8 3 10 2 7 A. 1 gauss 5 1 3 10 2 4 T. R 5 8 cm. B 5 m I 2 R . N 5 2 RB m I 5 2 1 6.00 3 10 2 2 m 21 6.39 3 10 2 4 T 2 1 4 p 3 10 2 7 T # m / A 21 2.50 A 2 5 24.4 B 5 N m I 2 R . B 5 1 4 p 3 10 2 7 T # m / A 21 600 21 0.500 A 2 2 1 2.00 3 10 2 2 m 2 5 9.42 3 10 2 3 T B 5 N m I 2 R . B 5 m I 2 R B earth I I I 5 2 RB m 5 2 1 0.11 m 21 0.50 3 10 2 4 T 2 4 p 3 10 2 7 T # m / A 5 8.8 A. B S 4 p 3 10 2 7 T # m / A. B 5 m I 2 R . F new 5 m l 1 3 I 1 21 2 I 2 2 2 p r 5 6 m lI 1 I 2 2 p r 5 6 F . F 5 m lI 1 I 2 2 p r . F 5 1 4 p 3 10 2 7 N / A 2 21 2.0 m 21 5.0 A 2 2 2 p 1 4.0 3 10 2 3 m 2 5 2.5 3 10 2 3 N. 4 p 3 10 2 7 N / A 2 . F 5 m lII r 2 p r . Magnetic Field and Magnetic Forces 20-17...
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