20_InstSolManual_PDF_Part23 - that equals the weight mg of...

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20.81. Set Up: Use to calculate With downward, and The direction of the force is given by the right-hand rule and the magnitude is given by The charge of the ball is Solve: The directions of and are shown in Figure 20.81, where the downward direction is into the page. The right-hand rule (rhr) direction is north, but since the charge is negative the force is opposite the rhr direction and is to the south. At the bottom of the shaft the speed of the ball is so Figure 20.81 Reflect: The magnetic force is much less than the gravity force on the ball. 20.82. Set Up: The magnetic force must be upward and equal to mg. The direction of is determined by the direction of I in the circuit. with where V is the battery voltage. Solve: (a) The forces are shown in Figure 20.82. The current I in the bar must be to the right to produce upward. To produce current in this direction, point a must be the positive terminal of the battery. Figure 20.82 (b) 20.83. Set Up: The maximum current I is the current that results in an upward magnetic force that equals the
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Unformatted text preview: that equals the weight mg of the bar. with Solve: Reflect: The current required to lift the bar is quite large, about 33 A. For a bar of less mass, less current would be required to lift the bar off the supports and break the circuit. V 5 mgR lB 5 1 0.750 kg 21 9.80 m / s 2 21 25.0 V 2 1 0.500 m 21 0.450 T 2 5 817 V. VlB R 5 mg . IlB 5 mg . F B 5 mg . f 5 90°. F 5 IlB sin f , I 5 V R . F B m 5 IlB g 5 VlB Rg 5 1 175 V 21 0.600 m 21 1.50 T 2 1 5.00 V 21 9.80 m / s 2 2 5 3.21 kg. IlB 5 mg . F B 5 mg . I B F B mg F S B I 5 V R , f 5 90°. F B 5 IlB sin f , F S B F S B N S E W B v F rhr direction F 5 q v B 5 1 6.40 3 10 2 11 C 21 49.5 m / s 21 0.250 T 2 5 7.92 3 10 2 10 N. f 5 90°, q 5 1 4.00 3 10 8 21 1.60 3 10 2 19 C 2 5 6.40 3 10 2 11 C. v 5 " 2 g 1 125 m 2 5 " 2 1 9.80 m / s 2 21 125 m 2 5 49.5 m / s. B S v S 2 1 4.00 3 10 8 2 e . F 5 q v B sin f . y 5 125 m. a y 5 1 9.80 m / s 2 v y 5 0, 1 y v y . v y 2 5 v y 2 1 2 a y y Magnetic Field and Magnetic Forces 20-23...
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