Chapter 24 Magnetic Fields and ForcesThursday, March 11, 2010

8:26 PM

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http://electronics.howstuffworks.com/speaker5.htm

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Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-W esley.

Magnetic Fields Exert Torques on Current Loops

Slide 24-42

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CP 24 Problem 24.23 describes two particles that orbit the earth's magnetic field lines. Calculate the frequency of the circular orbit for (a) an electron with speed 1.0 × 106

m/s, and (b) a proton with speed 5.0 × 104 m/s. (The strength of the earth's magnetic field is approximately 5.0 × 10-5 T.)

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CP 26 A mass spectrometer similar to the one in Figure 24.36 is designed to separate protein fragments. The fragments are ionized by the removal of a single electron, then they enter a 0.80 T uniform magnetic field at a speed of 2.3 × 105 m/s. If a fragment has a mass that is 85 times the mass of the proton, determine the distance between the points where the ion enters and exits the magnetic field.

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enters and exits the magnetic field.

CP 45 The two 10-cm-long parallel wires in the figure are separated by 5.0 mm. For what value of the resistor R will the force between the two wires be 5.4 × 10-5 N?

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CP 47 An electron travels with a speed of 1.0 × 107 m/s between two parallel charged plates, as shown in the figure. The plates are separated by 1.0 cm and are charged by a 200 V battery. What magnetic field strength and direction will allow the electron to pass between the plates without being deflected?

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CP 56 A 1.0-m-long, 1.0-mm-diameter copper wire carries a current of 50.0 A towards the East. Suppose we create a magnetic field that produces an upward force on the wire exactly equal in magnitude to the wire's weight, causing the wire to "levitate." What are the magnetic field's magnitude and direction?

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