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Figure 32.26 shows the apparatus used in a lecture demonstration of paramagnetism and diamagnetism. A sample of the magnetic material is suspended by a string ( L= 2 m) in a region (d=2 cm) between the two poles of a powerful electromagnet. Pole P1 is sharply pointed and pole P2 is rounded as indicated. Any deflection of the string from the vertical is visible to the audience by means of an optical projection system (not shown). (a) First, a bismuth (highly diamagnetic) sample is used. When the electromagnet is turned on, the sample is observed to deflect slightly (about 1 mm ) toward one of the poles. What is the direction of this deflection? (Hint: Note the way the wire is wound.) (b) Next, an aluminum (paramagnetic, conducting) sample is used. The sample deflects strongly (about 1 cm ) toward one pole for about a second and then deflects moderately (a few millimeters) toward the other pole. Explain and indicate the direction of these deflections. (Hint: Note that the aluminum sample is a conductor.) (c) What would happen if a ferromagnetic sample were used?
A 10.0−kg block of metal is suspended from a scale and immersed in water, as in Figure P9.30. The dimensions of the block are 12.0 cm×10.0 cm×10.0 cm. The 12.0−cm dimension is vertical, and the top of the block is 5.00 cm below the surface of the water. (a) What are the forces exerted by the water on the top and bottom of the block? (Take P0=1.0130×105 N/m2.)