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71.

71. II The 10-turn loop of wire shown in FIGURE P29.71 lies in a horizontal plane, parallel to a uniform horizontal magnetic field, and carries a 2.0 A current. The loop is free to rotate about a nonmagnetic axle through the center. A 50 g mass hangs from one edge of the loop. What magnetic field strength will prevent the loop from rotating about the axle? 10 turns 5.0 cm 10.0 cm 20 cm 50 g B = 0.5 T Axle FIGURE P29.71 FIGURE P29.7281. III A flat, circular disk of radius R is uniformly charged with (MC total charge Q. The disk spins at angular velocity as about an axis through its center. What is the magnetic field strength at the center of the disk? 83. "I An innitely wide flat sheet of charge flows out of the page in FIGURE CP29.83. The current per unit width along the sheet (amps per meter) is given by the linear current density J3. a. What is the shape of the magnetic eld? To answer this question, you may find it helpful to approximate the current sheet as many parallel, closely spaced current-carrying wires. Give your answer as a picture showing magnetic field vectors. b. Find the magnetic eld strength at distance d above or below the current sheet. Extends tom Extends ton: FIGURE C?29.83 Linear current density J