21.25. Set Up: Use Lenz’s law to determine the direction of the induced current. The force required to maintain constant speed is equal and opposite to the force that the magnetic field exerts on the rod because of the current in the rod. Solve: (a) (b) is into the page. The flux increases as the bar moves to the right, so the magnetic field of the induced current is out of the page inside the circuit. To produce magnetic field in this direction the induced current must be counter-clockwise, so from b to a in the rod. (c) is to the left. To keep the bar moving to the right at constant speed an external force with magnitude and directed to the right must be applied to the bar. Reflect: The force on the rod due to the induced current is directed to oppose the motion of the rod. This agrees with Lenz’s law. 21.26. Set Up and Solve: (a) Each slab of flowing blood has maximum width d and is moving perpendicular to the field with speed v . becomes (b) (c) The blood vessel has cross sectional area
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This note was uploaded on 03/06/2009 for the course PHYS 114 taught by Professor Shoberg during the Spring '07 term at Pittsburg State Uiversity.