Unformatted text preview: 20.10. Set Up: Eq. (20.3) relates v , B and E for a velocity selector. For the ions to pass through undeflected, the net force must be zero and therefore the electric and magnetic forces must be in opposite directions. For positive charges the electric force is in the same direction as the electric field and for negative charges the field and force are in opposite directions. Solve: (a) (b) Take the velocity to be to the right and let the electric field be downward, as shown in Figure 20.10. Since the charge is positive, the electric force is downward. For an ion to pass through undeflected, the net force must be zero, so the magnetic force must be upward. Using the right-hand rule for and we deduce that must be directed into the plane of the figure. Figure 20.10 (c) For a negative charge and the and fields of Figure 20.10, the direction of each force is reversed. But they are still in opposite directions from each other, so will cancel if their magnitudes are the same. The magnitude of thestill in opposite directions from each other, so will cancel if their magnitudes are the same....
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- Spring '07
- Force, Electric charge, opposite directions, Magnetic Field and Magnetic Forces, 3.25 3 103 m, 4.50 3 1022 m, 5 1 8.75 3 103 m