Theory
Any charged particle in an electric field will feel a force proportional to the charge and field strength such that, where F is force, q is charge, and E is electric field. Similarly, any particle moving in a magnetic field will feel a force proportional to the velocity and charge of the particle. The force felt by any particle is then equal to, where F is force, q is the charge on the particle, v is the velocity of the particle, B is the strength of the magnetic field, and is the cross product. In the case of a velocity selector, the magnetic field is always at 90 degrees to the velocity and the force is simplified to in the direction described by the cross product.
Setting the two forces to equal magnitude in opposite directions it can be shown that . Which means that any combination of electric and magnetic fields will allow charged particles with only velocity through.
Read more about this topic: Velocity Selector
Famous quotes containing the word theory:
“There could be no fairer destiny for any physical theory than that it should point the way to a more comprehensive theory in which it lives on as a limiting case.”
—Albert Einstein (1879–1955)
“Could Shakespeare give a theory of Shakespeare?”
—Ralph Waldo Emerson (1803–1882)
“Everything to which we concede existence is a posit from the standpoint of a description of the theory-building process, and simultaneously real from the standpoint of the theory that is being built. Nor let us look down on the standpoint of the theory as make-believe; for we can never do better than occupy the standpoint of some theory or other, the best we can muster at the time.”
—Willard Van Orman Quine (b. 1908)