Introduction to electromagnetism is a quantity used to determine how a particle will behave in an electric field. There are three possible "types" of charge: positive, negative, and neutral. However, the distinction between positive and negative is by convention only. Electric charge is quantized in units of the elementary charge, formula_1, where a proton has a charge of formula_2 and an electron has a charge of formula_3. The SI unit of charge is the coulomb. The elementary charge formula_1 was first measured by Robert Millikan in his oil drop experiment in which the electric force on the particle is set to exactly counter
Particle in a box not strictly hold for the measured momentum ; the energy eigenstate formula_38 is not a momentum eigenstate, and, in fact, not even a superposition of two momentum eigenstates, as one might be tempted to imagine from equation () above: peculiarly, it has no well-defined momentum before measurement! In classical physics, the particle can be detected anywhere in the box with equal probability. In quantum mechanics, however, the probability density for finding a particle at a given position is derived from the wavefunction as formula_39 For the particle in a box, the probability density for finding the particle at a given