Electric Charges and Fields (Physics)

Recall cards on electric charge and the electric field. Electric charge: its two types, like-repels-unlike-attracts, the coulomb unit, the elementary charge e = 1.602 x 10^-19 C, quantization, conservation, and the charged constituents of the atom, plus what makes an ion positive or negative. Conductors and insulators: conduction electrons and free charge flow, why excess charge spreads on a conductor, why charge stays put on an insulator, polarization, why a charged object attracts a neutral one, charging by induction, and grounding. Coulomb's law: F = k q1 q2 / r^2, its proportionalities, the permittivity of free space epsilon_0 = 8.85 x 10^-12, Coulomb's constant k = 8.99 x 10^9, the line of action, Newton's third law, and superposition. The electric field: E as force per unit positive charge with F = QE, the newton-per-coulomb unit, the field of a point charge, its direction, its independence from the test charge, and superposition. Continuous charge distributions: linear, surface, and volume charge densities, field by integration, and the uniform field sigma / (2 epsilon_0) of an infinite charged plane. Electric field lines: tangency, where they begin and end, line density and count, why they never cross, and that they are only a visualization. Electric dipoles: the definition, the dipole moment p = q d, the coulomb-meter unit, the zero net force and the torque tau = p x E in a uniform field, the alignment tendency, and permanent versus induced dipoles.