Electric Potential (Physics)

Recall cards on electric potential energy, electric potential, and their applications. Electric potential energy: that the Coulomb force is conservative and path-independent, the symbol U and its joule unit, W = -delta U, the zero reference at infinity, the two-charge result U = k*q*Q/r, Coulomb's constant, and the zero closed-loop line integral. Electric potential and potential difference: V = U/q, the symbol V, test-charge independence, the volt as J/C, delta V = delta U/q, V_B - V_A, voltage, delta U = q*delta V, E = -delta V/delta s in a uniform field, 1 N/C = 1 V/m, and the electron-volt. Calculations of potential: V = k*q/r for a point charge, the 1/r versus 1/r^2 falloff, the scalar nature and algebraic superposition of potential, the electric dipole and its moment p = q*d, the integral form for a continuous distribution, and the far-field dipole potential. Field from potential: E = -dV/ds, the steepest-descent direction, E = -grad V, the partial-derivative components, and the scalar-first method. Equipotential surfaces and conductors: the definition and lines, perpendicularity to field lines, zero work along a surface, a conductor as an equipotential, grounding, and charge concentration at small radii of curvature. Applications: the Van de Graaff generator, xerography and the photoconductor, laser and ink-jet printers, and the electrostatic precipitator.