Introduction to Electrostatics: Electric Force and Field

Explore electric charge, its positive and negative types, and how rubbing creates attraction or repulsion. Learn the coulomb unit and the electron charge, including 1.6×10^-19 C per electron.

Explore insulators and conductors, where charge exists in discrete multiples of e and is conserved; insulators localize charge while conductors distribute it on surfaces, via rubbing or direct contact.

Charge a conductor by induction using grounding and remnant electron flow. Explore polarization by induction in conductors and insulators, showing how neutral objects are attracted.

Explore Coulomb's law, deriving the electrostatic force between point charges with the Coulomb constant, and learn how charge sign, distance, and Newton's third law govern attraction, repulsion, and potential energy.

Apply Coulomb's law to the Bohr model of the hydrogen atom, equate electric to centripetal force, find electron speed, and compare electric and gravitational forces to show gravity is negligible.

Apply superposition of electric forces to compute net forces via vector sums using Coulomb's law, solving three examples, including an equilateral triangle, yielding 0.87 N at 30 degrees.

Polarization by induction occurs when an external charge shifts electrons. This creates a negative side near the charge and a positive side away, explained by Coulomb’s law 1/r^2 and superposition.

Explore the electric field as a non-contact force from a source charge on test charges, with E = F/q and direction determined by charge sign.

Explore the electric field from a point charge, its inverse-square magnitude, and how direction depends on charge sign, using unit vectors to show away from positives and toward negatives.

Explore the superposition of electric fields in electrostatics by summing vector contributions from multiple charges to determine the net field at a point, with practical square-charge examples.

Visualize electric field lines that point along the field, densify with stronger magnitude, originate from positive charges and end at negative charges, and never cross, illustrating uniform and non-uniform fields.

Explore the motion of an electron in a uniform electric field between parallel plates, compute the field strength, exit speed, and compare with a proton’s displacement using kinematics.

Explore how electric fields arise from point charges and extended charge distributions, using superposition, delta q, and calculus to derive the field for line, area, and volume charges.

Explore line charge distribution using a variable line density that varies with x, integrating to find the electric field at point P, with a symmetric line from -L to L.

Compute the net electric field from a line charge of density lambda at point p above the rod's left end by integrating the x and y components.

Derive the on-axis electric field of a uniformly charged ring of radius r and charge q at distance x from the center using symmetry.

Compute the electric field from a charged area by integrating small surface elements, deriving the disk field and its infinite-plane limit using surface charge density and the Coulomb constant.

Explore deriving the electric field from charged line, area, and volume using volume charge density (total charge per unit volume). Compute net field via volume elements and integrals.

Explain electric flux as the scalar measure of field lines passing through a surface, using E·A and the angle theta, and illustrate surface orientation with a cube and a hemisphere.

Explore how a point charge produces a constant electric flux through a spherical surface, equal to q/ε0 and independent of surface size or shape.

Apply Gauss's law to relate electric flux through a closed surface to the total enclosed charge, using superposition to sum electric fields from multiple point charges via E·dA.

Explore planar, cylindrical, and spherical symmetry to compute electric fields with Gauss's law. Apply Gaussian surfaces to line charges, infinite planes, parallel plates, and solid spheres to derive field expressions.

Explore four properties of conductors in electrostatic equilibrium: zero interior field, surface charges only, perpendicular surface field, and nonuniform surface charge density.

Apply Gauss's law to a conducting spherical shell with a central charge, showing the field inside the conductor is zero and the outside field corresponds to net enclosed charge -2Q.

Learn how a hollow conductor creates a Faraday cage, yielding zero electric field inside the cavity when no net charge resides there; see it in the microwave and elevator shielding.

Celebrate finishing the introductory electrostatics module and explore the complete electricity and magnetism course for deeper learning, with reviews and instructor resources.