Electrostatics and Magnetostatics: Key Terms (Vocabulary)

Vocabulary flashcards covering core concepts from the lecture notes: charge, Coulomb’s law, field concepts (E and B), Ampère’s force law, Lorentz force, constants ε0 and μ0, current elements, and related ideas.

Charge

A fundamental property of matter that gives rise to electric forces; comes in positive or negative; carried by particles like electrons and protons; charge is conserved in isolated systems.

Conservation of charge

The principle that the total electric charge in an isolated system remains constant over time.

Coulomb's law

The electrostatic force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation; directed along the line joining the charges.

Permittivity of free space (ε0)

A constant describing how electric fields propagate in vacuum; ε0 ≈ 8.854×10^-12 F/m (farads per meter); appears in Coulomb’s law as the 1/(4π ε0) factor.

Coulomb's constant (k = 1/(4π ε0))

The proportionality factor in Coulomb's law that converts charge interaction to force in vacuum.

Ampère's force law (magnetostatics)

The force between current elements in steady currents; depends on I dl and I dl' and their geometry, with the force arising from magnetic interactions; valid for stationary currents.

Permeability of free space (μ0)

A constant describing the magnetic response of vacuum; μ0 = 4π×10^-7 H/m; appears in Ampère’s law for force between current elements.

Current element (I dl)

A small segment of a current-carrying conductor, where I is the current and dl is an infinitesimal length vector along the wire.

Magnetic field (B)

A field produced by moving charges (currents) that exerts force on moving charges and current elements; central to magnetic interactions.

Electric field (E)

A field representing the force per unit charge in space; exists due to charges and interacts with charges present in the field.

Lorentz force law

The force on a charge q moving with velocity v in electric and magnetic fields: F = q(E + v × B).

Field concept (electric and magnetic fields)

An approach where forces are mediated by preexisting fields (E and B) in space, rather than direct action-at-a-distance.

Action at a distance

The idea that forces can act through empty space without a mediating medium or field; historical alternative to the field viewpoint.

Direction of Coulomb force

For two charges, the force on each charge lies along the line connecting them; repulsive if charges have the same sign, attractive if opposite signs.

Directed distance vector (r)

The vector from one charge to another; r = r1 − r2; its magnitude is the separation, and its unit vector points along the line joining the charges.

Superposition principle (electrostatics/magnetostatics)

The net force (or field) from multiple sources is the vector sum of the individual forces (or fields) from each source.

Parallel currents (I1 and I2) attraction

Like currents in parallel attract each other; currents in opposite directions repel.

Cross product identity (vector triple product)

Mathematical relation used to simplify expressions like a × (b × c); can be rearranged into equivalent forms involving dot products.

Electric field due to moving charges (E and B interpretation in Lorentz viewpoint)

In Lorentz’s interpretation, a force on a test charge can be seen as arising from preexisting electric and magnetic fields (E and B) at the point of the charge.