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Electric charge is a conserved property of matter. Opposite charges attract, like charges repel, and the force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them. This relationship is described by Coulomb's law.

An electric field represents the force that a positive test charge would experience at a point in space. Field lines begin on positive charges and terminate on negative charges. The density of field lines indicates the relative strength of the electric field.

Electric potential energy changes when a charge moves through an electric field. Electric potential, measured in volts, is potential energy per unit charge. A battery creates a potential difference that can drive current through a closed circuit.

Current is the rate of flow of electric charge. Resistance measures how strongly a material opposes current. Ohm's law states that voltage equals current multiplied by resistance. In series circuits, resistances add directly. In parallel circuits, the reciprocal of the equivalent resistance equals the sum of the reciprocals of each branch resistance.

Magnetic fields are produced by moving charges and by changing electric fields. A current-carrying wire generates circular magnetic field lines around the wire. The right-hand rule gives the direction of the magnetic field. A charged particle moving through a magnetic field experiences a force perpendicular to both its velocity and the field.

Electromagnetic induction occurs when a changing magnetic flux produces an electromotive force. Faraday's law relates induced voltage to the rate of change of magnetic flux. Lenz's law states that the induced current opposes the change that created it.

Likely student gaps: 1. Distinguishing electric field from electric potential. 2. Understanding why equivalent resistance decreases in parallel circuits. 3. Applying the right-hand rule consistently. 4. Connecting magnetic flux changes to induced current direction.