Module 8–9 Electricity and Magnetism Vocabulary Review

A comprehensive set of key vocabulary terms and concise definitions covering electric charge, fields, circuits, power, magnetism, and electromagnetic induction for Modules 8 and 9.

Electric Charge

A property of matter that can be positive or negative and causes electrical interactions; measured in coulombs (C).

Proton

Positively charged sub-atomic particle with charge +1.602 × 10⁻¹⁹ C.

Electron

Negatively charged sub-atomic particle with charge −1.602 × 10⁻¹⁹ C.

Coulomb’s Law

The electric force between two point charges is F = k·q₁·q₂ / d²; force is proportional to charge and inversely proportional to distance squared.

Coulomb’s Constant (k)

Proportionality constant in Coulomb’s law: 9 × 10⁹ N·m²/C².

Electric Field (E)

Region of force per unit charge around a charged object; E = F / q.

Electric Potential (Voltage)

Electric potential energy per unit charge; measured in volts (V).

Electric Potential Energy

Energy a charge possesses due to its position in an electric field; measured in joules (J).

Current (I)

Rate of charge flow; measured in amperes (A).

Resistance (R)

Opposition a material offers to current flow; measured in ohms (Ω).

Ohm’s Law

Relationship V = I·R; current is directly proportional to voltage and inversely proportional to resistance.

Resistivity

Intrinsic property of a material that determines its resistance per unit length and area.

Series Resistance

Equivalent resistance of resistors in series: R_total = R₁ + R₂ + ….

Parallel Resistance

Equivalent resistance of resistors in parallel: 1/R_total = 1/R₁ + 1/R₂ + ….

Electric Power (P)

Rate of electrical energy transfer; P = I·V; measured in watts (W).

Watt

Unit of power equal to one joule per second or one ampere-volt.

Generator

Device that produces electric current by rotating a coil in a magnetic field (electromagnetic induction).

Magnetic Field

Region around a magnet or moving charge where magnetic forces are exerted; lines run from north to south outside the magnet.

Magnetic Poles

Regions where a magnet’s magnetic field is strongest; always occur in north–south pairs.

Magnetic Force on a Current

Sideways force on a wire carrying current in a magnetic field; maximized when current is perpendicular to field lines.

Electromagnetic Induction

Process of inducing voltage by changing magnetic field through a loop; basis of generators and transformers.

Faraday’s Law

Induced voltage in a coil is proportional to number of turns times the rate of change of magnetic flux.

Maxwell’s Counterpart to Faraday’s Law

A changing electric field induces a magnetic field.

Transformer

Device that transfers electric power between coils via induction; changes voltage according to turns ratio.

Turns Ratio

Relationship Vs / Vp = Ns / Np; determines step-up or step-down transformer action.

Direct Current (DC)

Electric current flowing in one constant direction.

Alternating Current (AC)

Current that periodically reverses direction; U.S. mains frequency is 60 Hz.

Ampere (A)

Unit of current equal to one coulomb per second.

Ohm (Ω)

Unit of resistance; one volt per ampere.

Volt (V)

Unit of electric potential; one joule per coulomb.

Superconductor

Material with zero electrical resistance below a critical temperature.

Drift Speed

Average velocity of electrons through a conductor, typically less than 1 cm/s.

Induced Voltage

Voltage generated in a conductor when magnetic flux through it changes.

Step-Up Transformer

Transformer that increases voltage and decreases current in the secondary coil.

Step-Down Transformer

Transformer that decreases voltage and increases current in the secondary coil.

Hertz (Hz)

Unit of frequency; one cycle per second, used to describe AC vibration rate.

Electric Field Intensity Formula

E = k·q / d² for a point charge, where q is source charge and d is distance.

Power Company Supply

Provides energy to move electrons through household circuits, not the electrons themselves.

Magnetic Induction in Loops

Magnetic field strength inside a loop is greater than around a straight wire because field contributions add.

Inverse-Square Law

Principle that certain forces (electric, magnetic) decrease in proportion to 1/d² from the source.