Physics Grade 9: Electric Fields and Current Review

Comprehensive vocabulary flashcards covering electric fields, uniform fields, conductors, current density, and series/parallel circuits based on Grade 9 Physics lessons by Badr Eid.

Electric Field

The electric force per unit test charge.

Vector Field

A field that indicates both magnitude and direction at every point, such as wind velocity maps.

Scalar Field

A field where only a number is assigned to each point in space, such as temperature maps.

Test Charge

A very small positive charge used to measure the electric field without affecting the original charge distribution.

Electric Field Magnitude (Point Charge)

Calculated using the equation $E = \frac{k|q|}{r^2}$.

Principle of Superposition

The method used to calculate the net electric field at a point resulting from multiple charges.

Field Lines

Lines that begin on positive charges and end on negative charges (or at infinity) to indicate the strength and direction of the field.

Electrostatic Equilibrium

A state where the electric field at the surface of a conductor is perpendicular to the surface.

Curvature

Regions on a conductor where excess charge concentrates most; electric fields are strongest at points with large amounts of this property.

Uniform Field

An electric field in which the magnitude and direction are the same at all points.

Capacitor

A device used to store electrical energy, often consisting of two parallel metal plates.

Force on a Charge ($F$)

Calculated in a uniform field as $F = \text{Charge} \times \text{Electric Field}$.

Constant Acceleration

The type of motion experienced by a charged particle between two parallel plates because the electric field is uniform.

Conductor

A material that allows electric charges to move easily through it, such as copper or silver.

Insulator

A material in which electrons cannot move easily, such as glass, rubber, or wood.

Electric Current

The movement of electrons (or flow of charge through a wire) per unit time.

Delocalized Electrons

Electrons in metals that are not tied to a single atom and are free to move throughout the material.

Ions

Charged particles formed when materials like salt dissolve in water, allowing for electrical conduction.

Metallic Bonds

The attraction between metal cations and freely moving electrons.

Cold Welding

A process in space where two clean metal surfaces bond together without heat due to the absence of oxide layers.

Ductility

The property of metals that allows them to be stretched into wires.

Ampere

The SI unit of electric current.

Drift Velocity

The average speed of electrons moving through a conductor when an electric field is applied.

Collisions

Events occurring between moving electrons and metal ions that limit drift velocity and produce resistance.

Resistance ($R$)

The opposition to the flow of electric current in a material, measured using the equation $R = \frac{\rho L}{A}$.

Resistivity ($\rho$)

An intensive property that depends on the type of material rather than its size or shape.

Current Density ($J$)

The amount of electric current flowing through a given cross-sectional area.

Ohm's Law (Vector Form)

The relationship describing how the electric field is proportional to the current density.

Series Circuit

A circuit where resistors are connected one after another, creating a single path for current.

Parallel Circuit

A circuit that provides multiple paths for current, reducing the equivalent resistance.

Equivalent Resistance

The total resistance of a circuit; in series it is the sum ($R_1 + R_2 + ...$), while in parallel it is less than the smallest individual resistor.

Alternating Current (AC)

A type of current where electrons reverse their direction periodically.

Surge Protector

A device that protects electronics by decreasing its own resistance to divert current during a power surge.