Section 3: Electricity and Magnetism

Electric Charge

A property of matter that causes electric forces; can be positive or negative, carried by particles such as electrons and protons.

Electric Current

The flow of electric charge through a conductor, usually carried by electrons, and measured in amperes (A).

Voltage

The potential difference that provides energy for electric charges to flow through a circuit; measured in volts (V).

Resistance

A property of a material that opposes the flow of electric current; measured in ohms (Ω).

Ohm’s Law

A relationship stating that voltage equals current multiplied by resistance (V = IR).

Conductor

A material that allows electric charges to flow easily, such as metals like copper.

Insulator

A material that resists the flow of electric charge because electrons are tightly bound.

Direct Current (DC)

Electric current that flows in one direction only, such as the current from a battery.

Alternating Current (AC)

Electric current that periodically changes direction, such as the current from wall outlets.

Circuit Types

Series circuits have components connected in a single path, while parallel circuits have components connected in multiple paths.

Equivalent Resistance

The total resistance of a circuit that can replace multiple resistors with one.

Closed Circuit

A complete loop that allows electric current to flow.

Open Circuit

A broken or incomplete path that prevents current from flowing.

Capacitor

A device that stores electrical energy in an electric field.

Inductor

A coil of wire that stores energy in a magnetic field and opposes changes in current.

Electric Field

A region around a charged object where other charges experience an electric force.

Electric Field Strength

The force experienced by a positive test charge divided by the magnitude of that charge.

Electric Potential

Electric potential energy per unit charge.

Electric Potential Difference

The difference in electric potential between two points that drives charge flow.

Coulomb’s Law

The electrostatic force between two charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

Like Charges

Charges with the same sign that repel each other.

Opposite Charges

Charges with different signs that attract each other.

Grounding

The process of safely transferring excess charge to Earth by providing a path for charge to flow away.

Static Electricity

The buildup of electric charge on an object, often caused by friction.

Charging by Contact

Charging an object by touching it with a charged object, allowing electrons to transfer.

Charging by Induction

Charging an object without direct contact by bringing a charged object nearby, which rearranges internal charges.

Faraday Cage Effect

The phenomenon that keeps people safe inside a car during lightning because charge stays on the outside.

Neural Action Potential

A rapid change in electric potential across a neuron’s membrane that transmits signals.

Electric Potential Energy

The energy a charged object has due to its position in an electric field.

Scalar Quantity

A quantity with magnitude only, such as voltage.

Vector Quantity

A quantity with both magnitude and direction, such as electric field strength.

Resistor

A circuit component designed to provide a specific amount of resistance and limit current flow.

Electrostatic Equilibrium

A state where charges in a conductor are not moving and the electric field inside the conductor is zero.

Electric Field Lines

Imaginary lines that represent the direction and strength of an electric field.

Cell Membrane Electric Fields

Electric fields across cell membranes that allow nerve signaling.

Charge Distribution on Conductors

In electrostatic equilibrium, excess charge resides on the surface of a conductor.

Voltage in Series Circuit

Divided among the components and adds up to the total voltage supplied.

Voltage in Parallel Circuit

The same across all components connected in parallel.

Current in Series Circuit

The same through all components.

Current in Parallel Circuit

Divides among different branches and adds up to the total current.

Effect of Length on Resistance

Increasing the length of a wire increases resistance.

Effect of Cross-Sectional Area on Resistance

Increasing the cross-sectional area decreases resistance.

Capacitance

A measure of how much electric charge a capacitor can store.

Back Electromotive Force (Back-EMF)

A voltage produced by an inductor that resists changes in current.

RL Circuit

A circuit that contains resistors and inductors and causes current to change gradually.

Main Function of a Resistor

To limit current and protect circuit components.

Main Function of a Capacitor

To store and release electrical energy and smooth voltage changes.

Main Function of an Inductor

To resist changes in current and store energy in a magnetic field.

Electrostatic Force

The attractive or repulsive force between charged objects.

Impulse

The change in momentum caused by a force applied over a period of time.

Electric Fish

Animals that generate electric fields to navigate and communicate.

Battery

A device that converts chemical energy into electrical energy by creating a potential difference.

Defibrillators

Medical devices that use high electric potential differences to restore heart rhythm.

Lightning

A large electrical discharge caused by charge buildup between clouds and the ground.

Solar Panels

Devices that use electric fields to direct electron flow and generate electricity.

Electrophoresis

The use of electric fields to separate DNA or proteins by charge and size.