Glossary
Capacitance
The ability of a component to store an electric charge, defined as the ratio of the charge stored to the potential difference across the component.
Example:
A large capacitance means a capacitor can store a significant amount of charge at a given voltage.
Capacitors
Passive electrical components that store electrical energy in an electric field between two conductive plates separated by a dielectric material.
Example:
The flash in a camera uses a capacitor to quickly release a burst of stored energy to power the light.
Charged particles
Subatomic particles, such as electrons and protons, that possess an intrinsic electric charge, leading to electric forces.
Example:
When you rub a balloon on your hair, electrons (negative charged particles) transfer from your hair to the balloon, giving it a net negative charge.
Circuit Components
Individual electrical devices, such as resistors, capacitors, and inductors, that perform specific functions within an electric circuit.
Example:
The motherboard of a computer is densely packed with various circuit components that process and store information.
Conduction (charge distribution)
A method of charging an object by direct contact with a charged object, allowing electrons to flow and distribute evenly.
Example:
Touching a charged metal sphere with an uncharged metal sphere will transfer charge by conduction, making both spheres charged.
Conservation of Electric Charge
A fundamental principle stating that the total electric charge in an isolated system remains constant; charge cannot be created or destroyed, only transferred.
Example:
When a glass rod is rubbed with silk, electrons are transferred, but the total charge of the rod-silk system remains constant, illustrating the conservation of electric charge.
Conservation of Electric Energy
The principle that the total electric energy within a closed system remains constant, though it can be transformed from one form to another.
Example:
In a simple circuit, the chemical energy from a battery is converted into electrical energy, which then transforms into light and heat in a bulb, demonstrating the conservation of electric energy.
Conservative Forces
Forces for which the work done in moving an object between two points is independent of the path taken, and the total mechanical energy is conserved.
Example:
Gravity is a conservative force because the work done lifting an object depends only on the initial and final heights, not the path.
Contour Maps
Maps that use isolines to represent a three-dimensional surface or field on a two-dimensional plane, often used for elevation or potential.
Example:
Geologists use contour maps to visualize the shape of mountains and valleys.
Coulomb's Law
A fundamental law stating that the electric force between two point charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.
Example:
Using Coulomb's Law, you can calculate the strong repulsive force between two protons when they are very close together.
Coulombs (C)
The SI unit of electric charge, defined as the amount of charge transported by a constant current of one ampere in one second.
Example:
A typical lightning bolt can transfer several coulombs of charge between the cloud and the ground.
Electric Charge
A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field, existing as positive or negative.
Example:
An electron carries a fundamental negative electric charge.
Electric Current
The flow of electric charge through a conductor, typically driven by voltage and measured in Amperes.
Example:
When you flip a light switch, an electric current flows through the wires to illuminate the bulb.
Electric Forces
The fundamental interactions between electrically charged particles, which can be attractive (opposite charges) or repulsive (like charges).
Example:
The attraction between a positively charged proton and a negatively charged electron in an atom is due to electric forces.
Electric Permittivity (Dielectric Constant)
A measure of how an electric field affects, and is affected by, a dielectric medium, indicating how easily a material can store electrical energy in an electric field.
Example:
Water has a high electric permittivity, which is why it's effective at dissolving ionic compounds by weakening the electric forces between ions.
Electric field strength
The magnitude of the electric field at a point, defined as the electric force per unit positive test charge at that point.
Example:
Near a Van de Graaff generator, the electric field strength is very high, causing hair to stand on end.
Electric fields
A vector field that describes the electric force per unit charge at every point in space around a charged object.
Example:
The region around a charged comb that attracts small pieces of paper is an electric field.
Electric flux density
A measure of the electric field in a dielectric medium, representing the amount of electric field lines passing through a given area.
Example:
In a capacitor, the electric flux density is uniform between the plates, indicating a consistent electric field.
Electric potential energy
The energy stored in a system of charged particles due to their positions relative to each other within an electric field.
Example:
Two like charges held close together have high electric potential energy because they will repel each other if released.
Electric systems
Systems where charged particles interact through electric fields, leading to forces and potential differences.
Example:
A lightning strike is a dramatic example of an electric system in action, where massive amounts of charge are transferred.
Electromagnetic force
One of the four fundamental forces of nature, responsible for interactions between charged particles, encompassing both electric and magnetic phenomena.
Example:
The electromagnetic force holds atoms and molecules together, giving matter its structure and properties.
Electromagnetism
The branch of physics that studies the interactions between electric currents and magnetic fields, and how charged particles produce and are affected by these fields.
Example:
An MRI machine uses principles of electromagnetism to create detailed images of the inside of the human body.
Field
A physical quantity that has a value for each point in space and time, used to describe how a force or influence is distributed.
Example:
A weather map showing temperature at different locations represents a temperature field.
Field Lines
Imaginary lines used to visualize electric fields, where the direction of the line indicates the direction of the field and the density of the lines indicates the field strength.
Example:
Around a positive point charge, field lines radiate outwards, showing the direction a positive test charge would move.
Force
A push or pull that can cause an object with mass to accelerate, change velocity, or deform.
Example:
When you kick a soccer ball, you apply a force that causes it to move.
Free-Body Diagrams
Visual representations used in physics to show all the forces acting on a single object, typically drawn as arrows originating from the object's center of mass.
Example:
To analyze the forces on a car going around a turn, a free-body diagram would show gravitational force, normal force, and friction.
Friction (charge distribution)
A method of charging objects by rubbing them together, causing electrons to transfer from one surface to another.
Example:
Rubbing a balloon on your hair charges the balloon through friction, allowing it to stick to a wall.
Gravitational force
The attractive force that exists between any two objects with mass, proportional to their masses and inversely proportional to the square of the distance between them.
Example:
The gravitational force between the Earth and the Moon keeps the Moon in orbit.
Inductance
The property of an electrical conductor by which a change in current flowing through it induces an electromotive force (voltage) in the conductor itself or in a neighboring conductor.
Example:
The inductance of a coil determines how effectively it can resist changes in current flow.
Induction (charge distribution)
A method of charging an object without direct contact, where a nearby charged object causes a redistribution of charges within the neutral object.
Example:
Bringing a negatively charged rod near a neutral electroscope will cause the leaves to repel due to induction, even without touching.
Inductors
Passive electrical components, typically coils of wire, that store energy in a magnetic field when electric current flows through them.
Example:
An inductor in a car's ignition system helps create the high voltage spark needed to ignite the fuel.
Isolines
Lines on a diagram or map that connect points of equal value for a given quantity in a field.
Example:
On a topographic map, contour lines are isolines connecting points of equal elevation.
Maxwell's Equations
A set of four fundamental equations that describe how electric and magnetic fields are generated and interact, forming the basis of classical electromagnetism.
Example:
The propagation of radio waves through the air is perfectly described by Maxwell's Equations.
Potential Energy
Energy stored in an object due to its position, configuration, or state, with the capacity to do work.
Example:
A stretched rubber band has stored potential energy that can be converted into kinetic energy when released.
Resistance
A measure of the opposition to the flow of electric current in an electrical circuit, measured in Ohms (Ω).
Example:
A long, thin wire has higher resistance than a short, thick wire, making it harder for current to pass through.
Resistors
Passive electrical components that oppose the flow of electric current in a circuit, converting electrical energy into heat.
Example:
A dimmer switch for a light uses a resistor to control the brightness by varying the current.
Scalar Field
A field that assigns a single scalar value (a magnitude without direction) to every point in space.
Example:
The temperature distribution in a room is a scalar field, where each point has a specific temperature value.
Vector Field
A field that assigns a vector (a quantity with both magnitude and direction) to every point in space.
Example:
The flow of water in a river can be described by a vector field, where each point has a specific velocity (speed and direction).
Vectors (electric forces)
Quantities that have both magnitude and direction, used to represent electric forces, electric fields, and other directional physical quantities.
Example:
When calculating the net force on a charge from multiple other charges, you must add the individual vectors representing each electric force.
Voltage
Also known as electric potential difference, it is the work done per unit charge to move a test charge between two points in an electric field.
Example:
A 9V battery provides a voltage of 9 volts, pushing charges through a circuit.
Work
The energy transferred to or from an object by means of a force acting on the object over a displacement.
Example:
Lifting a heavy box off the floor requires you to do work against gravity.