Glossary
Batteries
Electrochemical devices that store chemical energy and convert it into electrical energy through chemical reactions.
Example:
Your phone is powered by a lithium-ion battery that provides a steady voltage.
Capacitance
A measure of a capacitor's ability to store electric charge per unit of potential difference across its plates.
Example:
A large capacitance means a capacitor can store a significant amount of charge for a given voltage.
Capacitor
A passive electronic component designed to store electrical energy in an electric field by accumulating electric charge on two closely spaced conductors.
Example:
A camera flash uses a capacitor to quickly release a burst of stored energy to power the light.
Charge
A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field.
Example:
Rubbing a balloon on your hair transfers charge, causing the balloon to stick to a wall.
Conservation of Charge
The principle stating that the total electric charge in an isolated system remains constant; charge cannot be created or destroyed, only transferred.
Example:
When you rub a balloon on your hair, the total charge of the balloon-hair system remains constant, illustrating the conservation of charge.
Conventional Current
The direction in which positive charges would flow, defined as opposite to the actual flow of electrons in most conductors.
Example:
Even though electrons move from negative to positive, we define conventional current as flowing from positive to negative.
Coulomb's Law
A fundamental law describing the magnitude of the electrostatic force between two point charges, which is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.
Example:
Coulomb's Law explains why two positively charged particles repel each other with a force that weakens rapidly as they move apart.
Current-Carrying Wire (as a source of B-field)
A conductor through which electric current flows, generating a magnetic field in concentric circles around it.
Example:
Wrapping a current-carrying wire around an iron core creates a simple electromagnet.
Electric Charges
Fundamental properties of subatomic particles, existing as positive (protons) or negative (electrons), which interact via electromagnetic forces.
Example:
Static electricity occurs when there is an imbalance of electric charges on a surface.
Electric Circuits
Closed loops of interconnected components that allow electric current to flow, facilitating the transfer of electrical energy.
Example:
Household wiring forms complex electric circuits to power lights and appliances.
Electric Current
The rate of flow of electric charge through a conductor, measured in amperes (A).
Example:
When you turn on a light switch, electric current flows through the bulb's filament, causing it to glow.
Electric Fields
Regions of space around charged objects where other charged objects would experience an electric force.
Example:
A charged comb creates an electric field that can attract small pieces of paper.
Electric Generators
Devices that convert mechanical energy into electrical energy, typically by rotating coils of wire within a magnetic field.
Example:
Large wind turbines use electric generators to produce electricity from wind power.
Electric Motors
Devices that convert electrical energy into mechanical energy, using the interaction between magnetic fields and electric currents.
Example:
The fan in your computer uses an electric motor to spin its blades and cool the components.
Electric Potential
The amount of electric potential energy per unit charge at a specific point in an electric field, often referred to as voltage.
Example:
A high electric potential difference across a light bulb drives current through it, causing it to glow.
Electric Potential Energy
The energy a charged particle possesses due to its position within an electric field, representing the work done to move the charge to that position.
Example:
A positive charge held near another positive charge has high electric potential energy, similar to a ball at the top of a hill.
Electric Power
The rate at which electrical energy is converted into other forms of energy (e.g., heat, light, mechanical work) in an electrical circuit.
Example:
A light bulb's wattage rating indicates its electric power consumption, showing how quickly it converts electrical energy into light and heat.
Electromagnet
A type of magnet in which the magnetic field is produced by an electric current, allowing its strength to be controlled by varying the current.
Example:
Scrap yards use powerful electromagnets to lift and move heavy metal objects.
Electromagnetism
The fundamental force of nature that describes the interaction between electrically charged particles, encompassing both electric and magnetic phenomena.
Example:
Understanding electromagnetism is crucial for designing everything from simple doorbells to complex particle accelerators.
Energy Stored in a Capacitor
The electrical potential energy accumulated within a capacitor's electric field when it is charged.
Example:
The energy stored in a capacitor is released when it discharges, for instance, powering a defibrillator.
Faraday's Law of Induction
A fundamental law of electromagnetism stating that a changing magnetic flux through a circuit induces an electromotive force (EMF) or voltage in that circuit.
Example:
Moving a magnet back and forth through a coil of wire generates an electric current, as described by Faraday's Law of Induction.
Field Lines
Imaginary lines used to visualize electric or magnetic fields, where the direction of the line indicates the field's direction and the density of lines indicates its strength.
Example:
Drawing field lines around a positive charge shows them radiating outwards, indicating the direction a positive test charge would move.
Kirchhoff's Junction Rule
A rule stating that the sum of currents entering a junction (node) in an electrical circuit must equal the sum of currents leaving the junction, based on the conservation of charge.
Example:
If 5 amps flow into a circuit branch, then 5 amps must flow out of that branch, as dictated by Kirchhoff's Junction Rule.
Kirchhoff's Loop Rule
A rule stating that the algebraic sum of the potential differences (voltages) around any closed loop in an electrical circuit must be zero, based on the conservation of energy.
Example:
Tracing a path around a circuit, the voltage gains from batteries must equal the voltage drops across resistors, according to Kirchhoff's Loop Rule.
Lenz's Law
A law that specifies the direction of the induced current or EMF, stating that it will always oppose the change in magnetic flux that produced it.
Example:
When you drop a magnet through a copper pipe, it falls slowly because of the opposing magnetic field created by the induced current, illustrating Lenz's Law.
Magnetic Field
A region of space around a magnet or a current-carrying conductor where magnetic forces can be detected.
Example:
A compass needle aligns itself with the Earth's magnetic field.
Magnetic Field Lines
Imaginary lines used to represent the direction and strength of a magnetic field, pointing from the north pole to the south pole outside a magnet and forming closed loops.
Example:
Sprinkling iron filings around a bar magnet reveals the pattern of its magnetic field lines.
Magnetic Flux
A measure of the total number of magnetic field lines passing through a given area, quantifying the amount of magnetic field penetrating a surface.
Example:
Changing the orientation of a coil in a magnetic field alters the magnetic flux through it, inducing a current.
Magnetic Force on a Current-Carrying Wire
The force experienced by a segment of wire carrying electric current when placed within a magnetic field.
Example:
The operation of an electric motor relies on the magnetic force on a current-carrying wire to produce rotational motion.
Magnetic Force on a Moving Charge
The force experienced by a charged particle moving through a magnetic field, which is perpendicular to both the velocity of the charge and the magnetic field.
Example:
The deflection of electrons in a cathode ray tube is due to the magnetic force on a moving charge.
Mass
A fundamental property of matter that quantifies its inertia and its gravitational interaction.
Example:
A bowling ball has significantly more mass than a tennis ball, making it harder to accelerate.
Object
A collection of matter, which can be a single entity or multiple entities grouped together for study.
Example:
In a circuit, a single resistor can be considered an object.
Ohm's Law
A fundamental law in circuit analysis stating that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them (V=IR).
Example:
Ohm's Law allows you to calculate the current flowing through a circuit if you know the voltage of the battery and the total resistance.
Parallel Circuit
A circuit configuration where components are connected across the same two points, providing multiple paths for current flow, so the voltage across each component is the same.
Example:
Most household electrical outlets are wired in a parallel circuit, allowing multiple appliances to receive the full line voltage independently.
Parallel Plate Capacitor
A type of capacitor consisting of two parallel conductive plates separated by a dielectric material or vacuum, commonly used in electronic circuits.
Example:
The formula C = ε₀A/d is used to calculate the capacitance of a parallel plate capacitor.
Potential Difference
The difference in electric potential between two points in an electric field, also known as voltage, which drives the flow of charge.
Example:
A 9V battery creates a potential difference of 9 volts between its terminals, pushing current through a circuit.
Quantization of Charge
The principle that electric charge exists only in discrete, integer multiples of the elementary charge (e), the charge of a single proton or electron.
Example:
You cannot have a charge of 0.5e; charge always comes in whole units due to the quantization of charge.
RC Circuit
An electrical circuit composed of at least one resistor and one capacitor, exhibiting exponential charging and discharging behavior.
Example:
An RC circuit is used in timing applications, such as controlling the blink rate of an LED.
Resistance
The opposition a material offers to the flow of electric current, converting electrical energy into heat.
Example:
A toaster works by using a high resistance heating element to generate heat from electric current.
Resistivity
An intrinsic material property that quantifies how strongly a given material opposes the flow of electric current.
Example:
Copper has low resistivity, making it an excellent material for electrical wires, while rubber has very high resistivity.
Series Circuit
A circuit configuration where components are connected end-to-end along a single path, so the same current flows through each component.
Example:
Old Christmas lights were often wired in a series circuit; if one bulb burned out, the entire string would go dark.
Solenoid
A coil of wire typically wound into a tightly packed helix, which produces a strong and uniform magnetic field inside when current flows through it.
Example:
A solenoid is often used as an electromagnet to operate a switch or valve.
Step-Down Transformer
A type of transformer that decreases the voltage from the primary coil to the secondary coil, typically by having fewer turns in the secondary coil.
Example:
The charger for your laptop contains a step-down transformer to reduce the wall voltage to a level safe for your device.
Step-Up Transformer
A type of transformer that increases the voltage from the primary coil to the secondary coil, typically by having more turns in the secondary coil.
Example:
Power plants use a step-up transformer to increase the voltage of generated electricity for efficient long-distance transmission.
System
A collection of objects being studied as a whole, defined by its physical or conceptual boundaries.
Example:
When analyzing a car's electrical components, the entire car's wiring and devices form an electrical system.
Time Constant
A characteristic time for an RC circuit, equal to the product of resistance and capacitance (τ = RC), representing the time it takes for the capacitor to charge or discharge to a certain percentage of its maximum or initial value.
Example:
A large time constant in an RC circuit means the capacitor will take a longer time to fully charge or discharge.
Transformer
An electrical device that uses electromagnetic induction to transfer electrical energy between two or more circuits, typically to change the voltage of an alternating current.
Example:
Power lines use a transformer to step down high voltages to safer levels for household use.
Uniform Electric Field
An electric field where the magnitude and direction of the field are constant throughout a specific region of space.
Example:
The space between two large, parallel, oppositely charged plates creates a nearly uniform electric field.