Glossary
Amplitude
The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position.
Example:
A loud sound wave has a larger Amplitude than a quiet sound wave.
Charging by Conduction
The process of charging an object by direct physical contact with a charged object, leading to a redistribution of charge until equilibrium is reached.
Example:
Touching a charged metal rod to a neutral sphere will cause charge to transfer, leaving the sphere with a net charge through Charging by Conduction.
Conductors
Materials that allow electric charge to move freely through them due to the presence of free electrons.
Example:
Metals like copper and silver are excellent Conductors, which is why they are used for electrical wiring.
Conservation of Electric Charge
The fundamental principle stating that the total electric charge in a closed system remains constant; charge can only be transferred, not created or destroyed.
Example:
When you rub a balloon on your hair, charge is transferred between them, but the total amount of charge in the balloon-hair system remains constant, demonstrating the principle of Conservation of Electric Charge.
Coulomb's Constant
The proportionality constant 'k' in Coulomb's Law, which relates the electrostatic force to the magnitudes of charges and the distance between them.
Example:
The value of Coulomb's Constant is approximately 8.99 × 10^9 N·m²/C², a crucial number for calculating forces between charges.
Coulomb's Law
A fundamental law describing the electrostatic force between two point charges, stating it is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.
Example:
According to Coulomb's Law, if you double the distance between two charged particles, the electrostatic force between them decreases by a factor of four.
Current
The rate of flow of electric charge through a conductor, measured in Amperes (A).
Example:
When you turn on a light switch, electrons begin to flow through the wires, creating an electric Current.
Diffraction
The bending of waves as they pass around obstacles or through small openings, demonstrating the wave nature of light.
Example:
When light passes through a narrow slit, it spreads out, creating a pattern of bright and dark fringes due to Diffraction.
Electric Field
A region of space around a charged object where another charged particle would experience an electrostatic force.
Example:
A positive point charge creates an Electric Field that points radially outward from it, influencing any other charges placed in its vicinity.
Electric Potential
The electric potential energy per unit charge at a specific point in an electric field, often referred to as voltage.
Example:
A high Electric Potential at a point indicates that a positive test charge placed there would have a large amount of potential energy.
Electric Potential Energy
The energy a charge possesses due to its position in an electric field, representing the work done to move the charge to that position.
Example:
When you lift a positive charge against an electric field, you increase its Electric Potential Energy, similar to increasing gravitational potential energy by lifting an object.
Electrical Resistance
A measure of a material's opposition to the flow of electric current, determined by its resistivity, length, and cross-sectional area.
Example:
A long, thin wire will have higher Electrical Resistance than a short, thick wire of the same material.
Electromagnetic Induction
The process by which a changing magnetic field through a circuit induces an electromotive force (EMF) and thus an electric current.
Example:
Moving a magnet back and forth through a coil of wire generates electricity through Electromagnetic Induction, the principle behind electric generators.
Electron Mobility
The ease with which electrons can move through a material in response to an electric field.
Example:
In a conductor, electrons have high Electron Mobility, allowing current to flow easily, whereas in an insulator, it is very low.
Electrostatic Force
The attractive or repulsive force between charged objects, governed by Coulomb's Law.
Example:
The attraction between a positively charged proton and a negatively charged electron is an Electrostatic Force.
Energy (in circuits)
The total amount of electrical work done or consumed over a period of time in a circuit, measured in Joules (J).
Example:
Your electricity bill charges you based on the total Energy (in circuits) consumed by your household appliances over a month.
Energy Levels (atomic)
Specific, discrete amounts of energy that electrons can possess within an atom, corresponding to stable orbits or states.
Example:
When an electron jumps from a higher to a lower Energy Level (atomic), it emits a photon of specific energy, creating distinct spectral lines.
Equipotential Surfaces
Surfaces in an electric field where all points have the same electric potential, and electric field lines are always perpendicular to them.
Example:
For a single point charge, concentric spheres around the charge represent Equipotential Surfaces, as the potential is constant at any given radius.
Faraday's Law
A law stating that the magnitude of the induced electromotive force (EMF) in a circuit is directly proportional to the rate of change of magnetic flux through the circuit.
Example:
Faraday's Law explains why a rapidly changing magnetic field produces a larger induced voltage than a slowly changing one.
Frequency
The number of complete oscillations or cycles of a wave that pass a point per unit of time, measured in Hertz (Hz).
Example:
A radio station broadcasts at a specific Frequency, like 98.7 MHz, which your radio tuner picks up.
Grounding
The process of connecting an object to a large reservoir of charge, like the Earth, to allow excess charge to flow to or from it, neutralizing the object.
Example:
To safely discharge a charged object, you can connect it to the Earth with a wire, allowing the excess charge to flow away through Grounding.
Induced EMF
The electromotive force (voltage) generated in a circuit due to a changing magnetic flux, which can drive an induced current.
Example:
When you wave a metal detector over buried treasure, the changing magnetic field creates an Induced EMF in the coil, signaling the presence of metal.
Induction
The process by which a charged object causes a separation of charge in a nearby neutral object without direct contact.
Example:
Holding a negatively charged rod near a neutral electroscope will cause the leaves to repel due to charge separation within the electroscope, an example of Induction.
Insulators
Materials that resist the flow of electric charge because their electrons are tightly bound and cannot move freely.
Example:
Rubber gloves and plastic coatings on wires act as Insulators, preventing electric shocks.
Interference
The phenomenon that occurs when two or more waves superpose to form a resultant wave of greater, lower, or the same amplitude.
Example:
The colorful patterns seen in soap bubbles are a result of light wave Interference.
Lenz's Law
A law stating that the direction of an induced current or EMF is always such that it opposes the change in magnetic flux that produced it.
Example:
If you drop a strong magnet through a copper pipe, it falls slowly because the induced current creates a magnetic field that opposes the magnet's motion, illustrating Lenz's Law.
Magnetic Fields
Regions of space around a magnet or a moving electric charge where magnetic forces are exerted on other moving charges or magnetic materials.
Example:
The Earth itself generates a large Magnetic Field that protects us from solar radiation and guides compasses.
Magnetic Flux
A measure of the total number of magnetic field lines passing through a given area, indicating the strength of the magnetic field over that area.
Example:
Tilting a coil of wire in a uniform magnetic field changes the Magnetic Flux through it, which can induce a current.
Magnetic Force (on current-carrying wire)
The force exerted on a wire carrying electric current when placed in a magnetic field, which is the basis for electric motors.
Example:
An electric motor works by using the Magnetic Force (on current-carrying wire) to produce rotational motion.
Magnetic Force (on moving charge)
The force exerted on a charged particle moving through a magnetic field, perpendicular to both the velocity of the charge and the magnetic field.
Example:
The aurora borealis is caused by charged particles from the sun experiencing a Magnetic Force (on moving charge) as they enter Earth's magnetic field.
Mass-Energy Equivalence
The principle, famously expressed by E=mc², stating that mass and energy are interchangeable and can be converted into one another.
Example:
In a nuclear bomb, a tiny amount of mass is converted into an enormous amount of energy, demonstrating Mass-Energy Equivalence.
Nuclear Physics
The branch of physics concerned with the structure, properties, and reactions of atomic nuclei.
Example:
Nuclear Physics is crucial for understanding processes like radioactive decay and nuclear fusion in stars.
Nuclear Reactions
Processes that involve changes in the composition of atomic nuclei, often resulting in the release or absorption of large amounts of energy.
Example:
Both nuclear fission in power plants and nuclear fusion in the sun are examples of powerful Nuclear Reactions.
Ohm's Law
A fundamental law in circuits stating that the voltage across a conductor is directly proportional to the current flowing through it, given by V = IR.
Example:
If a circuit has a 12V battery and a 4Ω resistor, Ohm's Law tells us the current will be 3 Amperes.
Parallel Circuits
Circuits where components are connected across the same two points, so the voltage is the same across each component, and the total resistance is calculated using reciprocals.
Example:
Household electrical outlets are wired in Parallel Circuits, ensuring that each appliance receives the full voltage from the power source.
Permanent Magnets
Materials that produce their own persistent magnetic fields due to the alignment of their internal atomic magnetic moments.
Example:
The magnets on your refrigerator door are Permanent Magnets, always exerting a magnetic force.
Photons
Discrete packets or quanta of light energy, which also exhibit wave-like properties.
Example:
When light hits a solar panel, individual Photons transfer their energy to electrons, generating electricity.
Planck's Constant
A fundamental physical constant (h) that relates the energy of a photon to its frequency (E = hf), central to quantum mechanics.
Example:
Planck's Constant is a tiny number (6.626 × 10^-34 J·s) that highlights the quantized nature of energy at the atomic scale.
Potential Difference
The difference in electric potential between two points in an electric field, representing the work done per unit charge to move a charge between those points.
Example:
A 9-volt battery creates a Potential Difference of 9 volts between its terminals, driving current through a circuit.
Power (in circuits)
The rate at which electrical energy is consumed or supplied in a circuit, measured in Watts (W).
Example:
A 100-watt light bulb consumes electrical Power (in circuits) at a rate of 100 Joules per second.
Primary Coil
The input coil of a transformer, connected to the alternating current source.
Example:
The number of turns in the Primary Coil relative to the secondary coil determines whether a transformer steps voltage up or down.
Primary Voltage
The input voltage applied to the primary coil of a transformer.
Example:
In a step-down transformer, the Primary Voltage is higher than the output voltage.
Quantum Physics
The branch of physics that studies the behavior of matter and energy at the atomic and subatomic levels, where classical physics breaks down.
Example:
Quantum Physics explains phenomena like the photoelectric effect and the discrete energy levels of atoms.
Radioactivity
The spontaneous emission of particles or energy from unstable atomic nuclei as they undergo decay to become more stable.
Example:
Carbon-14 dating relies on the predictable Radioactivity of carbon isotopes to determine the age of ancient artifacts.
Reflection
The phenomenon of a wave bouncing off a surface or boundary, with the angle of incidence equaling the angle of reflection.
Example:
When you look in a mirror, you are seeing your image formed by the Reflection of light.
Refraction
The bending of a wave as it passes from one medium into another, caused by a change in the wave's speed.
Example:
A straw in a glass of water appears bent due to the Refraction of light as it passes from water to air.
Refractive Index
A dimensionless number that describes how fast light travels through a medium, relative to its speed in a vacuum.
Example:
Diamonds have a very high Refractive Index, which contributes to their sparkle.
Resistance
The opposition to the flow of electric current in a circuit, measured in Ohms (Ω).
Example:
A dimmer switch increases the Resistance in a light circuit, reducing the current and dimming the light.
Secondary Coil
The output coil of a transformer, where the induced voltage is produced.
Example:
The voltage induced in the Secondary Coil is proportional to the ratio of its turns to the primary coil's turns.
Secondary Voltage
The output voltage produced across the secondary coil of a transformer.
Example:
A phone charger's transformer reduces the wall's 120V to a much lower Secondary Voltage suitable for charging your device.
Series Circuits
Circuits where components are connected end-to-end, so the current is the same through each component, and total resistance is the sum of individual resistances.
Example:
In a string of old Christmas lights, if one bulb burns out, the entire string goes dark because they are connected in Series Circuits.
Snell's Law
A formula used to describe the relationship between the angles of incidence and refraction, and the refractive indices of two media.
Example:
Engineers use Snell's Law to design lenses that correctly focus light.
Solenoids
Coils of wire that produce a strong, uniform magnetic field inside them when an electric current passes through.
Example:
Electromagnets often use Solenoids to create a controllable magnetic field for lifting heavy scrap metal.
Tesla (unit)
The SI unit of magnetic field strength, representing one Newton per Ampere-meter.
Example:
A strong MRI machine can generate a magnetic field of several Tesla (unit), much stronger than a typical refrigerator magnet.
Transformers
Electrical devices that use electromagnetic induction to change (step up or step down) the voltage of an alternating current.
Example:
Power lines use large Transformers to step up voltage for efficient long-distance transmission and then step it down for safe use in homes.
Wave Speed
The speed at which a wave propagates through a medium, calculated as the product of its frequency and wavelength (v = fλ).
Example:
The Wave Speed of light in a vacuum is a constant, approximately 3 x 10^8 m/s.
Wave-Particle Duality
The concept in quantum mechanics that all particles exhibit both wave and particle properties.
Example:
Electrons, typically thought of as particles, can also exhibit Wave-Particle Duality by diffracting like waves when passed through a crystal lattice.
Wavelength
The spatial period of a wave, which is the distance over which the wave's shape repeats, typically measured from crest to crest or trough to trough.
Example:
Red light has a longer Wavelength than blue light, which is why they appear as different colors.