Physics: Electricity, Magnetism, and Optics (Chapters 18-26)

Vocabulary-style flashcards covering electricity, magnetism, geometric optics, and induction based on study notes for Chapters 18 through 26.

Electric charge

A property of matter that comes in two types, positive (+) and negative (-), where opposites attract and like charges repel.

Coulomb ($C$)

The SI unit of charge; one elementary charge $q_e$ is equal to $1.60 imes 10^{-19} C$, which is the same for protons and electrons except for the sign.

Law of conservation of charge

The principle stating that in all situations, the total amount of charge is always constant.

Conductor

A material that has free electrons and allows charge to move relatively freely through it, such as salty water or molten salt.

Insulator

A material that does not allow charges to move through it, such as pure water or table salt.

Coulomb's Law

The law describing the electrostatic force between two point charges: F = k rac{|q_1 q_2|}{r^2}, where $k = 8.99 imes 10^9 N \cdot m^2$.

Electric field ($E$)

A vector field measured in $N/C$ representing the force per unit charge locally, defined by $E = \frac{F}{q}$ for a test charge.

Electric field lines

Lines that represent the direction and strength of the electric field; they must originate on positive charges, terminate on negative charges, and never cross.

Electric potential energy ($PE$)

Energy associated with the arrangement of charges, where the work done on a charge is given by $W = -\Delta PE$.

Electric potential ($V$)

The quantity representing potential energy per unit charge, defined as $V = \frac{PE}{q}$, often measured as voltage ($\text{pot. diff.}$).

Electron volt ($eV$)

The energy given to a fundamental charge accelerated through a potential difference of $1 V$, equal to $1.60 imes 10^{-19} J$.

Equipotential lines

Lines across which the electric potential is constant and work required to move a charge is zero ($\Delta V = 0, W = 0$); they are perpendicular to electric field lines.

Capacitor

A device used to store electric charge, typically consisting of two identical parallel conducting plates.

Capacitance ($C$)

The amount of charge stored per volt, measured in farads ($F$), where $C = \frac{Q}{V}$.

Dielectric

A material placed between the plates of a capacitor that makes the distance $d$ effectively smaller and increases the capacitance.

Electric current ($I$)

The rate at which charge flows through a given area, measured in Amperes ($A$), defined by $I = \frac{\Delta q}{t}$.

Resistance ($R$)

A measure of how much a device impedes current, measured in ohms ($\Omega$), where $R = \frac{V}{I}$ according to Ohm's Law.

Resistivity ($\rho$)

A property of a material indicating its resistance based on temperature and geometry, used in the formula $R = \rho \frac{L}{A}$.

Electric power ($P$)

The rate of energy transfer in a circuit, measured in Watts ($W$) and given by the formulas $P = IV$, $P = \frac{V^2}{R}$, or $P = I^2 R$.

Kirchoff's Junction Rule

The sum of all currents entering a junction must equal the sum of all currents leaving the junction ($I_1 = I_2 + I_3$).

Kirchoff's Loop Rule

The algebraic sum of changes in potential around any closed circuit path (loop) must be zero.

Electromotive force ($V_{emf}$)

The potential difference provided by batteries or generators that adds energy to a circuit; terminal voltage is expressed as $V = emf - Ir$.

Time constant ($\tau$)

For an RC circuit, defined as $\tau = RC$, it is the time at which the voltage rises to $63.2\%$ of its final value during charging.

Lorentz Force

The magnitude of the magnetic force on a charge $q$ moving at speed $v$ in a magnetic field strength $B$, given by $F = |q| v B \sin(\theta)$.

Hall Effect

The creation of a voltage (Hall emf) across a current-carrying conductor by a magnetic field, resulting from the separation of charges.

Faraday's law of induction

The law stating that an electromotive force is induced by a change in magnetic flux over time: $emf = -N \frac{\Delta \Phi}{\Delta t}$.

Lenz's Law

The rule that an induced emf creates a current and magnetic field that oppose the change in magnetic flux that produced it.

Self-inductance ($L$)

The effect of Faraday's law of induction where a device induces an emf on itself, measured in henries ($H$), as $emf = -L \frac{\Delta I}{\Delta t}$.

Accommodation

The process by which the human eye adjusts its focal length to maintain clear vision of objects at various distances.

Myopia

Nearsightedness, a condition where the eye overconverges light rays, making distant objects appear blurry.

Hyperopia

Farsightedness, a condition where the eye underconverges light rays, making close objects appear blurry.

Real image

An image formed by light rays actually passing through a location, allowing it to be projected onto a screen or retina.

Virtual image

An image formed at a location where light rays only appear to originate; it cannot be projected onto a screen.

Dispersion

The spreading of white light into its full spectrum of wavelengths as the light rays refract.