PHYS 212: Electricity and Magnetism

Flashcards covering key concepts and definitions from the PHYS 212 lecture notes.

Electric Charge

Electric charges can cause objects to be repelled from each other or to be attracted to each other.

Amber and Fur

When amber is rubbed with fur, amber gains electrons becoming negatively charged, and fur loses electrons becoming positively charged.

Charge Separation

When materials are rubbed together, charges can be separated, particularly if one material has a greater affinity for electrons than another.

Electric Force Observations

The electric force acts without physical contact, can be attractive or repulsive based on charge signs, and decreases with distance.

Electrostatic Repulsion

The force between two interacting objects carrying the same sign of charge.

Electrostatic Attraction

The force between two interacting objects carrying opposite signs of charge.

Charge Quantization

The smallest possible amount of charge that an object can have is e = 1.602 × 10-19 C, and all macroscopic charged objects are an integer multiple of this amount.

Charge Conservation

Charge can neither be created nor destroyed; it can only be transferred from place to place, from one object to another.

Structure of the Atom

Atoms consist of a positively charged nucleus surrounded by an electron cloud with an equal but opposite charge.

Conductors

Materials in which charge flows freely such as metals, water, and the human body.

Insulators

Materials in which almost no charge flows such as wood, glass, plastic, and rubber.

Induced Polarization

The redistribution of charges in a neutral object due to the presence of a nearby charged object.

Charging by Induction

Charging an object without touching it with a charged object, involving separation of charge and grounding.

Coulomb's Law

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

Permittivity of Vacuum

ε₀ = 8.85 × 10⁻¹² C²/Nm², used in Coulomb's Law.

Coulomb Constant

k = 1/4πε₀ ≈ 8.99 × 10⁹ Nm²/C², used to simplify Coulomb's Law.

Principle of Superposition

The net electric force on a test charge due to multiple source charges is the vector sum of each individual electric force exerted on it.

Electric Field (E)

The force per unit charge exerted on a test charge at a given point in space.

Vector Field

A quantity that has both magnitude and direction at every point in space.

Continuous Charge Distributions

Distributions of charge over a line, surface, or volume, described by linear, surface, or volume charge density.

Linear Charge Density (λ)

Charge per unit length (λ = Q/L or dq/dl).

Surface Charge Density (σ)

Charge per unit area (σ = Q/A or dq/dA).

Volume Charge Density (ρ)

Charge per unit volume (ρ = Q/V or dq/dV).

Electric Field Lines

Lines that represent the direction and magnitude of an electric field, with density proportional to field strength.

Electric Dipole

A pair of equal but opposite charges separated by a distance.

Dipole Moment (p)

A measure of the polarity of a molecule; for two charges, p = qd.

Induced Dipole

A dipole created in a neutral atom or molecule by an external electric field.

Electric Flux (Φ)

A measure of the number of electric field lines passing through a surface area.

Area Vector (A)

A vector with magnitude equal to the area of a surface and direction perpendicular to the surface.

Gaussian Surface

A closed surface used in Gauss's Law to calculate the electric flux.

Gauss's Law

The total electric flux through a closed surface is proportional to the enclosed electric charge (Φ = Qenc/ε₀).

Spherical Symmetry

Symmetry in which the charge density depends only on the radial distance from the center.

Cylindrical Symmetry

Symmetry in which the charge density does not depend on the polar angle or along the axis.

Planar Symmetry

Symmetry in which charges are uniformly spread over a large flat surface.

Electrostatic Equilibrium

The condition where there is no net motion of charge within a conductor.

Equipotential Surface

A surface on which the electric potential is constant.

Electric Potential Energy (U)

The potential energy possessed by a charge due to its location in an electric field.

Electric Potential (V)

The electric potential energy per unit charge (V = U/q).

Electron-Volt (eV)

The energy gained by an electron when it moves through a potential difference of 1 volt (1 eV = 1.60 × 10⁻¹⁹ J).

Capacitor

A device used to store electrical charge and electrical energy.

Capacitance (C)

The ratio of charge stored on a capacitor to the voltage across it (C = Q/V).

Farad (F)

The unit of capacitance (1 F = 1 C/V).

Dielectric

An insulating material placed between the plates of a capacitor.

Dielectric Constant (κ)

A factor by which the capacitance increases when a dielectric is inserted between the plates of a capacitor.

Dielectric Strength

The maximum electric field that a dielectric can withstand before breakdown occurs.

Electrical Current (I)

The rate at which charge flows through a given cross-sectional area (I = dQ/dt).

Ampere (A)

The unit of current (1 A = 1 C/s).

Drift Velocity (vd)

The average velocity of free charges in a conductor due to an electric field.

Current Density (J)

The current per unit area in a conductor (J = I/A).

Electrical Conductivity (σ)

A measure of a material's ability to conduct electricity.

Resistivity (ρ)

A measure of how strongly a material opposes the flow of current (ρ = 1/σ).

Ohm (Ω)

The unit of resistance (1 Ω = 1 V/A).

Resistance (R)

A measure of how difficult it is to pass current through a wire or component (R = V/I).

Ohm's Law

The voltage across a resistor is directly proportional to the current through it (V = IR).

Electrical Power (P)

The rate at which electrical energy is converted to other forms of energy (P = IV).

Electromotive Force (emf) (ε)

A voltage source, such as a battery, that can supply current to a circuit.

Internal Resistance (r)

Resistance within a battery or other voltage source that reduces the terminal voltage.

Kirchhoff's Rules

A set of rules used to analyze complex circuits, including the junction rule and the loop rule.

Ammeter

A device used to measure the current through a component in a circuit.

Voltmeter

A device used to measure the voltage across a component in a circuit.

Ohmmeter

A device used to measure the resistance of a component.

RC Circuit

A circuit that contains both resistance and capacitance.

Time Constant (τ)

A measure of how quickly a capacitor charges or discharges in an RC circuit (τ = RC).

Magnetism

A physical phenomenon produced by the motion of electric charge, resulting in attractive and repulsive forces.

Magnetic Poles

The points on a magnet where the magnetic field is strongest, labeled north (N) and south (S).

Magnetic Field (B)

The area around a magnet where a magnetic force is exerted.

Tesla (T)

The SI unit of magnetic field strength.

Gauss (G)

A unit of magnetic field strength (1 G = 10⁻⁴ T).

Right-Hand Rule

A mnemonic used to determine the direction of magnetic forces and fields.

Magnetic Force

The force exerted on a moving charge or current-carrying wire in a magnetic field.

Period (T)

The time for one complete cycle of periodic motion.

Magnetic Force on a Current-Carrying Conductor

A wire in a magnetic field experiences a force proportional to the current, length, and field strength.

Lorentz Force

The combination of electric and magnetic forces on a point charge.

Torque ()

A rotational force that causes an object to rotate.

Biot-Savart Law

describes the magnetic field generated by an electric current.

Ampère's Law

relates the integrated magnetic field around a closed loop to the electric current passing through the loop.

Solenoids

an electrical component comprising a coil of wire whose terminals are designed to carry or generate a magnetic field.

Toroids

A coil wound in a ring to create different magnetic fields.

Faraday's Law

A basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF)."

Lenz's Law

a common law of physics stating that the direction of the electric current induced in a closed circuit by a changing magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field

Motional EMF

The electromotive force (EMF) induced because movement of the conductor through magnetic or vice versa

Eddy Current

The electric current induced that flows in a loop from a conductor to a magnetic field.

Electric Generators

A machine converts mechanical energy into electrical energy.

Mutual inductance

the ratio of the emf in the device to rate of change of potential in the other

Self-inductance

An electromotive force (Electromotive Force) is induced in the current carrying wire itself when the magnetic flux thrugh the circuit is varied either by moving the circuit or varying a field

RL Circuits

A circuit containing a resistor or a inductor.

LC Circuits

A circuit containing a capicator and inductor

RLC Series Circuits

A circuit containing a capacitor, inductor, and resitor in series.

Direct Current (DC)

The flow of electric charge in only one direction, the steady state of a circuit with a constant voltage source, such as a battery.

Alternating Current (AC)

The flow of electric charge that periodically reverses direction; produced by an alternating emf that is generated in a power plant.

Resonance in an AC Circuit

occurs when the inductive and capacitive reactances are equal in magnitude, resulting in maximum current and power transfer at the resonant frequency.