COS- Exam 2

Properties of Charges

Charges attract or repel, can move, and produce electric fields

Electric Field

The region around a charge where its influence can be felt; field lines have direction and add together for multiple charges

Positive Charge

Found on protons

Negative Charge

Found on electrons

Magnet

An object with two poles (N and S) that produces a magnetic field

Magnetic Poles

Always exist in pairs; like poles repel, opposite poles attract

Magnetic Monopole

A hypothetical magnetic pole that has never been observed

Magnetic Field

The region around a magnet where its influence can be felt; lines go from N to S

Electric vs Magnetic Fields

Electric fields can exist as monopoles; magnetic fields are always dipoles; both are directional

Earth's Magnetic Field

Geographic North Pole is actually a magnetic south pole; field can flip over thousands of years

Auroras

Produced when charged particles from the sun follow Earth's magnetic field into the atmosphere and react with gases

Clicker Question: Magnet Cutting

A bar magnet cut multiple times produces a dipole in each piece; final number of N poles = 4

Electric Current

Flow of moving electric charges

Circuit

A complete path that allows current to flow

Voltage

The “reason” charges move; measured in volts; analogous to water pressure

Resistance

Property of a material that opposes current; measured in ohms (Ω)

Ohm's Law

Relationship between voltage, current, and resistance: V = I * R

Current

Flow of electrons; measured in amperes (amps)

Closed Circuit

Required for current to flow; must form a complete loop

High Voltage Safety

Exposure to high voltage is relatively safer if the resistance of the object is very high

Water Analogy for Circuits

Voltage = water pressure, current = water flow, resistance = pipe constriction, circuit = closed pipe

Electromagnet

Electric current through a coil produces a magnetic field

Electric Motor

Uses interaction between permanent magnet and electromagnet to produce motion

Electromagnetism

The study of electricity and magnetism as interconnected phenomena

Electromagnetic Induction

Moving a magnet near a wire induces a current in the wire (reverse of motor principle)

Electric Charge

All electrical phenomena arise from charges; two types exist: positive (+) on protons, negative (

Coulomb's Law

Describes the force between two charges: FE = k q1q2 / d^2

Wave

A transfer of energy without a transfer of matter

Radiation

For our purposes, radiation is considered as waves; some historical uses of the term are not strictly accurate

Vibration (Oscillation)

The starting phenomenon of all waves; the source of wave energy

Propagation

The travel of a wave through a medium

Direction of Propagation

The direction in which a wave moves

Medium

The material through which a wave propagates, transferring vibrations from the source

Longitudinal Wave

A wave in which vibrations are parallel to the direction of propagation

Transverse Wave

A wave in which vibrations are perpendicular to the direction of propagation

Sound Waves

A common type of wave; a longitudinal wave traveling through a medium

Other Wave Examples

Water waves, seismic waves, light waves

Amplitude

The maximum distance traveled by the vibrating medium, measured from the midpoint

Wavelength

The physical distance between two corresponding points on adjacent cycles of a wave

Crests and Troughs

The high and low points of a wave where amplitude is measured

Frequency

The number of cycles a wave makes every second; higher frequency means the source vibrates faster and has higher kinetic energy

Frequency

Energy Relationship

Wavelength Units

Symbol λ, units meters (m); the distance between two corresponding points on adjacent cycles

Frequency Units

Symbol f, units 1/seconds or Hertz (Hz)

Clicker Question: Units of λf

If wavelength (λ) is in meters and frequency (f) in Hz, their product λf has units of m/s

Clicker Question: Wave Production Requirement

For a wave to be produced, vibration is necessary

Electromagnetic Waves

Waves consisting of oscillating electric and magnetic fields

EM Wave Orientation

Electric and magnetic fields are perpendicular to each other and perpendicular to the direction of propagation

EM Waves Type

Transverse waves

Electromagnetic Spectrum

The range of all electromagnetic waves ordered by frequency or wavelength; higher frequency means higher energy

Wavelength

Frequency Relationship

Speed of Electromagnetic Waves

Electromagnetic waves travel at a constant speed of 3.0 × 10^8 m/s, denoted as c

Democritus’ Atomic Theory

Proposed that atoms (atomos) are small, hard particles, always in motion, capable of joining together, and made of the same material

Existence of Atoms

Confirmed in the 1800s through scientific experiments

Dmitri Mendeleev

Created the periodic table in 1869, classifying elements by properties

Subatomic Particles

Atoms are made of electrons (negative), protons (positive), and neutrons (neutral)

Mass of Subatomic Particles

Protons and neutrons have approximately the same mass, about 1800 times the mass of an electron

Elemental Symbol

The letter(s) used to represent an element, often derived from Latin (e.g., Au for gold, from aurum)

Atomic Number

The number of protons in an atom; usually equals the number of electrons, though this can change

Atomic Mass (Weight)

The average mass of an atom in atomic mass units (AMU); roughly protons + neutrons + electrons

Ion

An atom that has lost or gained electrons, giving it a negative or positive charge

Isotope

Atoms of the same element with different numbers of neutrons

Changing Protons

All atoms of the same element have the same number of protons; gaining or losing a proton changes the element (nuclear reactions)

Periodic Table Arrangement

Elements are arranged by increasing atomic number from left to right, top to bottom

Column Properties

Atoms in the same column have similar chemical properties

Salts

Compounds formed when elements from column 2 combine with elements from column 17

Noble Gases

Elements in column 18 that are very unreactive due to their full electron shells

Synthetic/Heavy Elements

Many heavy elements do not occur naturally and are created in laboratories; they are highly unstable and decay quickly

Clicker Question: Element with 8 Protons

The element with 8 protons is Oxygen

Clicker Question: Safer Dirigible Gas

Helium is the safer choice for filling a blimp compared to hydrogen

Clicker Question: Titanium Atomic Number

Titanium has an atomic number of 22, meaning it always has 22 protons

Atomic Nucleus

The majority of an atom’s mass is in the nucleus, which contains protons and neutrons

Electron Cloud

Electrons are found outside the nucleus in the electron cloud, not orbiting like planets

Electron (Energy) Shells

Electrons exist in energy shells; each shell can hold a specific number of electrons and has a specific energy level

Strong Nuclear Force

The force that holds the protons and neutrons together in the nucleus, overcoming electrical repulsion

Empty Space in Atoms

Atoms are almost completely empty space, with most mass concentrated in the nucleus

Electron Shell Capacity

Each electron shell can hold a specific number of electrons, affecting how atoms interact chemically

Hydrogen Electron Configuration

Hydrogen has one electron; its inner shell can hold two

Oxygen Electron Configuration

Oxygen has six electrons in its second shell, which can hold up to eight

Covalent Bond

A chemical bond formed when atoms share electrons to fill their outer shells

Valence Shell

The outermost electron shell; if full, the atom is chemically inert (as in noble gases)

Subshells

Each electron shell is divided into subshells, each holding a specific number of electrons; total electrons in subshells cannot exceed shell maximum

K and L Shells

The K shell has one subshell holding 2 electrons; the L shell has two subshells holding 2 and 6 electrons respectively, for a total of 8

Electron Energy Levels

Electrons in subshells have exact energy amounts, allowing transitions between levels by absorbing or releasing energy equal to the difference

Photon

A packet of energy; light can be considered both a wave and a particle, with its frequency corresponding to its energy and color (if visible)

Excited State

When an electron occupies a high

Electron Transition

When an electron falls from a higher energy subshell to a lower one, it must release a specific amount of energy

Photon Emission

The energy released by an electron dropping to a lower energy level is emitted as a photon (light)

Subshell Representation

Horizontal lines are used to represent energy subshells in diagrams

Multiple Transitions

In a sample, trillions of electrons transition every second, producing many photons of different energies

Spectroscopy

The study of the light emitted by electron transitions to analyze the composition of substances

Atom

The smallest unit of a substance that retains its chemical properties; composed of protons, neutrons, and electrons

Proton

Positively charged particle found in the nucleus of an atom

Electron

Negatively charged particle found outside the nucleus in the electron cloud

Neutron

Neutral particle found in the nucleus of an atom

Atomic Number

Number of protons in an atom; also generally equals the number of electrons in a neutral atom

Atomic Mass

Average mass of an atom of an element, expressed in atomic mass units (AMU)

Isotope

Atoms of the same element with different numbers of neutrons

Ion

An atom that has gained or lost electrons, resulting in a net charge

Electron Cloud

Region outside the nucleus where electrons are likely to be found