2025-2026 Science Resource Guide: Electricity, Magnetism, and Electromagnetic Waves (Jordan High School)

Introduction

The document is a 2025–2026 Science Resource Guide created for Jordan High School, Katy, TX, focusing on electricity and magnetism during the Roaring Twenties as a gateway to understanding modern electromagnetism. It traces a historical arc from early observations of electrical phenomena to the unification of electricity and magnetism, culminating in electromagnetic waves and relativity. The Introduction emphasizes how electricity transformed homes, industry, and communications in the 1920s, with statistics such as: at the start of the 1920s about one in three US homes had electricity, rising to roughly seventy percent by the end of the decade; electrification expanded power tools, lighting, and household appliances; radios spread after 1923 and later versions plugged into outlets; electrification boosted manufacturing electrification from about 30% (1914) to ~70% by 1929. The Guide promises a journey through fundamentals (foundations of electricity, atomic particles, and forces) to circuits, magnetism, and electromagnetism, and finally to electromagnetic waves and relativity. The text reminds readers that many bold terms are defined in the glossary or units appendix. The historical narrative emphasizes the idea that electricity is not a single substance but a collection of phenomena unified by a fundamental force and field concepts.

Section I: Electricity

Charged Particles

A Brief History of the Atom. For millennia, people observed that rubbing certain materials could attract small lightweight objects, a phenomenon originally called the electric force by William Gilbert (1544–1603). The term derives from the Greek elektron for amber. Over centuries, philosophers debated the fundamental nature of matter, moving from the four classical elements toward the modern atomic view. The Periodic Table organizes atoms by type, each element defined by its proton count. Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons. The Greek word atom means indivisible, but atoms are ultimately not indivisible; the modern view accepts substructure, though atoms are still treated as fundamental units for many explanations. The nucleus contains protons and neutrons; electrons orbit the nucleus. Hydrogen has 1 proton and typically 1 electron; oxygen has 8 protons and 8 electrons. Atoms are overall neutral because the number of protons equals the number of electrons. Mass is a fundamental quantity measured in kilograms; electrons have very small masses compared to protons and neutrons. Protons carry a positive charge and electrons a negative charge of equal magnitude. Neutrons are electrically neutral. The text emphasizes that electricity concerns the movement of electrons rather than protons; protons are much heavier, so inside atoms the lighter electrons move most readily when charges rearrange. The idea of charge conservation (electric charge cannot be created or destroyed, only transferred) is introduced via Franklin’s experiments. The Earth-Sun analogy is used to explain inertial frames and Newton’s laws of motion: a force causes acceleration proportional to the force and inversely proportional to mass; action-reaction pairs obey Newton’s third law; the nucleus remains relatively stationary due to the much larger mass of protons compared to electrons. The section stresses that the proton is treated as a fundamental particle for the purposes of this guide, while quarks exist inside protons and neutrons but are neglected in introductory explanations of electricity. The conceptual framework emphasizes that science models are approximations: electrons are treated as fundamental particles to match observations in electricity and common atomic interactions.

Electrons and Protons. The text explains the structure of an atom: nucleus with protons and neutrons; electrons orbiting outside the nucleus. The mass and charge of the proton are significantly larger than those of the electron (roughly 1,800× more massive for the proton). The charges are equal in magnitude and opposite in sign: +e for protons and −e for electrons, with e ≈ 1.7 × 10^−19 C. The movement of electrons is the primary source of electrical phenomena; neutrons are electrically neutral and do not participate in electricity. The movement and arrangement of charges give rise to electric forces between objects, with opposite charges attracting and like charges repelling. The text uses a planetary model analogy and Newton’s laws to explain why electrons stay in orbit and why electrons move more readily than protons. The idea of charge quantization is introduced: charge comes in discrete units of ±1.7 × 10^−19 C. The Coulomb constant k is explained as roughly 8.99 × 10^9 N m^2/C^2, and the gravitational force is introduced as a comparison: FG = G m1 m2 / r^2 with G ≈ 6.67 × 10^−11 N m^2/kg^2. A key point is that electric forces dominate at atomic scales, whereas gravity dominates at astronomical scales due to the relative strengths (electric forces are far stronger between charged particles, on the order of 10^40 for a pair of electrons or protons). The Importance of charge conservation and the concept that total charge in the universe is zero are emphasized.

Two fundamental ideas are highlighted: (1) the electrical force is a central, inverse-square law dependent on charge, and (2) fields provide a framework to calculate forces on charges without tracking every particle. The text also introduces the notion of polarities: same charges repel; opposite charges attract; protons have positive charge, electrons negative, and neutrons zero. It discusses the electron’s orbital motion and Newtonian analogies for inertia, and emphasizes that models approximate reality but can accurately predict phenomena in many situations.

Electric Forces and Coulomb’s Law. The text introduces Coulomb’s Law: FE = \frac{k q1 q_2}{r^2} where q1 and q2 are the charges, r is the distance between charges, and k is the Coulomb constant (k ≈ 8.99 × 10^9 N m^2/C^2). The charges on protons and electrons are ±e, with e ≈ 1.7 × 10^−19 C. Since charges come in discrete units, charge is quantized; large objects accrue net charge by adding or removing electrons. Charge conservation means the total charge of a closed system remains fixed; positive and negative charges balance to yield a net neutral system often. The guide notes that the magnitude of the electric force can vastly exceed gravity for charged particles, explaining why gravity dominates at large scales while electricity dominates at atomic and molecular scales. The text uses examples like rubbing cloth with glass to illustrate the transfer of electrons, the idea of charge transfer, and the concept that heating or charging effects can occur on neutral objects due to polarization.

Electric Fields. The text introduces the concept of a field: a region of space where a charge experiences a force. An electric field E describes the force on a test charge q via F_E = qE, or equivalently, the field at distance r from a point charge is E = \frac{k q}{r^2}. Positive charges create outward electric fields, while negative charges create inward fields. The field is a vector field; it has magnitude and direction, pointing away from positive charges and toward negative charges. The idea of field lines helps visualize the interaction between charges. The field for an extended object can be calculated by summing contributions from all charges or by using symmetry to simplify calculations (as in Gauss’s law, described next). The text emphasizes adding fields from multiple charges is valid because fields superpose, and that far away from charges, the field resembles that of a single combined charge. In the interlude on fields, the author introduces the notion of the electric field created by individual charges and how a second charge experiences a force due to the field of the first.

Symmetry and Gauss’s Law. The Guide introduces symmetry as a powerful tool to simplify field calculations. It presents Gauss’s law in its integral form: \PhiE = \ointS \mathbf{E} \cdot d\mathbf{A} = \frac{q{ ext{enc}}}{\varepsilon0}, where (\varepsilon0) is the permittivity of free space with the relation \varepsilon0 = \frac{1}{4\pi k}.

The text illustrates the use of a Gaussian surface (a closed surface) to compute electric flux for simplified charge distributions, such as a uniformly charged sheet: for an infinite sheet, the electric field is uniform and perpendicular to the sheet, giving E = \frac{\sigma}{2\varepsilon_0}, where (\sigma) is the surface charge density (C/m^2). The sheet yields a flux through the Gaussian surface that is independent of the distance from the sheet, a consequence of the symmetry. The concept of flux through a surface is discussed conceptually as the amount of field that passes through the surface and is dependent on field strength and orientation. The section emphasizes the power of symmetry to avoid calculating the field from each particle individually.

Electric Fields in Materials and Polarization. The Guide discusses the behavior of fields in materials: static electricity arises from charge separation; some materials tend to become positively charged while others gain electrons. The Van de Graaff generator is given as an example of static electricity producing surface charges; contact with a charged surface transfers charge and can result in notable effects (e.g., hair standing on end). Electric polarization is introduced as the shift of charges within a neutral atom or molecule in response to an external electric field: electrons are displaced relative to the nucleus, leading to a slight polarity and an attractive net force. Water molecules are polar and align with external fields, contributing to the “stickiness” of water and its role in washing and surface interactions. Conductors vs Insulators: conductors allow charge to flow freely due to loosely bound outer electrons, whereas insulators resist charge movement. The text notes practical devices like Faraday cages where interior fields are shielded by conductor geometries. In conductors, charges arrange to cancel interior fields, so the electric field inside a conductor is zero in electrostatic equilibrium. The guide also notes that corners tend to have higher charge density, which is crucial for understanding lightning rods.

Section I Summary. The major points summarized include: elements on the Periodic Table are atoms with protons, neutrons, and electrons; protons and electrons carry equal and opposite charges; atoms are overall neutral; protons and electrons have very different masses; the electric force is Coulomb’s law and is an inverse-square force with charges; all charged objects produce an electric field; extended objects can be analyzed via symmetry; static electricity arises from charge separation and is influenced by polarization; conductors and insulators behave differently with respect to charge movement. The section emphasizes the predominance of electrons in electricity, the role of the electric field, and Gauss’s law as a tool for simplifying problems.

Section II: Circuits

Energy, Kinetic and Potential. The guide traces the concept of energy as the capacity to do work and its conservation in closed systems: energy transforms between kinetic energy (energy of motion) and potential energy (energy of position). An example is Joule’s experiments linking work and heat, underpinning the thermodynamics that drive electricity-powered devices. The text emphasizes that energy is conserved in all processes, and that energy changes form through various pathways. The relation between heat and temperature is introduced; temperature describes the average kinetic energy of atoms; heat is energy in transit between objects at different temperatures. The second law of thermodynamics states that heat flows from higher temperature to lower temperature when systems come into contact. The pendulum example shows energy exchange between kinetic and gravitational potential energy, with total energy conserved in the absence of dissipative forces. The text also introduces gravitational potential energy as an analogy to electric potential energy.

Voltage, Electric Potential, and Electric Potential Energy. The Guide discusses voltage as the difference in electric potential between two points, measured in volts (V). Electric potential energy is proportional to the charge, while electric potential (voltage) is energy per unit charge. Voltage is the potential difference between two points and can drive current if a path exists for charges to move. The relation between voltage and the electric field is often conceptualized: high potential differences create “electric pressure” that can drive current if a conducting path exists. The text uses a topographic map analogy with equipotential lines: a line represents equal potential; crossing lines converts potential difference to kinetic energy via the relation ∆E = qV, where q is the charge and V is the potential difference. The energy change equals the work done by the electric forces as the charge moves across the potential difference. The document introduces the concept that voltage is measurable (via voltmeters) and is a property of the environment, not of a single point. Capacitive energy storage uses equipotential differences as a concept to describe how energy can be stored in capacitors.

Batteries. The origin of the battery is traced to Volta’s experiments with two metals in an acidic solution, generating a voltage; the Galvanis’ frog experiments inspired discussions about life force and galvanism; Volta’s pile produced up to about 30 V in early experiments. Modern batteries maintain a constant voltage by keeping positive and negative charges separated; disposable (primary) cells use zinc and carbon in acid; secondary (rechargeable) cells such as lithium-ion batteries move ions back and forth; charging generates heat (inevitable energy loss). The battery’s terminals become the places where the external circuit connects; the electrolyte and metals are critical to maintaining charge separation. The role of environmental and ethical implications (e.g., mining for lithium) is acknowledged as a practical factor in contemporary energy systems. The text also discusses a lemon-and-metal battery as a simple demonstration of producing a small voltage.

Simple Circuits and a Fluid Model. The circuit is described using a water-pipe analogy: a pump supplies water creating high pressure and a flow through a closed loop. Energy transfer is illustrated via a battery pushing charges through a wire; current is a flow of charges, not motion of the charges themselves; the battery maintains a potential difference across the circuit, allowing current to flow. The flow of charge is likened to a domino effect: energy is transferred quickly along the path, while individual charges move slowly but energy propagates at nearly the speed of light due to field interactions. A key nuance: the electrons in a wire drift very slowly, but the signal for current propagates quickly through the electric field. The text also distinguishes the conventional flow direction (positive current) from the actual electron flow direction (opposite to the conventional current). The concept of ground and safety is introduced: grounding provides safe pathways for current to prevent dangerous paths through a person.

Ohm’s Law and Power. Ohm’s law relates current I, voltage V, and resistance R: I = \frac{V}{R}. Power is defined as the rate of energy transfer: P = IV. The guide explains how power and energy relate, such as a 100-watt light bulb, where a given voltage and resistance produce a certain current; power dissipates as heat in resistive components. The text discusses the safety implications of high voltages and currents: high voltage doesn’t always mean dangerous energy if the current path is controlled; a fork in a wall socket may deliver dangerous current due to conductive paths. The role of grounding, fuses, and circuit breakers in preventing fires from high currents is explained. A practical connection is made to energy bills: kilowatt-hours (kWh) are a measure of energy, where one kWh equals 3.6 × 10^6 joules. The text also mentions that electrons drift slowly, but energy transmission is rapid due to electromagnetic signaling along the circuit.

More Complicated Circuits: The Path of Least Resistance. The guide covers series and parallel resistor configurations. In series, current is the same through all elements and total resistance is the sum: $$R{ ext{total}} = R1 + R2 + R3 + \,.\