Matter, energy, fields, and forces
Build a physical vocabulary for what exists, what changes, and what carries influence.
Move from particles and atoms to energy accounting and fields, preparing for electromagnetism, nuclear physics, and vacuum-field ideas.
Before you begin
- • Course 1: Measurement, uncertainty, and evidence
- • Basic arithmetic
By the end, you can
- • Describe matter using atoms, charge, and mass.
- • Track energy transfers without treating energy as a material substance.
- • Use a field model to explain forces acting across space.
- • Apply conservation accounting to an unfamiliar device claim.
Interactive model
Explore before calculating
Live laboratory
Field-vector sandbox
Move a test point between two charges. Vector addition—not the nearest source alone—sets the local field direction and strength.
Local field: (0.51, 0.00) relative units; magnitude 0.51, direction 0.0°.
Level 1 · Foundations teaching kit
Record the investigation. Teach the reasoning.
A learner-facing lab record and a course-specific instructor guide turn the live model into a repeatable classroom investigation.
Learner record
Two-source field map
How do source sign, source strength, and observation position combine into one local field vector?
Download learner recordInstructor guide
Teach for evidence, not button pushing
Learners add field contributions as vectors and distinguish a field map from material lines in space.
Download instructor guideLesson 1 of 3
Atoms, mass, and charge
What common ingredients explain the enormous variety of ordinary matter?
Ordinary matter is built from atoms. Their nuclei contain protons and neutrons, while electrons occupy quantum states around the nucleus.
Mass and electric charge are different properties. Electric forces can attract or repel; gravity between classroom objects is far weaker but always attractive in ordinary situations.
Worked example
A neutral atom loses one electron. What changes?
- 1. The number of positive protons stays the same.
- 2. One negative electron is removed.
- 3. The charges no longer cancel.
The atom becomes a positively charged ion; its identity remains set by its proton count.
Try it
Static-charge investigation
Materials: A balloon or plastic comb and small paper pieces.
- 1. Bring the uncharged object near the paper.
- 2. Rub it on dry hair or cloth.
- 3. Repeat at several distances.
- 4. Record what changes and avoid naming a cause until after observing.
Notice: Charge separation creates a distance-dependent force that can move neutral paper by polarization.
Check your understanding: Which particle count determines which chemical element an atom is?
Answer: Its number of protons.
Changing electrons makes an ion; changing neutrons makes an isotope; changing protons changes the element.
Lesson 2 of 3
Energy is an accounting rule
Where did the ability to cause change come from, and where did it go?
Energy is a conserved quantity used to compare motion, position, heat, chemical change, radiation, and mass. It is not a mysterious fluid stored in only one form.
A device can transform energy and still waste much of it as heat. A complete claim states every input, useful output, stored change, and loss over a full cycle.
Worked example
A motor receives 100 J electrically, delivers 65 J of motion, and warms by 35 J.
- 1. Input: 100 J.
- 2. Useful mechanical output: 65 J.
- 3. Thermal output: 35 J.
- 4. Check the balance: 65 + 35 = 100 J.
The accounting closes and the useful efficiency is 65%. No energy disappeared.
Try it
Energy-chain map
Materials: Paper and a familiar device such as a flashlight or fan.
- 1. Draw the energy input.
- 2. Draw every useful output.
- 3. Add heat, sound, or other losses.
- 4. Mark any stored-energy change.
Notice: Naming the full chain prevents one impressive output from hiding a larger input.
Check your understanding: Can a machine be useful even when its efficiency is below 100%?
Answer: Yes.
Efficiency compares useful output with input; many valuable devices intentionally transform only part of the input into the desired form.
Lesson 3 of 3
Fields carry local instructions
How can an object respond to something that is not touching it?
A field assigns a value to each point in space and time. A charged particle responds to the electromagnetic field at its own location; a mass follows the local gravitational geometry.
Field diagrams are maps, not invisible strings. Their arrows or contours summarize what a suitable test object would experience.
Worked example
Why do field arrows around a positive charge point outward?
- 1. Define the direction using a small positive test charge.
- 2. Like charges repel.
- 3. The test charge would accelerate away from the source.
The outward arrows encode the force direction on a positive test charge.
Try it
Map a magnetic field
Materials: A bar magnet, paper, and a compass if available.
- 1. Place the magnet beneath the paper.
- 2. Sample compass direction on a grid.
- 3. Draw small arrows at each point.
- 4. Connect the pattern without implying material lines.
Notice: The local directions form a coherent map even though the compass only samples one point at a time.
Check your understanding: What does an electric-field arrow mean?
Answer: The direction a small positive test charge would be pushed at that location.
It is a local operational definition, not a claim that a visible arrow exists in space.
Continue into the evidence
Source-linked next reading
Chapter 3: The Zero-Point Field, Inertia, and Gravity
An advanced application of field thinking, clearly labeled by evidence status.
Lecture 3: General relativity
How mass-energy and geometry are connected in established theory.
Disciplinary spine
A map from established physics to open engineering claims.