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Electricity · Physics

From charge and fields to circuits and transients.

Build electrostatics first (charge, force, field, potential), then connect those ideas to capacitance, current, resistance, and circuit behavior.

This track

Electricity

Each topic is a set of nano-lessons designed for final-year high school and first-year university physics.

Topic 1
Electric Charge
Identify what electric charge is, how it is conserved, and how objects become charged.
  • Properties of charge
  • Conservation of charge
  • Conductors vs insulators
  • Contact and induction
Start topic Start with definitions and models.
Topic 2
Coulomb’s Law
Use Coulomb’s law as a vector force law and apply superposition to multiple charges.
  • Mathematical form
  • Vector nature of force
  • Superposition principle
  • Compare with gravity
Start topic Draw vectors before computing.
Topic 3
Electric Field
Treat the field as a mapping from space to force-per-charge, and compute fields from charge distributions (starting with point charges).
  • Definition of E
  • Field of a point charge
  • Superposition of fields
  • Meaning of field vectors
Start topic Think “force per unit charge.”
Topic 4
Electric Field Lines and Flux
Visualize fields with field lines and quantify “how much field passes through” a surface using flux.
  • Field line representation
  • Density and strength
  • Electric flux
  • Flat and curved surfaces
Start topic Flux needs area and orientation.
Topic 5
Gauss’s Law
Use symmetry to compute fields quickly by relating flux to enclosed charge.
  • Statement of Gauss’s law
  • Symmetry requirements
  • Gaussian surfaces
  • Spherical / cylindrical / planar cases
Start topic Symmetry is the whole game.
Topic 6
Electric Potential and Potential Energy
Move from forces to energy: define potential, relate it to work, and connect E and V.
  • Potential vs potential energy
  • Potential difference
  • Work by electric forces
  • Relationship between E and V
Start topic Energy methods simplify many problems.
Topic 7
Equipotential Surfaces
Understand equipotentials as constant-V surfaces and how they relate to field direction and strength.
  • Definition of equipotentials
  • Relation to field lines
  • Common charge distributions
  • Motion on equipotentials
Start topic E is perpendicular to equipotentials.
Topic 8
Capacitance
Model charge storage and voltage relationships for common capacitor geometries.
  • Definition of capacitance
  • Parallel-plate capacitors
  • Other geometries
  • Energy stored
Start topic C links Q and V.
Topic 9
Dielectrics
See how polarization changes fields, capacitance, and energy in capacitors.
  • Polarization
  • Dielectric constant
  • Effect on capacitance
  • Energy considerations
Start topic Materials reshape the field inside.
Topic 10
Electric Current
Connect macroscopic current to microscopic charge motion and current density.
  • Definition of current
  • Drift velocity
  • Microscopic view
  • Current density
Start topic Current is charge flow rate.
Topic 11
Resistance and Resistivity
Use Ohm’s law and material properties to model energy dissipation in circuits.
  • Ohm’s law
  • Resistivity and conductivity
  • Temperature dependence
  • Power dissipation
Start topic Separate material from geometry.
Topic 12
DC Circuits
Combine elements, compute equivalent resistance, and track energy and power in steady-state circuits.
  • Circuit elements
  • Series and parallel
  • Equivalent resistance
  • Energy and power
Start topic Reduce step-by-step.
Topic 13
Kirchhoff’s Laws
Apply junction and loop rules with consistent sign conventions to solve multi-loop networks.
  • Junction (current) rule
  • Loop (voltage) rule
  • Sign conventions
  • Multi-loop solving
Start topic Choose directions, then stay consistent.
Topic 14
RC Circuits
Model charging and discharging as exponential transients with a time constant.
  • Charging and discharging
  • Time constant
  • Exponential behavior
  • Energy flow in transients
Start topic τ = RC controls the time scale.
Practice
Practice & Exercises
Mixed practice across electricity topics, from electrostatics to circuits.
  • Charge, force, and field concept checks
  • Potential, flux, and Gauss’s law drills
  • Capacitance and dielectrics computations
  • DC circuit reductions and power questions
  • Kirchhoff and RC transient exam-style sets
Open practice sets Mix conceptual and computational work.