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Electricity & Magnetism · Physics

Magnetism links forces, motion, and induction.

Build from magnetic fields and forces to induction, circuits with inductors, AC ideas, and a conceptual Maxwell unification.

Magnetism track

Topics

Each topic is a set of nano-lessons designed for fast mastery and clean conceptual understanding.

15
Magnetic Fields
Define the magnetic field and interpret field lines, sources, and key differences from electric fields.
  • Magnetic field definition
  • Magnetic field lines
  • Sources of magnetic fields
  • Comparison with electric fields
Start topic Start with B and what it does.
16
Magnetic Forces on Charges and Currents
Use the Lorentz force and the force on a current-carrying wire. Apply right-hand rules and interpret motors.
  • Lorentz force on moving charges
  • Force on a current-carrying wire
  • Right-hand rules
  • Applications to motors
Start topic Direction is the whole story.
17
Motion of Charged Particles in Magnetic Fields
Predict circular and helical motion, interpret cyclotron frequency, and understand velocity selectors conceptually.
  • Circular motion of charged particles
  • Helical motion
  • Cyclotron frequency
  • Velocity selectors (conceptual)
Start topic B changes direction, not speed.
18
Magnetic Fields Produced by Currents
Learn the magnetic field patterns for wires, loops, solenoids, and toroids using symmetry and field-line reasoning.
  • Field around straight wires
  • Field of loops
  • Solenoids and toroids
Start topic Currents create circulation in B.
19
Biot–Savart Law
Use the Biot–Savart law to compute magnetic fields from current elements and compare it to Ampère’s law.
  • Mathematical statement
  • Simple current geometries
  • Comparison with Ampère’s law
Start topic Field from current elements.
20
Ampère’s Law
Apply Ampère’s law with symmetry to compute magnetic fields for solenoids and toroids using current loops.
  • Statement of Ampère’s law
  • Symmetry and current loops
  • Applications: solenoids and toroids
Start topic Use when symmetry is strong.
21
Magnetic Flux
Define magnetic flux through a surface and build intuition for “how much field passes through” an area.
  • Definition of magnetic flux
  • Flux through surfaces
  • Changing flux concepts
Start topic Flux is dot product intuition.
22
Faraday’s Law of Electromagnetic Induction
Relate changing magnetic flux to induced emf and connect the idea to generators and time-varying fields.
  • Induced emf
  • Time-varying magnetic fields
  • Applications: generators
Start topic Changing flux drives emf.
23
Lenz’s Law
Determine the direction of induced current and interpret the minus sign in Faraday’s law as energy conservation.
  • Direction of induced current
  • Energy conservation interpretation
  • Common sign-convention errors
Start topic Induced effects oppose change.
24
Inductance
Learn self-inductance, mutual inductance (intro), and how energy is stored in magnetic fields.
  • Self-inductance
  • Mutual inductance (intro)
  • Energy stored in magnetic fields
Start topic Inductors resist current change.
25
RL Circuits
Analyze current growth and decay with inductors, interpret the time constant, and track energy transfer.
  • Current growth and decay
  • Time constant
  • Energy transfer in inductors
Start topic RL is the magnetic analog of RC.
26
AC Circuits
Introduce alternating current, RMS values, and the qualitative meaning of reactance and impedance.
  • Alternating current and emf
  • RMS values
  • Reactance and impedance (qualitative)
Start topic AC adds phase and frequency.
27
Maxwell’s Equations
A conceptual overview of the four Maxwell equations and how they unify electricity, magnetism, and electromagnetic waves.
  • Unification of electricity and magnetism
  • Meaning of each equation
  • Electromagnetic waves (conceptual link)
Start topic Big picture, clean meaning.
Practice
Practice & Exercises
Mixed practice across magnetic forces, fields from currents, induction, and time-dependent circuits.
  • Direction + right-hand-rule drills
  • Compute B for symmetric current geometries
  • Flux and induced emf sign practice
  • RL transient concept checks
  • Exam-style magnetism mixed sets
Open practice Prioritize direction and sign.