Use current-made magnetic fields, changing flux, Maxwell's four-law synthesis, magnetic force, and field-pair propagation without turning the branch into a detached rule list.
Use this page when the voltage-and-current story is already stable and you want the magnetic branch to stay coherent. The overview starts with magnetic fields built by current, then keeps that same B-field picture honest in four directions: changing flux linkage creating Faraday/Lenz induction, an existing magnetic field pushing on moving charges or current segments, a compact Maxwell synthesis that keeps source laws and circulation laws in one picture, and the propagation case where changing electric and magnetic fields travel together and later bridge into optics.
Best first concepts
The topic page keeps these starts in their own compact row so the first screen is about orientation and next action, not stacked feature cards.
See how current direction, wire spacing, distance, and superposition set the magnetic field around one or two long straight wires, with the stage arrows and scan graphs tied to the same live source pattern.
Fields around current
Strong first stop for getting into this topic without scanning the whole library.
See what each Maxwell equation says physically, how sources and circulation differ, and why changing electric and magnetic fields together unify electricity, magnetism, and light.
Field synthesis
Strong first stop for getting into this topic without scanning the whole library.
Specific learning goals
These goal cards stay authored and transparent. They reuse the current topic page, starter tracks, guided collections, concept bundles, and progress cues instead of adding a separate recommendation system on top of this branch.
Use the electricity route, the existing electricity-to-magnetism bridge collection, and the magnetic starter track so the transition into electromagnetism stays bounded and transparent.
Primary move
Start Electricity
Electricity is the authored prerequisite for Magnetism. Electric Fields opens this track and sets up the rest of the path. Nothing is hard-gated here; this is simply the authored prep path.
Entry diagnostic
Start from the opening step
No saved diagnostic checks are available yet, so the opening step is still the best entry into the collection.
Reuses the guided collection entry for Electricity to Magnetism Bridge, with 0 of 2 probes already ready.
Recommended prep
Electricity is the authored prerequisite for Magnetism. Electric Fields opens this track and sets up the rest of the path.
No saved progress yet inside Electricity.
Reopen the electricity track in recap mode is the next guided collection step.
Magnetic Fields opens this track and sets up the rest of the path.
No saved progress yet for Maxwell's Equations Synthesis.
Grouped concept overview
Each group is authored in the topic catalog, but the actual concepts, progress badges, and track cues still come from the canonical concept metadata and shared progress model.
Group 01
Start with the circular magnetic pattern around current-carrying wires so the right-hand-rule story is attached to one live source before anything changes in time.
看電流方向、導線間距、距離與疊加如何決定一到兩條長直導線周圍的磁場，讓舞台箭頭與掃描圖都綁在同一個即時來源配置上。
Strong first stop for getting into this topic without scanning the whole library.
Group 02
Once the field direction is trustworthy, use it two ways: changing flux linkage to create induced emf, and a steady field to bend moving charges or push a current segment.
讓一個運動電荷穿過均勻磁場，再與同方向電流段比較，並在同一個受限即時舞台上連結力的方向、軌跡彎曲與電流受力。
Group 03
Keep the source laws and circulation laws on one compact page before you ask the changing-field pair to support a light-like bridge.
理解每條馬克士威方程的物理意義、來源與環流的差別，以及為何電場與磁場的相互變化把電、磁與光統一起來。
Strong first stop for getting into this topic without scanning the whole library.
Group 04
After the synthesis page makes the changing-field handoff explicit, reuse that same pair in the propagation case where electric and magnetic fields travel together and point toward the optics branch.
看變化中的電場與磁場如何一起向右傳播成為同一個波，讓局部場對、源到探針的延遲與傳播線索都留在同一個小型即時舞台。