# Inductance for MCU / DC Electronics — Glossary

The canonical language for this workspace: coils, transients, and the components that
control them. Every lesson and reference sheet uses these words in these senses.

**A term is added here only once Charlie can use it correctly** — not when it is first
introduced. The glossary is a record of compressed understanding, not a preview.

## Terms

_Empty — Lesson 01 introduced the candidates below, but nothing has been promoted yet._

## Candidates awaiting evidence

Introduced in [Lesson 01](./lessons/0001-the-current-flywheel.html); promote once used
correctly in conversation or an exercise.

- **Inductance** — a coil's opposition to a *change* in current, in henries.
  _Avoid_: coil strength, magnetic resistance
- **Flyback diode** — a diode across an inductive load that gives the coil's current a
  path to circulate in at turn-off. _Avoid_: snubber diode, back-EMF diode, kickback diode
  (all in circulation; pick one and stick to it)
- **Clamp voltage** — the voltage the switch node is held at while the coil's current
  decays. The single variable that sets the speed/stress trade-off.
- **Switch node** — the junction between the load and the switching device. Where the
  transient appears and where it is measured.
- **Turn-off transient** — the voltage excursion at the switch node when current in an
  inductive load is interrupted. _Avoid_: back-EMF (means something different and more
  specific in motors — reserve it), kickback, spike

## Ambiguities to resolve

- **"Back-EMF"** is used loosely in hobby sources for two unrelated things: the turn-off
  transient of any coil, and the speed-proportional voltage a spinning motor generates.
  In this workspace, **back-EMF means only the motor's speed voltage**; the switching
  event is always the **turn-off transient**.
- **"Snubber"** in this workspace means specifically an **RC** network. Diodes, zeners and
  TVS devices are **clamps**, not snubbers.