Reference sheet
Twelve formulas linking V, I, R and P
Twelve ways to get the four electrical quantities from any two you know. Find the quantity you want in the centre, then pick the outer formula built from what you have. P in watts, V in volts, I in amps, R in ohms.
The two everyone remembers: V = I×R and P = V×I — every other cell is those two rearranged.
AbbreviationsSMD, BOM, ESR, PTH: the jargon on datasheets and fab files
dBm powerDecibel-milliwatt to watts, and what each level means
ResistivityHow well common materials conduct
SI prefixesPico to giga, with the factors written out
Op-amp comparisonLM358, TL072, MCP6002 and co: supply, offset, speed
Oscilloscope basics1x vs 10x, compensation, triggering, aliasing
PCB design rulesTrace width and current, spacing, rings, drills, copper weight