1.9 Sources

Outcome 9 of 9 in domain 1 · Foundations, direct current

Primary cells, rechargeable cells, power supplies; internal resistance, drop under load.

My targets

I declare:

Explain a source’s internal resistance and measure it on a cell (open-circuit voltage, voltage under a known load).
Predict a pack’s voltage drop under a given load, then measure it.
Read a power supply’s characteristics (voltage, max current, regulation) and know what it does when you exceed them.
Put two sources in series and in parallel, say when it’s allowed and what happens when they differ.
Compare primary cells and rechargeable cells (alkaline, NiMH, lead, lithium): voltage, curve, self-discharge, and choose for a given use.
Diagnosis: a tool that stops under load while the pack reads full, internal resistance, weak cell or BMS; the measurement path to decide.