Every fact in the three electricity lessons is listed here with where it comes from. The numbers in [brackets] on the lesson pages link to this list.
How we rate sources
High: space agencies (NASA), peer-reviewed open textbooks (OpenStax, Rice University) and professional scientific societies (American Physical Society).
Medium-high: reputable science news reporting directly on a primary document.
Medium: single-author essays and popular history sites. We only use these for history details, and never on their own: each one is paired with a second source.
Wikipedia was not used as a source. Numbers are rounded (for example 9.8 m/s² for Earth's gravity). The text was drafted with help from AI (Claude) and then checked against these sources. Corrections: hello@echoesof.science.
Simplifications to be aware of: the younger lessons describe current as electricity 'flowing round' a circuit. In metal wires it is really electrons that move, in the opposite direction to the 'conventional current' used in circuit diagrams. Ohm's law holds for ohmic conductors such as metal wires at constant temperature; a filament lamp's resistance rises as it heats up. All experiments use 1.5–6 V batteries only.
All sources
[1] College Physics 2e AP, 20.1 Current
OpenStax, Rice University · Reliability: High
Type: Peer-reviewed open textbook
Defines current as the rate of flow of charge, I = ΔQ/Δt, with 1 A = 1 C/s; conventional current is the direction positive charge would flow, while in metal wires electrons carry the current in the opposite direction; a steady current needs a continuous energy input, for example from a battery driving current round a closed loop.
[2] College Physics 2e, 20.2 Ohm's Law: Resistance and Simple Circuits
OpenStax, Rice University · Reliability: High
Type: Peer-reviewed open textbook
Gives Ohm's law V = I·R (I = V/R), the ohm (1 Ω = 1 V/A), ohmic materials such as copper and aluminium, and a simple circuit as a voltage source and a resistor joined by conductors in a closed path.
[3] College Physics 2e, 21.1 Resistors in Series and Parallel
OpenStax, Rice University · Reliability: High
Type: Peer-reviewed open textbook
In series, resistances add (Rs = R1 + R2 + …) and the same current flows through each; in parallel, 1/Rp = 1/R1 + 1/R2 + …, each branch gets the full source voltage, and household devices are wired in parallel so each works independently.
[5] College Physics 2e AP, 18.2 Conductors and Insulators
OpenStax, Rice University · Reliability: High
Type: Peer-reviewed open textbook
Conductors such as metals have free electrons that let charge move easily; insulators such as glass, rubber and plastic hold their charges in place, which is why plastic and rubber cover the wires in cables.
[6] Using electricity safely (Power Up, under-11s)
UK Power Networks (electricity network operator) · Reliability: Medium-high
Type: Electricity company education programme
Safety rules for children: never poke fingers or anything else into sockets or appliances; keep electrical appliances away from water; never touch them with wet hands; never climb into substations; never fly a kite near an overhead line.