Physics › Equations › Electricity

Electricity equations

The 14 equations the electricity notes display, each with a link to the lesson that states it. Of the 14, the data booklet prints 9, 2 are yours to memorise and 3 carry no badge either way.

Year 12 · 7 lessons with equations.

The marks refer to the AQA 7408 data booklet. An equation it prints is marked as such, and one it leaves out is marked to learn. An equation with no mark has not been checked against that booklet, and some of these belong to the Edexcel, OCR or CIE specification rather than AQA’s, so check them against your own board’s data or formula booklet.

7 lessons

Current, charge and potential difference

I = \frac{\Delta Q}{\Delta t}

IN THE AQA DATA BOOKLET

V = \frac{W}{Q}

IN THE AQA DATA BOOKLET

Charge carriers, drift speed and resistance

I = nAvq

R = \frac{V}{I}

IN THE AQA DATA BOOKLET

Resistivity and temperature

\rho = \frac{RA}{L}

IN THE AQA DATA BOOKLET

Series, parallel and power

R_{T} = R_{1} + R_{2} + R_{3} + \ldots

IN THE AQA DATA BOOKLET

\frac{1}{R_{T}} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{3}} + \ldots

IN THE AQA DATA BOOKLET

E = IVt

NOT IN THE AQA DATA BOOKLET: LEARN IT

P = IV = I^{2}R = \frac{V^{2}}{R}

IN THE AQA DATA BOOKLET

The potential divider and its output

V_{out} = V_{in} \times \frac{R_{2}}{R_{1} + R_{2}}

NOT IN THE AQA DATA BOOKLET: LEARN IT

Unloaded divider: the output must supply negligible current.

V_{x} = V\frac{x}{L}

Sensing circuits and the potentiometer

\frac{E_{1}}{E_{2}} = \frac{l_{1}}{l_{2}}

EMF and internal resistance

\epsilon = \frac{E}{Q}

IN THE AQA DATA BOOKLET

\epsilon = I(R + r)

IN THE AQA DATA BOOKLET

Every equation in the library is indexed by unit on the equation index, and the electricity notes are where these equations are derived and used. The 2 the booklet leaves out are on the equations to memorise, alongside the rest of the course.

Also: Particles equations · Periodic motion equations