Physics › Equations › Capacitance

Capacitance equations

The 9 equations the capacitance notes display, each with a link to the lesson that states it. Of the 9, the data booklet prints 5, 1 is yours to memorise and 3 carry no badge either way.

Year 13 · 3 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.

3 lessons

Capacitors and the dielectric

C = \frac{Q}{V}

IN THE AQA DATA BOOKLET

C = 4\piε_{0}r

C = \frac{Aε_{0}ε_{r}}{d}

IN THE AQA DATA BOOKLET

Energy stored and capacitor combinations

E = \frac{1}{2}QV = \frac{1}{2}CV^{2} = \frac{1}{2}\frac{Q^{2}}{C}

IN THE AQA DATA BOOKLET

C = C_{1} + C_{2} + \ldots

\frac{1}{C} = \frac{1}{C_{1}} + \frac{1}{C_{2}} + \ldots

The time constant and exponential decay

T_{½} = 0.69RC

NOT IN THE AQA DATA BOOKLET: LEARN IT

Q = Q_{0}e^{-t/RC}

IN THE AQA DATA BOOKLET

Q = Q_{0}(1 - e^{-t/RC})

IN THE AQA DATA BOOKLET

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

Also: Electric fields equations · Magnetic fields equations