Free printable
Printable electronics formula sheet
A one-page electronics formula sheet for students. It groups the formulas a beginner meets in their first year, from Ohm's law to LC resonance, with a short note on what each one gives.
One page. Free to print and share for teaching. Print at actual size (100%), not fit to page. A4 suits most of the world; US Letter suits the USA and Canada.
What's on the sheet
- Ohm's law and power, including the milliamps-and-kilohms shortcut
- Series and parallel resistors, capacitors and cells, and Kirchhoff's laws
- Dividers and LEDs: the voltage divider, the current divider and the LED resistor, with typical forward voltages
- Capacitors and inductors: charge, energy and the RC and RL time constants
- AC and filters: RMS, reactance, impedance, filter cutoff, resonance and decibels
- Transistors, op-amps, batteries and digital: gain, base resistor, battery life and PWM
- A key to every symbol, unit and prefix
How to use it in class
Give it out at the start of a course and ask students to keep it in their folder: they'll use it in nearly every practical. It also works as a revision checklist. Ask students to tick each formula they can explain, and to look up the ones they can't on the online formulas cheat sheet, which links each one to a guide.
Free lesson
Now build it yourself
Each lesson comes in three short parts: see the idea, try it on a live board, then build it yourself, with quick checks as you go.
“Ohm's law” is lesson 5 of 6 in Copper Flats, Electronics World 1. Free with an account. Lessons unlock in order, so you’ll do the 4 before it first.
Or start from the very first lesson, no account neededThe charts online
Work it out
The ideas behind it
- Ohm's law explainedV = I × R: set any two of voltage, current and resistance and the third follows.
- Electrical power explained: P = V × IP = V × I: how fast energy turns into heat, and why a resistor has a power rating.
- Voltage divider explainedTwo resistors that split a voltage: the formula, potentiometers, and why a load drags the output down.
- RC time constant explainedτ = R × C: how long a capacitor takes to charge through a resistor, and the 63% rule.
Questions teachers ask
Which formulas are on the sheet?
Ohm's law, power, series and parallel resistors and capacitors, Kirchhoff's laws, voltage and current dividers, the LED resistor, RC and RL time constants, reactance, impedance, filter cutoff, LC resonance, decibels, transistor and op-amp gain, and battery life.
Can students use it in an exam?
That's up to your exam board and your school. It holds formulas only, with a short note on what each one gives, so it works as an allowed formula sheet where one is permitted.
Is there a version with every formula?
The online electronics formulas cheat sheet lists every formula the lessons teach, more than a hundred, each linked to a guide. The printable keeps the ones a beginner uses most so it fits on one page.
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