Resistors & Ohm's Law in Practice
Pick a resistor so parts don't burn out.
Resistors & Ohm's Law in Practice is a free Arduino & IoT Academy lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Arduino & IoT Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
What a Resistor Does
A resistor limits how much current flows through a wire. It is the part that stops sensitive components from drawing too much and burning out. 🔥
Measured in Ohms
Resistance is measured in ohms, shown by the symbol Greek omega. More ohms means more push-back, so less current gets through.
Ohm's Law in One Line
Ohm's Law ties it together: voltage equals current times resistance. Know any two values and you can find the third.
V = I * RSolve for Current
Rearrange to find current: I equals V divided by R. Bigger resistance gives smaller current for the same voltage.
I = V / RWhy an LED Needs One
An LED has almost no resistance of its own. Without a resistor it gulps too much current and dies in a flash.
The Voltage Across It
Your pin gives 5V and an LED uses about 2V. The resistor must drop the leftover 3V, and that number sets its size.
Pick a Safe Current
A typical LED is happy near 10 to 20 milliamps. Aiming for about 15mA keeps it bright without stressing the pin.
Crunch the Numbers
Plug it in: 3V divided by 0.015A is 200 ohms. A common 220 ohm resistor is the easy, safe choice.
R = 3V / 0.015A = 200 ohmReading Color Bands
Resistors show their value with color bands. A 220 ohm part reads red, red, brown, a pattern worth memorizing.
Resistors Have No Direction
Good news: a resistor is not polarized. You can plug it in either way and it works exactly the same.
When in Doubt, Go Bigger
Unsure of the exact value? A slightly larger resistor just dims the LED a touch. That is far safer than too small. 👍
Quick Check
Apply Ohm's Law to a real choice.
Recap
You can now size a resistor with Ohm's Law: divide the leftover voltage by your target current, then round up to a safe standard value. 🎉
Frequently asked questions
Is the “Resistors & Ohm's Law in Practice” lesson free?
Yes — the full text of “Resistors & Ohm's Law in Practice” is free to read here on the web, and the Arduino & IoT Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Arduino & IoT Academy course, upgrade to CoddyKit PRO.
What will I learn in “Resistors & Ohm's Law in Practice”?
Pick a resistor so parts don't burn out. You practise Arduino & IoT Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Arduino & IoT Academy?
No prior experience is required. Arduino & IoT Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Resistors & Ohm's Law in Practice” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Arduino & IoT Academy lesson?
Yes. Every Arduino & IoT Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- How a Breadboard Connects
- Resistors & Ohm's Law in Practice
- Power, Ground & Common Mistakes
- Read a Simple Schematic