Ohm's Law: The Foundation of Every Circuit

If electronics were a cooking recipe, Ohm's Law would be the main ingredient. Without it, we cannot safely design any device, not even a simple blinking LED with an Arduino.

The Three Pillars of Electricity

Ohm's Law tells us how three basic physical parameters are interconnected:

• Voltage (V): Measured in Volts [V]. Imagine it as water pressure in a pipe.
• Current (I): Measured in Amperes [A]. This is the speed at which electrons move through the circuit.
• Resistance (R): Measured in Ohms [Ω]. This is the obstacle that resists the flow of current.

How to Calculate?

The easiest way to remember the formula is with the help of the triangle in the image above:

• If you are looking for Voltage: $V = I \cdot R$
• If you are looking for Current: $I = V / R$
• If you are looking for Resistance: $R = V / I$

Interactive Calculator

You don't have to struggle with manual calculations. Enter exactly two values into the fields below, and the tool will calculate the third one automatically. Important: Enter only numbers into the fields (no V, A, or Ω symbols). Use a period for decimal numbers (e.g., 0.02).

• Voltage: Enter only the value in Volts (e.g., 5 or 12).
• Current: Enter the value in Amperes. If you have milliamperes, convert them (e.g., enter 20 mA as 0.02).
• Resistance: Enter only Ohms (e.g., 220 or 1000 for 1 kΩ).