LESSON 03 · Foundations
Ohm's Law
One equation that connects voltage, current, and resistance.
Ohm's Law states that voltage equals current multiplied by resistance:
THE FORMULA
V = I × R (rearranged: I = V ÷ R, or R = V ÷ I)
This lets you find any one value if you know the other two. Say you have a 9V battery and a 1,000Ω resistor: the current through it is 9 ÷ 1000 = 0.009A, or 9 milliamps.
- Raise voltage, current rises too (resistance fixed).
- Raise resistance, current falls (voltage fixed).
- You'll use this formula constantly to pick the right resistor for an LED — covered in Lesson 10.