Science
What is Ohm's law?
Ohm's law is the basic rule of electric circuits: the current flowing through a conductor is proportional to the voltage across it and inversely proportional to its resistance. In short, V = I × R — voltage equals current times resistance.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains ohm's law.
Key things to understand
- 1The three quantities are voltage (V, the push), current (I, the flow), and resistance (R, the opposition).
- 2The formula V = I × R can be rearranged to find any one value from the other two.
- 3More voltage drives more current; more resistance reduces it.
- 4It applies to 'ohmic' materials, whose resistance stays roughly constant.
- 5It is the foundation for designing and analyzing almost every electrical circuit.
Frequently asked questions
- What is the formula for Ohm's law?
- V = I × R: voltage equals current multiplied by resistance. Rearranged, I = V / R and R = V / I.
- What is resistance?
- Resistance is how strongly a material opposes the flow of electric current, measured in ohms. Higher resistance means less current for the same voltage.
- Does Ohm's law always hold?
- It holds for 'ohmic' components with steady resistance. Some devices, like diodes and bulbs, are non-ohmic and don't follow it neatly.