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What is Ohm's law?

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Quick answer

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.

Key things to understand

  1. The three quantities are voltage (V, the push), current (I, the flow), and resistance (R, the opposition).
  2. The formula V = I × R can be rearranged to find any one value from the other two.
  3. More voltage drives more current; more resistance reduces it.
  4. It applies to 'ohmic' materials, whose resistance stays roughly constant.
  5. It is the foundation for designing and analyzing almost every electrical circuit.

People also ask

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.

Part of the guide: Energy & Electricity at Home →