Resistance and Ohm’s Law

Why do we get resistance?

An electric current flows when charged particles called electrons move through a conductor. The moving electrons can collide with the atoms of the conductor. This makes it more difficult for the current to flow, and causes resistance. Electrons collide with atoms more often in a long wire than they do in a short wire. A thin wire has fewer electrons to carry the current than a thick wire. This means that the resistance in a wire increases as:

  • the length of the wire increases
  • the thickness of the wire decreases

Ohm’s Law

Resistance is measured in ohms. The symbol for an ohm looks like this: Ω The greater the number of ohms, the greater the resistance. The equation below shows the relationship between voltage, current and resistance: potential difference (volt, V) = current (ampere, A) × resistance (ohm, Ω )

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