What is an ohm?

An Ohm is the SI unit for electrical resistance and is symbolised by the Greek letter Ω.

The Ohm is related to the current and voltage in a system: a current of 1 amp through 1 ohm of electrical resistance produces a voltage of 1 volt across it.

The formula for this is I=V/R where:

I = the current through the conductor

V = the voltage measured across the conductor

R = the resistance of the conductor

Materials with a low resistance make good conductors – examples include copper and aluminium - whereas materials with very high resistance which make good insulators, such as PVC (Polyvinyl Chloride) and PE (Polyethylene).

Conductors are typically measured in Ohms (Ω) whereas insulators are measured typically measured in Mega Ohms MΩ.

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