# Electrical resistance and conductance

opposition to the passage of an electric current

Resistance, measured in ohms (symbolized by the Greek letter omega - Ω), is a measure of the opposition to current flow in an electrical circuit.

When an electron moves through a conductor like a meatal wire, is when an electric current would flow. Colliding of different moving ions in the metal makes it harder for current to flow which is what causes resistance.

The longer a wire is, the more resistance there is because of the amount of collisions within being more as they pass; this means that the relationship between the two are proportional.

On the other hand, the thinner a wire is, the more resistance. This is because of the space of the passing ions being less meaning the collisions increase. That makes them inversely proportional.

As Resistance increases, current decreases making them inversely proportional.

## Calculation

Resistance can be calculated by measuring current via an ammeter and potential difference via a voltmeter and using Ohm’s law.

V = I x R

or

Volts = amperes x ohms

Or

Potential difference = current x resistance

Which can be re-arranged to calculate current:

R = V/I