When electric current flows through the conductor, it experiences some resistance, because charged particles (the current) are hitting the particles of the conductor's molecular structure. The electrical resistance R is the measure of the objects opposition to the flow of electric current.
The active resistance of the electrical circuit conductor element is calculated as:
- ρ - electrical resistivity [Ω*m]
- l - conductor's length [m]
- A - conductor's cross section area [m2]
Electrical resistivity (also called specific electrical resistance) is material specific. For metals it is increasing with higher temperature. The typical values at 20°C are:
|Wood||103 to 104|
Also, resistance is proportional to the conductor's length, and inversely proportional to the cross section area, because the thinner the wire is, the harder is for the electric current to walk through.