Electronics
Resistance from resistivity
The same relationship rearranged, which is how cable runs are sized.
The Formula
R = rho x L / A
The same relationship rearranged, which is how cable runs are sized.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| R | Resistance | ohms | The resistance of the length in question. |
| rho | Resistivity | ohm metres | The material property. |
| L | Length | metres | The length of the run. |
What Each Symbol Means
Rohms
Resistance
The resistance of the length in question.
rhoohm metres
Resistivity
The material property.
Lmetres
Length
The length of the run.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate resistivity page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Resistivity, filed under Science. Every number the guide produces comes from substituting into this one line.