Electronics
Single-phase voltage drop
The factor of two accounts for the outbound and return conductors. Length is in kilometres when resistance is given in ohms per kilometre.
The Formula
V_drop = 2 L I R
The factor of two accounts for the outbound and return conductors. Length is in kilometres when resistance is given in ohms per kilometre.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| L | One-way length | kilometres | In kilometres, to match the resistance units. |
| I | Current | amperes | The load current in amperes. |
| R | Resistance per kilometre | ohms per kilometre | From the cable datasheet. |
| V | Voltage drop | volts | The volts lost over the whole loop. |
What Each Symbol Means
Lkilometres
One-way length
In kilometres, to match the resistance units.
Iamperes
Current
The load current in amperes.
Rohms per kilometre
Resistance per kilometre
From the cable datasheet.
Vvolts
Voltage drop
The volts lost over the whole loop.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate voltage drop 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 Voltage Drop, filed under Science. Every number the guide produces comes from substituting into this one line.