What this calculator does
Force Between Parallel Wires works out magnetic force per unit length between two long, straight, parallel current-carrying wires. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Current in wire 1 (A) | A number, measured in A. Starts at 10. |
| Current in wire 2 (A) | A number, measured in A. Starts at 10. |
| Distance between wires (m) | A number, measured in m. Starts at 0.05. |
| Wire length (m) | A number, measured in m. Starts at 1. |
| Current directions | Choose from Same direction, Opposite direction. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with current in wire 1
Every other input is held at the calculator’s starting values while current in wire 1 varies. Select any row to load that scenario into the calculator.
| Current in wire 1 (A) | Force per unit length | Force per unit length | Total force over given wire length |
|---|---|---|---|
| 5 | 2.0000e-4 N/m | 0.200000 mN/m | 2.0000e-4 N |
| 7.5 | 3.0000e-4 N/m | 0.300000 mN/m | 3.0000e-4 N |
| 10 | 4.0000e-4 N/m | 0.400000 mN/m | 4.0000e-4 N |
| 15 | 6.0000e-4 N/m | 0.600000 mN/m | 6.0000e-4 N |
| 20 | 8.0000e-4 N/m | 0.800000 mN/m | 8.0000e-4 N |
| 30 | 1.2000e-3 N/m | 1.2000 mN/m | 1.2000e-3 N |