I have 2 wires (18AWG & 28AWG) of the same length which I connect to a power supply to deliver power to my board.

My board will consume around 400mA maximum.

Which wire will have more IR drop and how to understand the IR drop while selecting wires?

  • \$\begingroup\$ Are the wires connected in parallel or in series? What kind of wire did you use for the ground or return connection from the board to the supply? \$\endgroup\$ – The Photon Mar 4 at 15:43

The smaller diameter wires will commonly have higher resistance, thus higher voltage drops across the wire.

See here for comparison of different gauge wires.

| improve this answer | |
  • \$\begingroup\$ And once you know the ohms per metre (or ohms per foot) of your wire, the resistance of a given length of wire is easy to find - but don't forget to allow for the return wire. Then the volt drop is given by V = I²R. \$\endgroup\$ – Simon B Mar 4 at 13:48
  • \$\begingroup\$ @SimonB V = I²R? \$\endgroup\$ – DKNguyen Mar 4 at 13:56
  • \$\begingroup\$ @DKNguyen Silly me. The volt drop is given by IR. The power lost is I²R. \$\endgroup\$ – Simon B Mar 4 at 14:41

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