IPC[1] FTW

specifically IPC-2152 - Standard for Determining Current Carrying Capacity in Printed Board Design

Ampacity and fusing currents

Breadboard wires are typically single-strand 24 AWG wire. Current flowing through these small wires causes them to heat up (like all resistances do); too much current and the wires melt — specifically, the insulation melts.

Use the data from Wikibooks: Engineering Tables/American Wire Gauge to compute the following quantities:

  1. Resistivity of copper in Ω·m

  2. Conductivity of copper in (Ω·m)-1

  3. Current density in A/m2 at the Preese fusing current of a 24 AWG wire

  4. Current density in A/m2 at the Preese fusing current of a 12 AWG wire

You might expect that because a 12 AWG wire is about 16× the cross-sectional area of a 24 AWG wire[2], then the fusing current would also increase by the same 16× factor — fusing at the same current density flux.

  • Why does the fusing current density change?



Think first, then click for an explanation

Sorry! The solution is hidden until/unless you have a science-backed description of your own first. Until then you may be interested that:

A similar volume to surface area effect was involved in the construction technique for the Hoover Dam. It would have taken about 125 years to cool off from the heat generated from the concrete curing process without active cooling. See The Story of Hoover Dam - Concrete.

1. Recently changed its name to Global Electronics Association
2. The area doubles for every 3 AWG decrease, approximately.