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Say I've calculated the minimum wire gauge necessary to give me an acceptable voltage drop over my length of cable run at the voltage and current my application will use.

Are there any disadvantages to using thicker cable, aside from cost? Is the answer different for AC vs DC? For power vs signal transmission?

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Electrically, thicker is better in this case. However, thicker cable has other disadvantages beyond just the extra cost:

  • Less flexible. This makes it harder to install and harder to work with in general.

  • Bigger, which means it might not fit thru some small holes or tight places.

  • You get diminishing returns with AC due to the skin effect. Thicker is never worse than thinner electrically, but after some diameter the extra area gives you less and less return. This effect is proportional to frequency, so thicker cable is more useful for something like 60 Hz power as apposed to 10 kHz signal to a loudspeaker.

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    \$\begingroup\$ And when dealing with both power and fast signals, larger geometries generate higher inductivity which causes problems with inductive kicks and slew rate respectively. (by the way, when can I start giving people badges? because what you wrote here is exactly what I was about to write, really nice answer) \$\endgroup\$
    – user36129
    Aug 7 '13 at 15:38
  • \$\begingroup\$ @user26129 Badges are awarded by the system, not by users. You can upvote good comments and answers, which indirectly contribute to badges. \$\endgroup\$
    – JYelton
    Aug 7 '13 at 16:45
  • \$\begingroup\$ Heavier, which can matter in portable or implanted systems. \$\endgroup\$ Aug 7 '13 at 20:07
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    \$\begingroup\$ The tip about thicker cable for fast AC giving diminishing returns is the kind of non-obivious kind of thing I was looking for, also user2619's comment about induction and slew. Awesome answers, thank you all. \$\endgroup\$ Aug 8 '13 at 19:53

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