Does the max amps of a wire change when the frequency increases?

Question

I am wondering, specifically about pulsed energies. Example say 10 joules at 12V were discharged extreemly fast, say 1mS, what would the minimum wire size be? I can find AWG specs fine, but no info with regards to pulsed or frequency apps.

Answer 1

The reason amps are specified for a wire are heating in the long term and voltage loss in the short term. Obviously the first does not apply here. The real problem is determining the actual amperage per second (flow) because you have both resistance and inductive factors. 10 joules in 1 ms in a perfect square wave would be 10,000 joules/second which is 10,000 watts, which at 12v is 833 amps which would require a heavy copper bar to carry it without significant loss. More likely, instead of a square wave, the shape would be more like a triangular wave or something curved, which would make calculations more complex.
With practical wiring that we are used to, it is unlikely that a discharge would occur in this size in this short a time because inductive losses would quench it before it peaked.

Answer 2

Technically yes. Because of the skin effect, high frequencies stay close to the surface of the wire; however in reality, for fast pulses (1 mS might as well be called DC) or high frquency applications, people use transmission lines and not just pieces of wire.