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I came into a debate with a friend about the nature of magical electricity, such as magical traps, shocking grasp, lightning bolt, etc. Is all arcane electricity Alternating Current (AC) or Direct Current (DC)? Can both be produced?

My leaning is towards it being DC based on the kinds of spells that are lightning/electrical damage. The reason I 'm asking was initially because of a debate regarding a ruling on whether or not wood conducts magical electricity.

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    \$\begingroup\$ This is an XY Problem. Instead of asking about what you think the solution is (modern scientific understandings of physics) you should describe the specific situation you had trouble ruling on and ask about how the rules of the game treat that scenario. \$\endgroup\$ – Thomas Markov Feb 17 at 2:29
  • \$\begingroup\$ Thanks, I've added clarification but it looks like it is still closed. \$\endgroup\$ – James Feb 17 at 2:31
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    \$\begingroup\$ @StopBeingEvil That answers the question, so it seems we are at least equipped to give an RPG answer to this question. \$\endgroup\$ – Thomas Markov Feb 17 at 2:45
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    \$\begingroup\$ I have already voted to re-open, because I feel I could answer this question as is, but I think the question could be improved if you expanded upon your reasoning about AC vs. DC with respect to the resistivity/conductivity of wood—because I’ve got an electrical engineering degree, and I can’t recall that ever being mentioned, nor do any cursory web searches reveal any significant change in wood’s conductivity between AC and DC electricity (I saw one mention of resistivity being dropping somewhat as you get to very high frequencies, but that was it). \$\endgroup\$ – KRyan Feb 17 at 3:17
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    \$\begingroup\$ Even aside from the "D&D is not a physics simulator", this question is badly posed. Google "Is lightning AC or DC?" for many explanations of why that, alone, is a badly posed question. \$\endgroup\$ – Novak Feb 17 at 4:01
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We have no means by which we could tell.

The overwhelming majority of electricity in D&D is described in terms of what it does to a creature. The effects of electricity on a living creature don’t vary all that dramatically based on it being direct or alternating—DC will tend to stop a heart, while AC will tend to cause fibrillation, but both conditions are quickly fatal. A stopped heart is somewhat more likely to restart than a fibrillating heart (hence the defibrillator, which is basically a big DC shock to stop the heart so it can hopefully restart), but so far as I know, D&D doesn’t have any rules about defibrillation. DC also tends to freeze muscles, while AC often causes spasms, but neither is really described by any of the electrical attacks we see in the game.

Electricity also usually causes burns, which is probably the most straight-forward thing to turn into (non-fatal) “lightning damage.” But AC and DC are both going to do that about the same.

Note there’s a lot on the net about which one is more dangerous, and a lot of it is urban legend. There’s some validity to some of it—AC voltages are reported by the “root mean square” voltage, which is less than the “peak” voltage, so when your wall outlet is said to be 120 V (US) or 240 V (EU) or whatever, the peak voltage is actually higher than that, whereas DC is (by definition) always the same value. If one has a situation where x V is dangerous, an alternating current with RMS voltage lower than x may still have moments where it exceeds x. And AC can induce a current through your body in circumstances where DC could not—DC always needs a complete loop.

But none of that applies to D&D, where we don’t have measured voltages or voltage limits, and we don’t really have to care about stuff like DC needing a complete loop because magic is forcing the electricity to move in ways it wouldn’t naturally. This is the really key thing—everything we know about AC vs. DC is suspect, because magical electricity unambiguously moves in ways that don’t match how natural electricity moves. If it did, it wouldn’t go where the spellcaster wants it to go—it would just follow the path of least resistance, as electricity generally does. In most cases, that’s going to be up the caster’s arms, through his body (likely causing cardiac arrest—either by stopping or fibrillating the heart), and into the ground. That isn’t what the rules describe, and lightning magic wouldn’t be very useful if it was.

Finally, on the subject of wood, its conductivity/resistivity¹ isn’t significantly affected by whether we’re discussing alternating or direct current. I have found some mention of especially high AC frequencies causing the resistivity of wood to drop, but this isn’t the primary concern in most of the literature. Rather, the big thing about wood’s conductivity, mentioned everywhere I could find that discussed the subject, was moisture content. “Oven dry” wood is a rather good insulator—it has high resistivity/low conductivity. But damp wood can conduct electricity quite fairly well.

Again, though, none of that matters much to magical electricity, though—because magic is forcing the electricity to go to places it wouldn’t otherwise. If magic is forcing it through the wood, it’s going to go through the wood even if some other path of lesser resistance is available. The only real question, basically, is how much power it’s going to take—and consequently, how hot the wood is going to get. Which, in D&D terms, is presumably related to how much lightning damage is being dealt. But since that’s abstracted to a fixed value, it would seem that perhaps magical electricity doesn’t even maintain that relationship.

  1. Resistivity (ρ) and conductivity (σ) are inverses of one another, ρ = ¹⁄σ and σ = ¹⁄ρ, so really we’re talking about the same physical attribute, just different ways of looking at it.
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D&D is not a physics simulator.

This search of the site shows numerous answers which echo this truism. D&D does not simulate real world physics. So it is going to be entirely up to the DM to decide what kind of current magical electricity is, if your DM even thinks it matters at all.

If one of my players asked me this question at the table, I would say “No, it’s magic”.

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    \$\begingroup\$ It's MC; Magic Current \$\endgroup\$ – MivaScott Feb 17 at 4:42
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    \$\begingroup\$ the fact it does not obey the normal rules of electricity support this. I can project it hundreds of feet at distant enemies while a steel clad fighter is standing right next to me points to the problem of trying tot apply real world physics to magic. \$\endgroup\$ – John Feb 17 at 6:16
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I believe there is a simple answer to this: It's neither, just like real-life lightning is neither as well. See this article where it explains that lightning is a composite of both, it's raw electromagnetic energy.

In the case of d&d I would also add that it doesn't even behave like normal lightning, as it doesn't follow the path of least resistance and it can ignore hundreds of people with kilos of metal on them in order to hit that single wizard in robes that was your target.

So in the end I would recommend that you either go with the "it's both" answer or you simply go with the third answer that others have already commented: "It's magic!, or simply it's Magical Current (MC)". Personally I like this last answer better, as it also explains the impossibilities that happen in lightning spells and effects in d&d.

Oh and regarding conductivity of wood I would rule it works like normal lightning: It doesn't exactly burn wood objects, it heats them so much that they may start burning at that specific point. After that, since wood is fuel it may end up burning, or may just get black and charred. Source: Ligntning strikes hitting trees, sticks used to create bonfire, etc.

However, d&d doesn't have any rule about lightning causing fire so as a DM I would only make it burn in certain circumstances, or if several strikes hit the same spot.

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