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So in my world, there are different types of elemental magic.

Regarding lightning (electric) magic, it functions by the user converting any kind of energy (say, kinetic) into electrical energy or simply directing lightning. As a result, most combatant lightning type magic users carry something that is able to make the most of the energy they put in with as little loss as possible.

What kinds of weapons would they carry? Also, I'm not sure if the electric produced would be enough to, say, kill a human? Or a horse, since common monsters in that world are around that size? Would they be able to generate enough electrical energy to power things? If so, would non-combatant lightning types primarily work at power plants? How would society shape with this change in power production? How badly would I be breaking physics?

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  • $\begingroup$ To make it compliant with energy conservation law, let the mages carry water. The energy would be coming from nuclear fusion of hydrogen. If anything goes, you may want to fuse the oxygen too. $\endgroup$
    – Alexander
    Commented Oct 29, 2020 at 23:25
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    $\begingroup$ You actually need very little electricity to kill a human (or horse) - the trick is to cause cardiac arrest rather than trying to burn them to a crisp. Of course in practice this would look a lot more like a Death spell than a Lightning spell ;) $\endgroup$
    – Gene
    Commented Oct 30, 2020 at 20:26

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Quoting the calculation I made in this other answer, a lightning produces between $2 \cdot 10^{12}$ and $2 \cdot 10^{15}$ W.

Even assuming that you are throwing a lightning at way shorter distance than what a naturally occurring one would travel, we are still talking about a huge amount of energy.

There is no way for the amount of gunpowder transportable by single man to produce a comparable amount of power.

Maybe if they carried nuclear pellets or weapon grade fissile materials.

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  • $\begingroup$ For reference, ammo used to hunt game has a muzzle energy (i.e.: kinectic energy as it leaves the muzzle) in the range of 2 kJ. That is orders of magnitude less than a lightning bolt. $\endgroup$
    – The Square-Cube Law
    Commented Oct 29, 2020 at 17:18
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    $\begingroup$ Be careful with power vs energy. You are quoting here power (W) and not energy (Wh). The energy of a lightning is still impressive, but orders of magnitude less so. $\endgroup$
    – Alexander
    Commented Oct 29, 2020 at 23:21
  • $\begingroup$ Energy of average lightning is equal to about 500 kg of modern gunpowder $\endgroup$
    – ksbes
    Commented Oct 30, 2020 at 10:58
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A single bolt of lighting carries about 5 GJ of energy, which is roughly equivalent to 38 gallons of gasoline. To generate one lighting bolt, your magic users will need to carry around over 220 pounds of gasoline, which is one of the most energy-dense, conveniently transportable fuels available. A typical bullet carries on the order of about 1 kJ of kinetic energy, which is only about a millionth of the energy carried by a lightning bolt. You're not going to achieve lightning-scale energy by firing bullets.

Of course, a lightning bolt is more than enough to kill someone (although it doesn't always kill), so you could dial this back somewhat and likely still have a lethal bolt. But at even a tenth of energy requirement, you're still taking about a pretty decent amount of fuel, so you're not going to be able to carry enough ammo to be shooting lightning bolts around willy-nilly. You might be able to carry enough fuel to shoot of a couple of weak bolts, but that's it.

All that said, Mr. Einstein has taught us that mass is energy. If your hero can create nuclear reactions that actually destroy mass, he'll have an enormous source of energy available literally everywhere there is matter. A single kilogram of mass is equivalent to tens of thousands of GJ, which would be more than enough. But this energy is far more difficult to unlock than a simple chemical reaction, however.

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Alright, the answers above are talking about shooting real lightning, but let's scale things down a bit because if we're using real physics that's not really reasonable. Let's talk Tasers.

I gave up after 3 Google searches and settled on this answer for how many Watts a police taser uses:

"The TASER Advanced M26c and TASER X26c are the most powerful units, discharging 50,000 voltsat 26 watts."

According to this article, that's less than a quarter the average energy usage of a human being throughout the day, indicating that turning "on" the Magic Taser(TM) would likely not be much more tiring than a heavy jog.

A Magic Taser(TM) is probably going to be limited in range to whatever object is manifesting the electricity (i.e. the Wizard's skin), but you could easily channel it through a sword or a long pole of some sort (or even your own armor).

Now, I know what you're thinking. A guy in metal armor is going to be insulated and not going to feel the effects of a Magic Taser(TM) especially since the existence of the Magic Taser(TM) will encourage steel plate makers to design their armor i nsuch a way that there are nice smooth electrical connections to the ground. I don't have a clever solution to that. That's just a natural build up of the arms race that develops from magical armaments.

But wait, this whole thing implies that Wizards need to get into reach of their target doesn't it?

Actually, that I do have an idea for. Introducing the Arrow Taser (TM). A steel arrowhead can make an excellent half of a capacitor (with the ground being the other half). With enough control over the forces of nature, a skilled Wizard can force an arbitrarily large buildup of charge in the arrowhead that will be dispersed upon contact with the ground. Of course, it need not be an arrowhead.

Introducing the Ball Bearing Trebuchet Taser Mark 1(TM). Hundreds of small steel balls launched by Trebuchet and charged by a Wizard, channeling the energy directly out of a burning vat of oil. Each one delivers a potentially deadly static discharge that will rain down on the enemy forces.

Ok, but seriously

Let's talk about the greatest source of energy that no one ever thinks about when they talk about harnessing energy to fuel magic, thermal environmental energy. If the laws of thermodynamics no longer hold you down, why could you not just pull the heat energy out of an object around you to charge anything you want.

A single kilo of water at STP (standard temperature and pressure) contains around 4 kJ of untaped thermal energy if you could just suddenly cool it to absolute zero. If you needed to generate the 5GJ of energy required to create a bolt of lightning (as cited by Nuclear Hogie), you merely have to lower the temperature of 5 million cubic meters of air 1 degree Celcius or do the same thing with 5,000 cubic meters of soil.

I couldn't hazard a guess as to what kind of crazy weather phenomenons you'd create from repeated castings of this kind of spell, but it's something to consider.

Edit: Mass is energy, and any Wizard worth their salt can see that. E = mc2 implies that you could generate a bolt of lightning off by turning a single object with a mass of around 0.000005 g into pure energy.

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