Most energy efficent attacks in a physics-bound magic system

Question

I'm currently working on devising a magic system in which all the standard laws of physics are upheld (Conservation of mass/energy, thermodynamics/entropy, and more).

'Powering' the Spell:

To keep it brief, my magic system allows spellcasters to convert one state or type of energy to another and project that energy outside of their own bodies. A typical spellcaster would fuel their spell using the chemical energy from their bodies/muscles (ATP). "Forms of energy" or "Types of energy" include classical energy types like Mechanical, Electrical, Magnetic, Gravitational, Chemical, Nuclear, Radiant, Thermal, etc.

After a spellcaster has chosen an energy source, they can begin to "channel" the spell at a specific rate. Doing so expends energy (Joules, Kilocalories) and happens at a specific power, or rate of energy expenditure (Watts). How much power a spellcaster can channel from their physical bodies is shown in the graph here.

For example, if my spellcaster is super fit and is going "all out" they'd be able to channel ~2000 Watts for three seconds before they collapse from exhaustion.

'Casting' the Spell

Once the spellcaster has harvested some energy, they can convert this to any other type of energy. Where and how this energy manifests itself is up to the spellcaster however its power decreases roughly with the inverse square of the distance to the spellcaster. Additionally, the energy can't manifest itself directly inside mana-rich regions such as other creatures (this prevents pinch-the-brainstem style attacks).

The form this energy can take is diverse and primarily limited by the spellcaster's understanding of reality/physics. This means to cast a spell which draws upon Nuclear power or other more advanced power sources requires an intimate understanding of how it exactly works.

The question: How would combat look with this magic system?

More specifically, what method would spellcasters use to attack others (spellcasters and non-spellcasters alike) while expending as little energy and power as possible?

Examples of spells:

• Applying kinetic energy to small projectiles and building up their speed by orbiting them around the spellcaster until releasing them at a target
• Generating a "laser beam" or bright beam of intense light to blind or stun opponents
• Electric shocks on skin contact to stun attackers

Answer 1

Blow their eardrums out

The loudest noises people can handle "only translates to about a hundredth of a watt per square meter". So have your mage pick out the 3 square centimeters immediately adjacent to your enemy's ear and blast them with the loudest sound anyone has ever heard. Guaranteed they'll be disoriented and hopefully rendered unconscious.

Bonus Apparently it only takes 200 db to kill someone, and sounds at 165 db are loud enough to ignite your hair.

Answer 2

Set the air on fire

The specific heat capacity of air is 1.00 kJ/Kg. 1 Liter of air weighs approximately 1.225 g. Therefore it costs 1.225 Joules to raise 1 liter of air 1 degree Celsius. Assuming you have 6000 Joules to play with (2000 J/s * 3 seconds) you should be able to easily raise the temperature of the air directly in front of your opponent's face to super high levels either burning their respiratory passage, eyes, or face.

Answer 3

Administer a poison

It takes approximately 0.0000001g of Botulinum toxin to kill a human. Have your mage carry around a pouch of this, or something similarly toxic and float a tiny quantity of it into their opponent's face where they'll either inhale it or swallow it. This may not be the most fast acting poison though, so more suited to assassinations, but you could use a more immediately debilitating posion if you're engaged in combat.

Answer 4

Magic gun time!

I'm imagining something similar to a rifle, except that instead of a chemical detonation, the wizard produces a magical one. Seems simple and straightforward enough that it could be used quite broadly without years and years of training. As for fuel, as far as I understand, the wizard would just need to carry a pouch of pig fat or mashed potatoes and consume the chemical energy of that to fuel the magical detonation, instead of their own ATP.

Also allows your wizards to shout out "I cast bullet!" before blasting somebody's head off, which would be quite entertaining.

Answer 5

I think by description the most efficient way of combat is physical damage to specific vulnerable parts of human anatomy.

Such as, aiming for the neck and trying to damage either breathing tube or blood vessels or spine. Or aiming for eyes.

Can it bypass armor, such as, can mages apply this energy to places which are not geometrically reachable? If it can't, the cold iron will still rule. In this case, go for the horse (eyes or ears). Against a prepared melee fighter, this can be a problem.