Re: "electron-to-joule conversion formulae"
Not to excuse the lack of correct science in a sci-fi TV show with warp drive and famously unreliable transporters, but phaser settings in electron volts wouldn't necessarily be calibrating the strength of the entire beam.
It could be a million electron volts per micron per attosecond or something, so depending on the specific area and time base used could easily be enough to destroy a city at full beam width.
Though on the evil Enterprise you'd think the bridge officers would know the correct settings to destroy a city by heart without Spock telling them, as they'd be doing that all the time. That would happen as often as "assume standard orbit, Mr. Sulu".
Biting the hand that feeds IT
