A lot of people are talking about the Thor attack of Luffy, so I will give my two cents.
The way I see it, is not like Luffy makes Electricity, but he gives the name because of electricity, created on the impact. The same happens in the Red Hawk, Luffy doesn't make fire, but the name is because of the explosive impact(In the anime it was shown flames in Luffy arm, before the impact, but that is different from what happened in the manga).
Let me explain. The logic in the Red Hawk making a Strong and Fast enough Impact that even creates flames, Literally an explosion, the flames are from the impact and not from the temperature of his arm. With Gear Second Luffy gets the speed and with the Armament Haki the strength needed to create the massive Explosion(That is the reason Ideo punches make explosions.)
The Logic of Thor is similar. A Strong Impact, but not fast enough to generate the energy to create an explosion, between two stiff enough objects, normally metal, create a lot of sparks, making the representation of such kind of impacts sparks. With The combination of Gear Third, Armament Haki and gravity force(from the fall) Luffy gets the Strength and stiffness needed to create an abnormal quantity of Sparks from a shock with an enemy, that for a fraction of a second keeps up with him.
He names these two attacks because of their end results, the kind of impact created(if everything goes as plan), and not because he manipulates Fire and Electricity.