In an oven what kind of energy is used?
That's kind of a trick question! Most ovens are either gas or electric. But they cook by heating the food. So, an oven uses either chemical energy in the form of gas, or electrical energy, but either one is converted to heat energy to do the actual cooking.
The electricity (electromagnetic energy) that drives the microwave oven is routed to the magnetron, which generates the microwave energy. (The electricity and microwave energy are both forms of electromagnetic energy.) The microwaves travel through a waveguide into the cavity (the cooking space) in the oven, and used to excite chemical bonds in the food items. This is a conversion of microwave energy (electromagnetic energy) into the mechanical energy of heat.