Types of energy and reversibility of a process Describe the types of energy that change, the work done on the system, and the energy transferred through heating during the following processes. Indicate whether a reverse process can occur. (a) Water at the top of Niagara Falls cascades onto the blades of an electric generator near the bottom of the falls, rotating the blades and generating an electric current that causes a light- bulb to glow. The water, generator, lightbulb, and Earth are the
system. (b) Each second, your body converts 100 J of metabolic energy (converting complex molecules from food) to thermal energy transferred to the air surrounding your body.
The system is your body and the surrounding air. (c) The hot gas in a cylinder pushes a piston, which causes the blades of an electric generator to turn, which in turn causes a light bulb to glow briefly. The system is the original hot gas (which cools while pushing the piston), the generator, and the light bulb (which first glows and then stops glowing and cools down).