Compare and contrast several different forms of energy.
Answers
Explanation:
Types of Energy
Mechanical Energy
Mechanical energy is the energy associated with motion. The amount of energy depends on the mass and velocity of the relevant system or component. Objects that have greater mass or motion at a higher speed have higher kinetic (or mechanical energy). It also includes the potential for motion, such as with gravitational potential energy (for example from elevated water) or elastic potential energy (for example from a coiled spring).
Thermal (Heat) Energy
Thermal energy (or heat) is a measure of kinetic energy at the molecular level. Heat and temperature are proxy measurements for the motion of molecules. What we feel as heat is really energy being transferred to our bodies from molecules colliding against us. Molecules move faster in hot weather, colliding against us with higher velocity, which feels warm. In many systems, thermal energy is held in working fluids such as steam, refrigerants, molten salts, or specialty oils. In power plants and heating districts, thermal energy is typically carried in steam. In cooling districts or refrigeration systems, thermal energy is carried in chilled water or refrigerants such as R-142a or ammonia.
Electrical Energy
Electrical energy (or electricity) is ubiquitously familiar to the developed world as a common form of secondary energy in the built environment. This form of energy is carried in currents and driven by voltages across loads (or resistances).
Radiant Energy
Radiant energy includes those forms of energy that travel in waves. Examples include electromagnetic radiation, such as light and magnetic forces. Thus, light waves carry energy, which is a simple explanation for how sunlight can cause burns. Acoustic waves also carry energy. Microphones detect this energy to make an audio recording. Conversely, very powerful weapons destroy buildings using intense acoustic waves.
Chemical (Fuels) Energy
Chemical energy is the energy stored in the chemical bonds of molecules. During combustion, fuels burn and the chemical bonds break, releasing heat. The energy content of fuels depends on the composition, masses, and other properties of the molecules. Chemical energy is responsible for more than 85% of the energy consumption around the world in the form of fossil fuels (coal, petroleum, and natural gas) and bioenergy (wood, alcohols, straw, and cow dung).
Atomic (Nuclear) Energy
Atomic energy is the energy stored in the nucleus of atoms. During reactions, atomic bonds break, releasing heat. Einstein’s famous equation relates mass and the energy contained within: E = mc^2. For this equation, E is energy, m is the mass lost during a conversion, and c is the speed of light. In other words, because the speed of light is so large (light moves at a rate of 30 billion centimeters per second), small changes in mass yield tremendous energy. During atomic reactions, minuscule amounts of mass disappears, but because of the relationship, the reactions release significant energy.
Energy Conversions
Energy can be converted between different these different types. The First Law of Thermodynamics tells us that energy is conserved when it transforms. That is, you never have more energy after a transformation than you started with.
If you follow the path of energy involved in turning on a light, you typically begin with the chemical energy of a fuel, usually coal or natural gas, which is burned in a boiler at the power plant to make thermal energy. That thermal energy is used to change water to pressurized steam. A turbine captures the heat and pressure of the steam and converts it into mechanical energy. The spinning turbine turns coils of wire past magnets in a generator, which converts the mechanical energy into electricity. The electricity comes down wires into your home, where the light bulb converts it into radiant energy, light. If you’re using an incandescent light bulb—the kind that Edison invented—you’re also converting the electricity into heat. A lot of heat, actually. About 95% of the energy that goes into an incandescent bulb comes out as heat.
While the First Law tells us that energy is always conserved, the Second Law of Thermodynamics goes even further. Every time you transform energy, some of it is lost in the process. The fuel isn’t burned completely, the turbine doesn’t capture all of the energy in the steam, the spinning shaft in the generator has friction, which makes heat, and so on. In fact, assuming you’re using an incandescent light bulb, only about 1.5% of the original energy in the fuel is converted into light. The other 98.5% is lost along the way, mostly as heat.