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The expression for the infinitesimal reversible change in the Gibbs free energy as a function of its "natural variables" p and T, for an open system, subjected to the operation of external forces (for instance, electrical or magnetic) X i, which cause the external parameters of the system a i to change by an amount da i, can be derived as ...
The standard example of a longitudinal wave is a sound wave or "pressure wave" in gases, liquids, or solids, whose oscillations cause compression and expansion of the material through which the wave is propagating. Pressure waves are called "primary waves", or "P-waves" in geophysics. Water waves involve both longitudinal and transverse motions ...
The parameter defines the amplitude of the wave (that is, the maximum sound pressure in the bore, which is related to the loudness of the note); is the speed of sound; is the length of the bore; and is a positive integer (1,2,3,...) that specifies the number of nodes in the standing wave.
1.5 kW is the maximum legal power output of a US ham radio station. [12] 60 dBm: 1 kW = 1,000 W: Typical combined radiated RF power of microwave oven elements 55 dBm ~300 W: Typical single-channel RF output power of a K u band geostationary satellite: 50 dBm: 100 W: Typical total thermal radiation emitted by a human body, peak at 31.5 THz (9.5 μm)
A sound wave is a variation in air pressure, while in light and other electromagnetic radiation the strength of the electric and the magnetic field vary. Water waves are variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary. The range of wavelengths or frequencies for wave phenomena is called a spectrum.
Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time. For example, when a light bulb with a power rating of 100 W is turned on for one hour, the energy used is 100 watt hours (W·h), 0.1 kilowatt hour, or 360 kJ .
In addition, particle physicists design and develop the high-energy accelerators, [68] detectors, [69] and computer programs [70] necessary for this research. The field is also called "high-energy physics" because many elementary particles do not occur naturally but are created only during high-energy collisions of other particles. [71]
Renewable energy (also called green energy) is energy from renewable natural resources that are replenished on a human timescale. The most widely used renewable energy types are solar energy, wind power, and hydropower. Bioenergy and geothermal power are also significant in some countries.