Sunday, March 1, 2009
Thermal physics is a field of science that deals with heat and temperature. When we study topics like global warming, the Earth's solid and liquid cores, and the way in which energy flows from the center of the Sun to its surface, we need to understand thermal physics.
Temperature is a familiar idea that is a big part of thermal physics. Three scales for measuring temperature are in common use: Fahrenheit, Celsius (or Centigrade), and Kelvin. The temperature of a gas is really a measure of the average speed with which molecules or atoms are hurtling about. We infer the temperatures of stars from their colors; hot stars are blue while cooler ones are red.
In our everyday speech, heat and temperature mean the same thing. In the language of thermal physics, the two terms have different meanings. Heat is the amount of thermal energy stored in an object. Heat can flow from one object to another, transferring energy in the process. The flow of heat can melt ice or warm the surfaces of planets near a star. The Laws of Thermodynamics describe the fundamental physics of heat and its flows.
Heat flows from hot places to cold ones, and often drives the motions of other materials. Convection and conduction are two common ways by which heat can flow. Electromagnetic radiation, especially at infrared wavelengths, can convey heat across a vacuum. We study heat flows to understand the circulation of ocean currents, the outflow of energy from the Sun, and the workings of rocket motors.
There are two types of thermodynamic instruments, the meter and the reservoir. A thermodynamic meter is any device which measures any parameter of a thermodynamic system. In some cases, the thermodynamic parameter is actually defined in terms of an idealized measuring instrument. For example, the zeroth law states that if two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. This principle, as noted by James Maxwell in 1872, asserts that it is possible to measure temperature. An idealized thermometer is a sample of an ideal gas at constant pressure. From the ideal gas law PV=nRT, the volume of such a sample can be used as an indicator of temperature; in this manner it defines temperature. Although pressure is defined mechanically, a pressure-measuring device, called a barometer may also be constructed from a sample of an ideal gas held at a constant temperature. A calorimeter is a device which is used to measure and define the internal energy of a system.
Reference taken from : http://www.windows.ucar.edu/tour/link=/physical_science/physics/thermal/sw_thermal.html and http://en.wikipedia.org/wiki/Thermal_physics
Reference taken from : http://www.windows.ucar.edu/tour/link=/physical_science/physics/thermal/sw_thermal.html and http://en.wikipedia.org/wiki/Thermal_physics
what we could have been, 9:48 PM.
