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tiffany schmuck Thermal Concepts
Thermal Concepts,tiffany kette
Try to define temperature. It's not so easy. It isn't heat. It isn't energy. What happens when you touch something with a lower temperature? Thermal energy flows out of you and into the colder object. The reverse happens when you touch something hot. Hot things make cold things warm. The heat flows from hot to cold, never the reserve. So it might be said that temperature determines which direction thermal energy flows. It can also be said that temperature is the measure of the average kinetic energy of molecules in a substance. Note: the terms average kinetic energy and mean kinetic energy are interchangeable.
What is thermal energy? Thermal energy represents the total internal energy of an object: the sum of its molecular kinetic and potential energies. Molecules have kinetic energy due to their motion,collana tiffany, both vibrational and translational. Molecules have potential energy due to the intermolecular forces. A simple model for a molecule would be masses connected with springs.
How about heat? Heat is defined as the transfer or change in thermal energy that is due only to a difference of temperature. Heat is not something a object has, but something that a object gets or gives up. Units for heat are Joules (J) or calories (cal). we'd like to put a number to it so we can predict which way the thermal energy will flow,nike free run, so we can know whether the house is going to get colder or get hotter. To put it simply we need a temperature scale. So how do we construct a temperature scale?
To construct a scale we need some way to measure the temperature. Often different physical properties of materials are used to measure temperature. Thermal expansion of a material is frequently used as a way of measuring temperature. As temperature changes the volume of materials changes as well,pull ralph lauren, if the change over a range of temperatures is linear then that material would make a good thermometer, or temperature measurer, over that range of temperatures.
We also need two reproducible temperatures,bracciale tiffany, these two temperature form anchors for the scale. The Celsius scale was based on the freezing point (0C) and the boiling point (100C) of water at standard temperature and pressure. This range of temperatures was then broken into 100 equal portions,tiffany schmuck, called degrees. The Fahrenheit scale was based on the freezing point of a salt water solution (0F) and human body temperature (98.6F). There are mixed reports as to how the number 98.6 was used. Some say it was originally 96, but there was experimental error, others say the temperature of a sick person (Fahrenheit's wife) was measured and thus the human body temperature was set at 100F It doesn't really matter, Fahrenheit sucks.
3.1,nike free.3 State the relationship between the Kelvin and Celsius scales of temperature,tiffany roma.
Celsius scale is nice in that it is based on two easily reproducible temperatures. However there are plenty of things colder than frozen water. Which creates negative temperature,tiffany hamburg, which is not a problem until put into an equation If the volume of a material (gas) varies with temperature,ralph lauren usa, say linearly as with the following equation:\beginequation V = kT \endequation
Then when the temperature is negative,new era, the equation gives a negative volume, which doesn't make any sense. This is a problem with the math not with the physics
It is convenient to have a scale with no negative values. Which is where the Kelvin scale comes in, zero degrees Kelvin is defined as absolute zero or when molecular motion is at a minimum. Absolute zero was first approximated using the volume and temperature relationship of gases. Different gases have different "k's" or constants but they are intersect at the same point (or roughly),tiffany girls, of course gases would liquefy or even solidify before reaching absolute zero. The intersection point is absolute zero. This was calculated to be 273C. This was later refined to be 273.16C. In recent years absolute zero has been measured to more decimals places,doudoune ralph lauren, but that doesn't really matter for this course A degree Kelvin is the same as a degree Celsius, but the zero is different.\beginequation T_K = T_C +273 \endequation
For the purpose of this class,timberlands, temperature in Celsius minus 273 is equal to temperature in Kelvin.
Note: When writing temperature in Kelvin no degree symbol is used,nike free run 3, 10 not 10K.
It is vital when using absolute temperature in equations to use Kelvin, however when using temperature differences it does not matter whether Kelvin or Celsius is used since a degree Kelvin is equal to a degree Celsius.
3.1.7 Describe qualitatively the processes of conduction,bracciali tiffany, convection and radiation.
3.1.8 Describe examples of conduction, convection and radiation.
Conduction is the process in which heat energy is transferred by adjacent molecular collisions throughout a material medium. The medium itself does not move. A simple example would be when you touch a cold piece of metal, thermal/heat energy flows out of your hand and into the metal,nike free 5.0 herren, there is no net motion of matter,nike free run 2, just heat flow.
Convection is the process by which heat is transferred by the actual mass motion of a fluid (gas or liquid). Most household heaters work this way,louboutin soldes. An object (a radiator) is heated the air around the object heats by conduction and then the air moves when it makes contact with a cooler object the heat energy is transferred,new era caps.
Radiation is the process by which heat is transferred by electromagnetic waves. The sun is the best example of heat transferred by electromagnetic waves. There is no material or medium between the earth and the sun for the heat to be transferred through,casquette ralph lauren, so it must be done by electromagnetic waves which require no medium to propagate.
hansen252 发表于：2014-3-12 15:45:13