Absolute Zero

Absolute Zero

Absolute Zero Amontons hypothesized a state devoid of heat in a paper published in 1703. Absolute Zero All systems in thermodynamic equilibrium at absolute zero have vanishing entropy. This principle is called the Nernst heat theorem, or. the third law of thermodynamics. Walther Nernst(1864–1941) Germany. It is impossible reduce the temperature of any systems to absolute zero in a finite number of ...

Read More »

Energy & Entropy

Energy & Entropy

Energy & Entropy introduction Thermal pollution from a nuclear power Energy & Entropy plant near Perry, Ohio Waste energy is associated with all processes. This waste can be reduced, but it can never be eliminated. Anyone who says otherwise is trying to con you. The Second Law of Thermodynamics is a statement of the painfully obvious; that is, at least it’s obvious ...

Read More »

Refrigerators

Refrigerators

Refrigerators introduction Refrigerators is any kind of enclosure (like a box, cabinet, or room) whose interior temperature is kept substantially lower than the surrounding environment. The term “refrigerator” was coined by a Maryland engineer, Thomas Moore, in 1800. Moore’s device would now be called an “ice box” — a cedar tub, insulated with rabbit fur, filled with ice, surrounding a ...

Read More »

types of engine

types of engine

types of engine introduction types of engine The word “engine” is a bit old fashioned. At one time, an engine was any kind of mechanical contrivance. For example… The original, artificial computer was a mechanical device called the difference engine. I had to add the word artificial in there since the word computer originally referred to people whose job it was to perform ...

Read More »

Pressure-Volume Diagrams

Pressure-Volume Diagrams

Pressure-Volume Diagrams math, math, math Pressure-Volume Diagrams Recall from the previous section… ΔU = Q + W Q > 0 system absorbs heat from the environment Q < 0 system releases heat to the environment W > 0 work done on the system by the environment W < 0 work done by the system on the environment A system can be described by three thermodynamic variables — pressure, volume, and temperature. Well, ...

Read More »

Interfaces & Barriers

Interfaces & Barriers interface Interfaces & Barriers reflection Interfaces & Barriers transmission Interfaces & Barriers absorption absorption Sound, for example… The characteristic acoustic impedance (specific acoustic impedance?)… Z = ρv is important when calculating the amount of reflection and transmission at an interface. For the reflected portion, notice that when Z2 < Z1, the sign of the reflected portion is negative, which indicates a change of ...

Read More »

Heat & Work

Heat & Work

Heat & Work historical development ~1798 Benjamin Thompson, Count Rumford (1753–1814) no mass change after heat transfer work done boring cannons could boil water (frictional heating) cannons firing blanks get hotter than cannons firing cannonballs “Heat is a form of motion.” One of the few perfect sentences in the English language. (In what language was the orignal?) Taking a cannon (a brass six-pounder) ...

Read More »

Radiation

Radiation

Radiation introduction Radiation Heat radiation (as opposed to particle radiation) is the transfer of internal energy in the form of electromagnetic waves. For most bodies on the Earth, this radiation lies in the infrared region of the electromagnetic spectrum. One of the first to recognize that heat radiation is related to light was the English astronomer William Herschel, who noticed ...

Read More »

Convection

Convection

Convection Discussion the basics Convection is the transfer of internal energy into or out of an object by the physical movement of a surrounding fluid that transfers the internal energy along with its mass. Although the heat is initially transferred between the object and the fluid by conduction, the bulk transfer of energy comes from the motion of the fluid. Convection ...

Read More »