Thermal Expansion
-is one thermodynamic phenomenon usually encountered. Most materials expand when their temperature increases. This is due to interatomic interactions within the molecule when the material is subjected to a temperature change.
Thermal Stress
-developed when tries to prevent the contraction and expansion of a material being subjected to temperature change.
Heat Capacity
-is the amount of heat required to raise its temperature by one degree. It is the product of the mass of the substance and its specific heat.
Thermodynamics
-the study of heat and its transformation into mechanical energy.
-stems from greek words meaning "movement of heat".
-it is the study of relationship involving heat, mechanical works, and other aspects of energy transfer.
-its foundation is the conservation of energy and the fact that heat flows from hot to cold. It provides the basic theory of heat engines.
Zeroth Law of Thermodynamics
-it states that if two objects are in thermal equilibrium with a third object, then they are in thermal equilibrium with each other.
-it is termed "zeroth" because it was historically stated after the first and second law of thermodynamics but has a more fundamental explanation than the two.
-this law follows the transitive property of equality from algebra(if a=b and a=c, then b=c).
First Law of Thermodynamics
-it states that the change of a system equals the difference between the heat taken in by the system and the work done by the system.
-the basis for this law is the principle on the conservation of energy which states that "Energy is created nor destroyed in any thermodynamic system.".
SIGNS FOR HEAT AND WORK IN THERMODYNAMICS
+Q - heat flow INTO the system with corresponding input of energy to it.
-Q - heat flow OUT of the system.
+W - work done BY the system against its surroundings which corresponds to E LEAVING the system.
-W - work done ON the system by its surroundings which corresponds to E ENTERING the system.
Adiabatic Process
-no heat transfer process.
-Q=0
Isothermal Process
-constant temperature process.
-change of U=0
Isochoric Process
-constant volume process.
-also known as isovolumetric process.
-W=0
Isobaric Process
-constant pressure process
-Q, change of U, & W = 0
Second Law of Thermodynamics
There are 3 versions of the second law of thermodynamics.
a)Kelvin-Planck Statement - no heat engine can completely convert heat energy to work. In other words, there is no 100% efficient heat engine.
b)Clausius Statement - heat flows naturally from hot to cold objects.
c)Entropy Statement - when a reversible process occurs, the total entropy of the universe remains the same. When an irreversible process occurs, the total entropy of the universe increases.
•Reversible process - the system and its surroundings can be returned to their initial state before the process occurs.
•Irreversible process - the system and its surroundings cannot be returned to their initial state before the process occurs.
Entropy
-greek word for transformation.
- it is used to represent the thermodynamic measure of disorder which was proposed by German engineer, Rudolf Clausius.
-it is represented by letter S.
-SI unit is J/Kg.
Entropy increases when heat is added to an object because •the molecules tend to move faster, •when gas flows from a container under high pressure to a space under low pressure, and •ice melts.
For reversible process, change in entropy of universe=0 while in irreversible process, change of entropy of universe>0.
Since entropy is a measure of disorder, an alternative entropy statement of the second law is "All natural or spontaneous process tend toward a state of greater disorder.".
The Origin of Electricity
Electricity began with man's curiosity on the peculiar ability of amber and lodestone to attract other materials.
Lodestone - known today as magnetized iron ore.
Amber - translucent yellowish-brown fossil resin.
As early as 600 BC, the Greeks were aware that amber could attract nearby objects when rubbed vigorously with a piece of cloth. The first recorded investigator of such ability of amber was Thales of Miletus, considered as one of the seven wise men of ancient Greece.
Much later in 1600, William Gilbert, physician to Queen Elizabeth I of England, found out that many other substances when rubbed against another substance have this ability of amber. He called these substances electrics which comes from the Greek word electron meaning amber.
The object is said to be electrified os said to have acquired charge when an object attracts smaller pieces of matter after being rubbed together. Since the charge is at rest, it is often referred to as Static Electricity.
Electrostatics - is the study of all phenomena associated with charged bodies at rest.
