Perpetual Motion Machines

• Concept: Machines that can output more energy than they consume, often depicted as ‘free energy’ devices.
• Violation of Thermodynamics:
• Perpetual motion machines violate the first law of thermodynamics, which states that energy cannot be created or destroyed, only transformed.
• Second law of thermodynamics further reinforces this notion by indicating that energy conversion is inherently inefficient.
• Patent Issues: There are numerous patent submissions claiming to create these devices, but they inevitably get rejected for violating established laws of physics.

Thermal Expansion

• Definition: The process whereby materials change their dimensions in response to temperature changes.
• Behavior:
• Expansion: Materials typically expand when heated.
• Contraction: Materials contract when cooled.
• Heat Energy and Heat Capacity:
• Heat must be added or removed to induce this change, which is connected to a material's heat capacity.
• Different materials require varying amounts of heat to change their temperature (e.g., water has a high heat capacity).

Thermal Conductivity

• Concept: The measure of how quickly heat can pass through a material.
• Example: In cooking, the heat from the pan is conducted upwards to the food (e.g., frying an egg).

Applications of Thermal Expansion

• Structures can suffer damage if thermal expansion is not accounted for.
• Expansion Joints: Installed in buildings and bridges to allow materials to expand and contract without causing structural damage.
• Real-Life Example: Cracks in roadways and buckling of concrete can occur due to improper design for temperature changes.

Calculating Linear Expansion

• Equation:
  ext{Change in length} ( riangle l ) = ext{Coefficient of linear expansion} (eta) imes ext{Original length} (l) imes ext{Temperature change} ( riangle T )
• Important factors:
• Original length
• Temperature change
• Coefficient of linear expansion (α): Represents how much a specific material expands per degree Celsius or Kelvin.

Temperature Scales

• Kelvin vs Celsius:
• Temperature changes are the same between the two (1°C change = 1 K change).
• Absolute temperature in Kelvin can often simplify thermal calculations.

Thermal Expansion Example

• Given values and variables:
• Mass of a given material, its original length, and specific temperature changes used to compute total change in length.
• Resulting calculations must express units correctly to avoid mistakes.

Specific Heat and Calorimetry

• Definition: The amount of heat required to change the temperature of a substance.
• Important Measurements:
• Water has a high specific heat (1 kcal/kg°C = 4184 J/kg°C).
• The specific heat (B,c]) varies by material and is determined through empirical testing.

Heat Transfer Calculations

• Formula:
  q = mc riangle T
• Application: Amount of heat changes with mass and specific heat when a material undergoes a temperature change.
• Examples highlight how to set equations for hot and cold thermodynamic systems.
• Equilibrium of Hot and Cold Systems:
• Energy lost by hot body = Energy gained by cold body.
• Resolving equations provides temperature after equilibrium is reached, often yielding final temperature results based on initial conditions.

Practical Applications

• Real-world phenomena such as bridges, roads, and buildings are designed concerning thermal expansion to prevent structural failures.
• Applications in everyday items, like dental fillings, also consider thermal expansion to ensure compatibility with surrounding materials.