PHYSICS WA#1

• Heat Transfer occurs due to CONDUCTION, CONVECTION, and RADIATION
• CONDUCTION:

  • Temperature Difference
  • Direct Physical Contact
  • Collision of Particles
• CONVECTION:

  • Fluid (Liquid or Gas)
  • Temperature Difference
  • Air Circulation
• RADIATION:

  • No Medium Requires
  • Temperature Difference
  • Emission of EM Waves
• HEAT TRANSFER:

  • Involves movement of thermal energy from one system to another due to temperature difference
• Temperature: - Measure of average kinetic energy of particles.

  • Result of gain or loss of heat.
  • Point function
• Heat: -Transfer of energy between two bodies due to temperature difference.

  • Path Function
  • Flows from hot to cold area
• Thermal Energy: -Total amount of internal energy possessed by the particles of matter.

  • Stored in the system as kinetic energy of particles
• QUANTIFICATION:

  • Measuring temperature, heat, and thermal energy is crucial for accurate scientific understanding, efficient engineering design, and practical applications across multiple fields.
• Temperature:

  Degrees Farenheit

  Degrees Celsius

  Kelvin

  Rankine
• Heat

  Joules

  Calories
• Thermal Energy:

  Joules
• Phase Changes:

  -absorption or release of heat

  • Enthalpy is denoted by “h” and refers to the measure of total heat content in a thermodynamic system under constant pressure (at which the system is maintained).
  • H=U+PV
• • Energy is conserved in chemical reactions. The amount of energy in the universe at the end of a chemical reaction is the same as before the reaction takes place.
• Exothermic Reactions:

  chemical reaction that release heat and has a negative standard enthalpy change

  Ex: Campfire, water and acid reaction, rusting, Nuclear fission, Freezing water to ice
• Endothermic Reaction: absorb heat from their surroundings and feel cold

  Ex: Photosynthesis & Dissolving water and salt
• • THERMODYNAMICS
  • Branch of physics that studies the relationships and interactions between heat, work, temperature, and energy in macroscopic systems. It provides a framework for understanding and predicting the behavior of substances and systems undergoing changes in state, whether it be the expansion of gases, phase transitions, or the operation of heat engines.
• Energy Transfer:

  Heat:

  Energy flows

  Work(Classical Mechanics):

  Energy converts

  Work (Thermodynamics):

  Energy flow
• Cause of Heat Flow or Transfer:

  Heat:

  temperature difference

  Work (Classical Mechanics):

  Applied Force

  Work(Thermodynamics):

  Temperature difference
• Common Symbol:

  Heat:

  +Q (Heat added to the system)

  -Q (Heat removed to the system)

  Work (Classical Mechanics):

  +W (Work done upward or same direction of force application)

  -W (Work done downward or opposite direction of force application)

  Work (Thermodynamics):

  +W (Work done on a System)

  -W (Work done by a System)
•  heat engine is a device that converts thermal energy (heat) into mechanical work. they are crucial components in various applications, including power generation, transportation, and industrial processes
• • ΔU = Q - W
  • ΔU

  change in internal energy of the system

  • Q

  heat added to the system

  • W

  Work is done by the system

  • If work is done...

  Internal energy of a system changes.
• • “Heat Can do Work”

  Energy transferred to a system in the form of heat can be used to perform work or contribute to changes in the system's internal energy.
• Several factors influencing the amount of work done

  • The work done (W) is directly proportional to the pressure change (P) in many processes, especially those involving compression or expansion.
  • The work done is directly proportional to the change in volume (ΔV), particularly in processes where expansion or compression occurs.
  • The type of process can impact the work done. For example, isobaric processes (constant pressure) involve direct relationships, while isochoric processes (constant volume) have no work done.

  
• Several factors influencing the amount of work done:

  • In isothermal processes (constant temperature), the work done is directly proportional to temperature. In adiabatic processes (no heat exchange), the relationship is complex.
  • The nature of the system affects the work done, with different materials or substances exhibiting different behaviors under changing conditions.
  • Mechanical efficiency considerations, which account for losses, can lead to lower actual work output compared to the theoretical maximum.

  
• ΔU = Q - W:

  The change in internal energy of the system is equal to the heat input minus the work done by the system. If the internal energy of the system increases, more heat is added than the work done, and if the internal energy decreases, more work is done than heat added
• Efficiency = W / Q:

  • The efficiency of a heat engine, for example, is often expressed in terms of the ratio of work output to heat input.
• Laws of thermodynamics:

  • zero
  • first
  • second
  • third
• the zeroth law of thermodynamics

  • Equilibrium principle
  • two bodies in thermal equilibrium are at the same temperature
• The first law of thermodynamics:

  • Energy principle
  • Energy cannot be created nor destroyed
• The second law of thermodynamics:

  • entropy princple
  • an isolated system increases in any irreversible process and is unaltered in any reversible process
• The third law of thermodyanics

  • temperature principle
  • it is impossible to reach a temperature of absolute zero
• Laws of thermodynamics and their issues

  Zeroth:

  • Different thermometric systems and temperature scales may be subjective to human experiences and not universally applicable.
  • Quantum effects and fluctuations in microsystems might lead to deviations from classical thermodynamics
• Laws of thermodynamics and their issues

  First:

  • assumes closed systems, and applying it to open systems may require additional considerations.
  • Some processes are irreversible, and the  does not specify the directionality of processes.
• Laws of thermodyanics and their issues:

  Second:

  • Evolution appears to involve an increase in complexity and organization.
  • Raises questions about the ultimate destiny of complex structures and information in the universe.
• Laws of thermodyanics and their issues:

  Third:

  • Existence of a perfect crystal.
  • Raises questions about the ultimate destiny of complex structures and information in the universe. Achieving temperatures very close to absolute zero.
• Heat pump:

  A heat engine that runs in the reverse direction. They transfer thermal energy by absorbing heat from a cold space and releasing it to a warmer one