Thermal Conductivity Quiz

Heat Transfer Principles

• Heat transfer follows the principle: Heat Lost = Heat Gained, used in calculations involving water and aluminum.
• The final temperature (Tf) for a system was calculated to be 27.7 °C after reaching thermal equilibrium.

Heat Capacity Calculation

• Heat capacity of a copper calorimeter was calculated using the gained and lost heat equations.
• Gained heat by cold water: ( Q1 = 0.1 \times 4200 \times (38 - 10) = 11760 , J ).
• Lost heat by hot water: ( Q3 = 0.1 \times 4200 \times (38 - 80) = -17640 , J ).
• Heat capacity of the calorimeter calculated to be ( C = 210 , J/°C ).

Effects of Heat on Materials

• Increased temperature raises average kinetic energy in materials, leading to expansion.
• Heat expansion varies by state: gases expand more than liquids, which expand more than solids.

Types of Thermal Expansion

• Longitudinal expansion: increase in length (one-dimensional).
• Surface expansion: increase in surface area (two-dimensional).
• Volumetric expansion: increase in volume (three-dimensional).

Factors Influencing Thermal Expansion

• Length change is directly proportional to temperature change, original length, and material type.
• Surface expansion factor measures area increase per degree Celsius, denoted by specific units.

Heat Transfer Methods

• Heat transfer occurs via conduction, convection, and radiation.
• In solids, heat is mainly transferred by conduction; metals are good conductors due to free electrons.

Thermal Conductivity

• Thermal conductivity measures how well heat transfers through a material by conduction.
• The thermal gradient is defined as temperature change per meter length of a conductor.

Convection

• Free convection occurs due to density differences caused by temperature variations.
• Forced convection involves circulation of fluids using pumps or fans, enhancing heat transfer efficiency.

Radiation

• Heat radiation happens through electromagnetic waves. The wavelength depends on the temperature of emitting objects.
• Emitted radiation energy is affected by surface nature, area, color, and temperature of the object.

Factors Affecting Heat Absorption

• Materials vary in absorbed heat energy based on type, color, and surface smoothness.

Applications of Heat Transfer

• Specific applications include:
  • Plastic houses utilize radiation for thermal efficiency.
  • Solar heaters operate through radiation.
  • Central heating systems use both convection and radiation to distribute heat.

Thermal Pollution

• Thermal pollution arises from human actions leading to temperature increases in land, atmosphere, and water, disrupting environmental balance.