Thermal Energy Transfer and Equilibrium - AP Physics 2

Perfectly absorbs all incident radiation. Ideal absorber with emissivity equal to 1.

Watts per meter per Kelvin (W/m·K). SI unit for thermal conductivity in the fundamental units.

Emissivity measures how effectively a surface emits thermal radiation. Ranges from 0 to 1, with 1 being a perfect emitter.

First Law of Thermodynamics. Conservation of energy principle in thermodynamic systems.

It transfers heat efficiently. Good conductors allow rapid heat flow between objects.

Heat. Heat is energy in transit, temperature measures thermal state.

The rate of heat loss of a body is proportional to the temperature difference with its surroundings. Describes exponential cooling behavior of heated objects.

Energy cannot be created or destroyed; it is transferred or changed in form. First Law of Thermodynamics applied to thermal systems.

$\triangle T = \frac{Q}{mc}$. Rearranged form of $Q = mc\triangle T$ solving for temperature change.

Conduction. Direct contact between particles enables heat transfer.

First Law of Thermodynamics. Conservation of energy principle in thermodynamic systems.

Radiation. Electromagnetic waves carry energy through vacuum or space.

The power radiated from a black body in terms of its temperature. Power is proportional to the fourth power of temperature.

Energy is absorbed or released without changing temperature. Latent heat causes phase transitions at constant temperature.

$Q = \frac{kA(T_2 - T_1)t}{d}$. Fourier's law where k is conductivity, A is area, d is thickness.

Heat flux is proportional to the negative gradient of temperature. Heat flow rate is proportional to temperature gradient.

Watts per meter per Kelvin (W/m·K). SI unit for thermal conductivity in the fundamental units.

A device that absorbs and dissipates heat from another object. Conducts heat away from components to prevent overheating.

Material type and temperature change. Coefficient of expansion varies by material and temperature range.

It is the state when two objects in thermal contact no longer exchange heat. Both objects reach the same temperature at equilibrium.

Minimizes conduction, convection, and radiation. Vacuum and reflective surfaces block heat transfer mechanisms.

Increase in volume of a substance due to heat. Materials expand when heated due to increased molecular motion.

Perfectly absorbs all incident radiation. Ideal absorber with emissivity equal to 1.

Surface area, temperature, and emissivity. All three factors determine the rate of radiant heat transfer.

Lower thermal conductivity means better insulation. Poor conductors prevent heat flow, making good insulators.

Correct: Heat flows from hot to cold spontaneously. Heat naturally flows from higher to lower temperature regions.

Joules per kilogram (J/kg). Energy per unit mass for phase change processes.

$Q = mc\triangle T$. Where Q is heat, m is mass, c is specific heat, and $\triangle T$ is temperature change.

Emissivity measures how effectively a surface emits thermal radiation. Ranges from 0 to 1, with 1 being a perfect emitter.