Transmission of Heat and Thermal Properties

Vocabulary practice cards covering the physical principles of heat transmission, thermal conductivity, black body radiation, and laws of cooling based on the university lecture notes.

Conduction

A process of heat transmission where there is no actual movement of particles of the medium.

Convection

A process of heat transmission where heat is transferred through the actual movement of the medium particles; it requires gravity.

Radiation

A mode of heat transmission that requires no medium and involves no movement of particles.

Unit of Coefficient of Thermal Conductivity

The standard unit for this property is $\text{watt } K^{-1} m^{-1}$.

Coefficient of Thermal Conductivity (K)

A property that depends solely on the nature of the material and remains unchanged by variations in dimensions or temperature differences.

Rate of Heat Flow through a Window

A value determined by the formula $\frac{Q}{t} = \frac{KA\triangle\theta}{L}$, which is directly proportional to the temperature difference between the two sides.

Ideal Cooking Pot Material

A material characterized by low specific heat (to heat up quickly) and high thermal conductivity (to transfer heat fast).

Equivalent Thermal Conductivity (Series)

For two identical rods joined in series, the equivalent conductivity is given by $(K_{eq})_{s} = \frac{2K_1 K_2}{K_1 + K_2}$.

Equivalent Thermal Conductivity (Parallel)

For two layers of different materials with same thickness and area joined in parallel, the equivalent conductivity is $(K_{eq})_{p} = \frac{K_1 + K_2}{2}$.

Perfectly Black Body (PBB)

An ideal body that absorbs all incident radiations; it appears black when cold and emits all radiations (appearing white) when hot.

Kirchhoff's Law

A law stating that a good absorber of radiation is also a good emitter of radiation.

Stefan's Law

States that the rate of energy emitted per unit area of a black body is directly proportional to the fourth power of its absolute temperature, expressed as E = \text{e}\text{A}\text{\sigma}T^4.

Wien's Displacement Law

States that the maximum wavelength ($\lambda_{max}$) of emission is inversely proportional to the absolute temperature ($T$), expressed as \lambda_{max} T = \text{constant}$ or \lambda_{max} ext{ ∝ } T^{-1}$$.

Newton's Law of Cooling

States that the rate of loss of heat ($\frac{dQ}{dt}$) from a body is proportional to the excess temperature of the body over its surroundings ($\theta - \theta_s$).

Time for Ice Formation in Lakes

The time ($t$) required for ice to grow from thickness $y_1$ to $y_2$ is proportional to the difference of their squares, expressed as $t \text{ ∝ } (y_2^2 - y_1^2)$.