Flashcards: Conduction, Convection & Radiation

• Definition: Thermal energy in solids and liquids can be transferred by the vibration of particles, known as conduction.

• Conductors vs. Insulators:

Non-metals are usually poor conductors and are referred to as thermal insulators.
Metals are typically good conductors.

• Mechanism:

As a substance heats up, its molecules vibrate more vigorously.
These vibrations cause adjacent molecules to vibrate as well, thereby transferring heat energy from the hotter parts of the substance to the cooler parts.

• Role of Insulators:

Insulators transfer heat at a much slower rate, which is why they are used to minimize unwanted energy transfer, as seen in the construction of homes.

• Conductive Process in Metals:

In metals, the electrons are not fixed in place; they can leave their atoms and move freely among positively charged ions.
Upon heating, both ions and electrons vibrate more.
The free electrons collide with ions throughout the metal, facilitating the transfer of heat energy from hotter areas to cooler areas.

• Definition: Thermal energy in fluids (liquids and gases) can be transferred through a process called convection.

• Mechanism:

Convection occurs when molecules in a fluid, which are not rigidly held together like those in solids, move from areas of high thermal energy to areas of low thermal energy.

• Circulation Prevention:

Preventing circulation of the fluid can effectively reduce unwanted energy transfer through convection.

• Key Process in Fluids:

When a portion of a fluid is heated, it expands as the particles move further apart, resulting in lower density.
The less dense, warmer fluid rises to occupy less dense areas, while denser, cooler fluid descends to fill the space left behind.

• Examples of Convection:

• Definition: Thermal energy can be transferred through infrared radiation, which does not require a medium.

• Electromagnetic Spectrum: Infrared radiation is part of the electromagnetic spectrum.

• Black Body Radiation:

Black bodies with a dull texture are the best absorbers and emitters of radiation.
White bodies with a shiny texture serve as the best reflectors of radiation.

• Applications of Shiny Surfaces:

Shiny surfaces can be employed to minimize unwanted energy transfer (e.g., the surface of a vacuum flask).

• Factors Affecting Radiation Emission:

The higher the temperature of a body, the more infrared radiation it emits.
A larger surface area will also result in greater emission of infrared radiation.