5.1 Thermal Physics

Absolute Temperature

A temperature value relative to absolute zero.

Absolute Zero

The lowest possible temperature of a system, where no heat remains and the particles in the system have no kinetic energy.

Avogadro Constant

The number of particles that make up one mole of any gas.

Boltzmann Constant

A constant relating the average kinetic energy of the particles in a gas to the gas’s temperature.

Boyle’s Law

The pressure of an ideal gas is inversely proportional to its volume when held at constant temperature.

Brownian Motion

The random motion of particles.

Change of Phase

The transitions between solids, liquids, and gases. During a change of phase, there is a change of internal energy but not temperature.

Equation of State of an Ideal Gas

An equation linking pressure, volume, number of moles, temperature, and the ideal gas constant.

Gas

A phase of matter in which the particles are high energy and free to move. Gases will fill the space they are placed in.

Internal Energy

The sum of the randomly distributed kinetic and potential energies of the particles in a given system.

Kelvin

The unit of absolute temperature.

Liquid

A phase of matter in which the particles can slide over each other but still have forces of attraction between them.

Solid

A phase of matter in which the particles can only vibrate about fixed positions, due to strong intermolecular forces.

Specific Heat Capacity

The amount of energy required to increase the temperature of 1 kg of a substance by 1 K.

Specific Latent Heat

The amount of energy required to change the state of 1 kg of a substance without a change of temperature.

Thermal Equilibrium

A stable state in which there is no thermal heat transfer between two regions.

Angular Velocity

An object’s rate of change of angular position.

Centripetal Acceleration

The acceleration of an object moving in circular motion; direction constantly changes, so acceleration is required.

Centripetal Force

The resultant force responsible for an object moving in circular motion; it always acts towards the centre.

Frequency

The inverse of the time period; the number of rotations per unit time.

Period

The time taken for one whole rotation.

Radian

A unit of angle, where 2π radians equals one complete rotation.

Angular Frequency

A measure of an object’s angular displacement per unit time.

Critical Damping

The form of damping that reduces displacement to equilibrium in the quickest time possible without further oscillation.

Damping

The dissipation of energy from an oscillating system, causing amplitude to decrease.

Forced Oscillations

Repeated oscillations at the frequency of a driver; amplitude is small at high frequencies and large at low frequencies.

Free Oscillations

Oscillations not caused by a driver; occur at the system’s natural frequency.

Isochronous Oscillator

An oscillator whose frequency is independent of amplitude.

Natural Frequency

The frequency a system naturally oscillates at when there is no driving force.

Overdamping

Damping greater than critical; system returns to equilibrium more slowly and without oscillating.

Resonance

Occurs when the driving frequency equals the natural frequency; energy transfer is at a maximum.

Simple Harmonic Motion

Motion where acceleration is directly proportional and opposite to displacement.

Underdamping

A type of damping where energy is gradually removed and amplitude slowly decreases.