Kelvin

Definition

Kelvin is the base unit of temperature in the International System of Units (SI), named after the physicist William Thomson, Lord Kelvin. It is a fundamental unit that is used to measure the absolute temperature of a system, providing a scale that is independent of the properties of any particular substance.

5 Must Know Facts For Your Next Test

1. The Kelvin scale is the only temperature scale where the lowest possible temperature, absolute zero, is defined as 0 Kelvin.
2. Kelvin is the base unit for temperature in the International System of Units (SI), with the symbol K.
3. The Kelvin scale is an absolute temperature scale, meaning it does not use an arbitrary starting point like the Celsius or Fahrenheit scales.
4. A change of 1 Kelvin is equivalent to a change of 1 degree Celsius, but the Kelvin scale starts at absolute zero, which is -273.15 degrees Celsius.
5. The Carnot cycle, an idealized thermodynamic cycle, uses the Kelvin scale to determine the maximum theoretical efficiency of a heat engine.

Review Questions

• Explain how the Kelvin scale is defined and how it differs from other temperature scales.
  • The Kelvin scale is the base unit of temperature in the International System of Units (SI). It is an absolute temperature scale, where the lowest possible temperature, absolute zero, is defined as 0 Kelvin. This differs from the Celsius and Fahrenheit scales, which use arbitrary starting points. A change of 1 Kelvin is equivalent to a change of 1 degree Celsius, but the Kelvin scale starts at absolute zero, which is -273.15 degrees Celsius. The Kelvin scale is used to measure the absolute temperature of a system, providing a scale that is independent of the properties of any particular substance.
• Describe the relationship between the Kelvin scale and the concept of thermal equilibrium.
  • Thermal equilibrium is a state where two or more systems or parts of a system are at the same temperature, meaning there is no net flow of thermal energy between them. The Kelvin scale is used to measure the absolute temperature of a system, which is a key factor in determining whether thermal equilibrium has been achieved. When two systems are at the same Kelvin temperature, they are considered to be in thermal equilibrium, and no further transfer of thermal energy will occur between them. The Kelvin scale provides an objective and universal way to assess the temperature of a system and its relationship to thermal equilibrium.
• Explain how the Kelvin scale is used in the context of the Carnot cycle, and how this relates to the maximum theoretical efficiency of a heat engine.
  • The Carnot cycle is an idealized thermodynamic cycle that is used to determine the maximum theoretical efficiency of a heat engine. This cycle consists of two isothermal processes and two adiabatic processes, and the Kelvin scale is essential in its analysis. The Kelvin scale is used to measure the absolute temperatures of the heat source and the heat sink in the Carnot cycle. The efficiency of the Carnot cycle is directly related to the difference between the high and low temperatures, expressed in Kelvin. By using the Kelvin scale, which starts at absolute zero, the Carnot cycle can provide a theoretical upper limit on the efficiency of any heat engine, regardless of its design or operating principles.

Related terms

Absolute Zero: Absolute zero is the lowest possible temperature, at which the thermal motion of atoms and molecules reaches its minimum. It is defined as 0 Kelvin, or -273.15 degrees Celsius.

Thermal Equilibrium: Thermal equilibrium is a state where two or more systems or parts of a system are at the same temperature, meaning there is no net flow of thermal energy between them.

Carnot Cycle: The Carnot cycle is an idealized thermodynamic cycle that consists of two isothermal processes and two adiabatic processes, used to determine the maximum theoretical efficiency of a heat engine.