Unit of Temperature

Unit of Temperature

Edited By Team Careers360 | Updated on Jul 02, 2025 04:39 PM IST

A body can either be hot or cold depending upon the amount of heat energy, and this hotness and coldness measurement of a body is known as Temperature. And the units in which temperature is measured is called unit of temperature. The thermometer is the device that is most commonly used to measure the unit of temperature.

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Unit of Temperature

SI unit of temperature:

The seven fundamental quantities whose units are fundamentally defined in physics are known as SI units. The SI unit of temperature is known as Kelvin.

So, The SI unit of temperature is called kelvin. ‘K’ is the kelvin symbol used in physics. The SI unit of temperature kelvin was named after physicist Lord Kelvin. If x is the numerical value of measured temperature then the temperature of that body in the SI unit of temperature is written as x°K

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Other Unit of Temperature:

Apart from the SI unit of temperature which is Kelvin, measured Temperature is also written in some other most common units. These common unit of temperature are:

Celsius is also one of the unit of temperature. Its denoted by °C

Fahrenheit is also one of the unit of temperature. Its denoted by ℉

Rankine is another most common unit of temperature. Its denoted by °Ra

Reaumur is another unit of temperature and Its denoted by °Re

So, these were the most common unit of temperature other than the SI unit of temperature kelvin.

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Scale Ranges of unit of Temperature:

The boiling point and freezing point of temperature is best shown with a different unit of temperature in the below table as.

Scale Factor	Celsius scale	Reaumur scale	Fahrenheit scale	Kelvin scale	Rankine scale
The boiling point of water at 1 atmosphere.	100	80	212	373.15	671.67
The freezing point of water at 1 atmosphere.	0	0	32	273.15	491.67

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Relation between the different units of temperature:

This various unit of temperature are related to each other, and if we have a temperature measurement in one unit, we can convert that measurement into another unit of temperature using the following conversions.

The SI unit of temperature Kelvin and another unit of temperature Celsius are related as °K=℃+273.15

Fahrenheit and Celsius unit of temperature are related as ℉=9/5℃+32

Rankine and Fahrenheit unit of temperature are related as °R=℉+459.67

So, By using these conversions we can convert from one unit of temperature to another unit of temperature.

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Frequently Asked Questions (FAQs)

1. What is the SI unit of temperature?

The SI unit of temperature is Kelvin. The Kelvin symbol is K. It’s the standard unit of temperature.

2. What is the common unit of temperature?

The most common unit of temperature is Celsius and its denoted by ℃ . This unit of temperature is widely used in almost every physical measurement of temperature.

3. Name the scales used to measure temperature.

The various scales used to measure temperature are listed as

Celsius is the unit of temperature. Its denoted by °C

Fahrenheit is the unit of temperature. Its denoted by ℉

Rankine is a unit of temperature. Its denoted by °Ra

Reaumur is another unit of temperature and Its denoted by °Re

and the SI unit of temperature Kelvin is also used to measure temperature.

4. What are the most common three units of temperature?

The most common three units of temperature are namely Kelvin, Celsius and Fahrenheit. and all these three units of temperature are related as ℉=95℃+32 and °K=℃+273.15

5. The SI unit of temperature is (A) mole (B) Kilogram (C) Ampere (D) Kelvin

The SI unit of temperature is Kelvin. mole is the SI unit of the amount of substance. The kilogram is the SI unit of mass. Ampere represents electric current. Hence, kelvin is the SI unit of temperature and the kelvin symbol is K. So, the correct option is (D) Kelvin.

6. What's the relationship between Celsius and Kelvin scales?

The Celsius and Kelvin scales have the same size degree, but they're offset. To convert from Celsius to Kelvin, you add 273.15. So, 0°C = 273.15K. This relationship allows easy conversion between the two scales.

7. Why do scientists prefer to use Kelvin as the unit of temperature?

Scientists prefer to use Kelvin because it's an absolute temperature scale, meaning it starts at absolute zero (the lowest possible temperature) and has no negative values. This makes it more convenient for scientific calculations and is essential in many physics equations.

8. Why does the Fahrenheit scale have such different numbers compared to Celsius?

The Fahrenheit scale was created using different reference points than Celsius. It sets the freezing point of water at 32°F and the boiling point at 212°F. This results in a smaller degree size and different numbers compared to Celsius.

9. What is the most commonly used unit of temperature in everyday life?

The most commonly used unit of temperature in everyday life is degrees Celsius (°C). It's based on the freezing point of water at 0°C and the boiling point at 100°C under standard atmospheric pressure.

10. What is absolute zero and why is it important?

Absolute zero is the lowest possible temperature, where all molecular motion theoretically stops. It's important because it serves as the starting point for the Kelvin scale and represents a fundamental limit in physics. Absolute zero is approximately -273.15°C or 0K.

11. Can temperature ever be negative on the Kelvin scale?

No, temperature cannot be negative on the Kelvin scale. The Kelvin scale starts at absolute zero (0K), which is the lowest possible temperature. Any temperature above this will always be positive on the Kelvin scale.

12. What is the triple point of water and why is it important for temperature scales?

The triple point of water is the temperature and pressure at which water can exist simultaneously as a solid, liquid, and gas (0.01°C and 611.2 Pa). It's important because it provides a precise, reproducible reference point for calibrating temperature scales.

13. How does the concept of temperature relate to the kinetic energy of particles?

Temperature is a measure of the average kinetic energy of particles in a substance. Higher temperatures indicate faster-moving particles with more kinetic energy, while lower temperatures indicate slower-moving particles with less kinetic energy.

14. Why do we need different temperature scales?

Different temperature scales serve various purposes. Celsius is convenient for everyday use, Kelvin is essential for scientific calculations, and Fahrenheit is still widely used in some countries. Each scale has its own historical and practical reasons for existence.

15. How does the concept of temperature differ from heat?

Temperature is a measure of the average kinetic energy of particles in a substance, while heat is the transfer of energy between objects due to a temperature difference. Temperature is a property of an object, whereas heat is energy in transit.

16. Why doesn't the temperature of water change while it's boiling?

During boiling, the temperature of water remains constant because all the heat energy added is used to break the intermolecular bonds and convert liquid water to water vapor. This process is called a phase change, and it occurs at a constant temperature under constant pressure.

17. How does pressure affect the boiling point of a liquid?

Pressure directly affects the boiling point of a liquid. Higher pressure increases the boiling point, while lower pressure decreases it. This is why water boils at a lower temperature at high altitudes where atmospheric pressure is lower.

18. How do we measure extremely high temperatures?

Extremely high temperatures are often measured using optical pyrometers, which detect the intensity and color of light emitted by hot objects. Other methods include thermocouples for moderately high temperatures and spectroscopic techniques for very high temperatures in plasmas or stars.

19. What is the concept of negative absolute temperature and how is it possible?

Negative absolute temperature is a concept that can occur in certain quantum systems with a finite number of energy states. It doesn't mean colder than absolute zero, but rather a state where higher energy levels are more populated than lower ones, contrary to normal thermal distributions.

20. What is the difference between heat capacity and specific heat capacity?

Heat capacity is the amount of heat energy required to raise the temperature of an object by one degree, while specific heat capacity is the heat capacity per unit mass. Specific heat capacity is an intensive property, while heat capacity is extensive.

21. How does temperature affect the speed of sound in a medium?

Temperature directly affects the speed of sound in a medium. In general, as temperature increases, the speed of sound increases. This is because higher temperatures result in faster-moving particles, allowing sound waves to propagate more quickly through the medium.

22. How do thermocouples work to measure temperature?

Thermocouples work based on the thermoelectric effect. They consist of two different metals joined together, which generate a small voltage difference when exposed to a temperature gradient. This voltage can be measured and converted to a temperature reading.

23. What is the concept of critical temperature in thermodynamics?

The critical temperature is the temperature above which a gas cannot be liquefied by pressure alone. Above this temperature, the substance exists as a supercritical fluid, where the distinction between liquid and gas phases disappears.

24. How does temperature affect the resistance of electrical conductors?

In most metals, an increase in temperature leads to an increase in electrical resistance. This is because higher temperatures cause more atomic vibrations, which interfere with the flow of electrons. However, in semiconductors, the relationship can be more complex.

25. What is the concept of temperature inversion in meteorology?

Temperature inversion is a meteorological phenomenon where a layer of warm air sits above a layer of cooler air, contrary to the normal temperature gradient in the atmosphere. This can trap pollutants near the ground and affect weather patterns.

26. What is the relationship between temperature and pressure in an ideal gas?

For an ideal gas at constant volume, temperature and pressure are directly proportional. This relationship is described by Gay-Lussac's law: P ∝ T, where P is pressure and T is absolute temperature. As temperature increases, so does pressure, and vice versa.

27. How does temperature affect the solubility of substances?

Generally, the solubility of solid substances in liquids increases with temperature. This is because higher temperatures provide more energy for breaking intermolecular bonds. However, for gases dissolved in liquids, solubility typically decreases with increasing temperature.

28. What is the concept of thermal conductivity and how does it relate to temperature?

Thermal conductivity is a measure of a material's ability to conduct heat. It's defined as the rate of heat transfer through a material per unit thickness, per unit area, per unit temperature difference. Materials with high thermal conductivity transfer heat more readily.

29. How do infrared thermometers measure temperature without contact?

Infrared thermometers measure temperature by detecting the infrared radiation emitted by an object. All objects above absolute zero emit infrared radiation, and the intensity and wavelength of this radiation are related to the object's temperature.

30. What is the relationship between temperature and phase transitions?

Temperature plays a crucial role in phase transitions. At specific temperatures (under constant pressure), substances undergo phase changes such as melting, boiling, or sublimation. These transition temperatures are characteristic properties of substances.

31. How does temperature affect the speed of chemical reactions?

Generally, higher temperatures increase the speed of chemical reactions. This is because higher temperatures mean more kinetic energy, leading to more frequent and energetic collisions between reactant molecules, which are more likely to overcome the activation energy barrier.

32. What is the concept of temperature coefficient and how is it used in various fields?

The temperature coefficient describes how a property of a material changes with temperature. It's used in various fields, such as electronics (temperature coefficient of resistance), materials science (thermal expansion coefficient), and chemistry (solubility temperature coefficient).

33. How does temperature affect the viscosity of fluids?

Generally, the viscosity of liquids decreases with increasing temperature. This is because higher temperatures increase the kinetic energy of molecules, reducing intermolecular forces and making the fluid flow more easily. However, for gases, viscosity typically increases with temperature.

34. What is the concept of thermal diffusivity and how does it relate to temperature?

Thermal diffusivity is a measure of how quickly a material can change its temperature when exposed to a temperature gradient. It's the ratio of thermal conductivity to volumetric heat capacity. Materials with high thermal diffusivity rapidly adjust their temperature to that of their surroundings.

35. How does temperature affect the speed of electrons in a conductor?

Increasing temperature in a conductor increases the average speed of electrons. However, it also increases the frequency of collisions between electrons and the lattice, which increases electrical resistance. The net effect is usually an increase in resistance with temperature in metals.

36. How does temperature affect the strength and properties of materials?

Temperature can significantly affect material properties. Generally, as temperature increases, materials become more ductile but less strong. Extreme temperatures can cause phase changes, altering crystal structures and dramatically changing material properties.

37. What is the concept of temperature gradient and why is it important in heat transfer?

A temperature gradient is a gradual change in temperature over distance. It's crucial in heat transfer because heat naturally flows from regions of higher temperature to regions of lower temperature. The steeper the temperature gradient, the faster the rate of heat transfer.

38. How does temperature affect the speed of sound in different states of matter?

In general, the speed of sound increases with temperature in all states of matter. In gases, this relationship is more pronounced. In liquids and solids, the effect is usually less significant but still present. This is because higher temperatures result in faster-moving particles, allowing sound waves to propagate more quickly.

39. What is the concept of thermal comfort and how does it relate to temperature?

Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment. It's not just about air temperature, but also involves factors like humidity, air movement, and radiant temperature. The human body's perception of comfort is complex and subjective, making it an important consideration in building design and climate control.

40. How does temperature affect the behavior of superconductors?

Superconductors exhibit zero electrical resistance, but only below a critical temperature. Above this temperature, they behave like normal conductors. As temperature decreases towards the critical temperature, the material undergoes a phase transition to the superconducting state. Research into high-temperature superconductors aims to find materials that superconduct at more practical temperatures.

41. What is the significance of the Boltzmann constant in temperature measurements?

The Boltzmann constant (k) relates the average kinetic energy of particles to temperature. It's crucial in statistical mechanics and thermodynamics, providing a link between the microscopic behavior of particles and macroscopic temperature measurements.

42. How do thermometers measure temperature?

Thermometers measure temperature by utilizing materials that have predictable physical responses to temperature changes. For example, mercury expands as it heats up, allowing us to read temperature on a calibrated scale. Digital thermometers often use thermistors, which change electrical resistance with temperature.

43. What is thermal equilibrium and how does it relate to temperature?

Thermal equilibrium is the state where two objects in contact have reached the same temperature, and there's no net heat transfer between them. It's fundamental to understanding temperature as a measure of the average kinetic energy of particles.

44. What is the difference between intensive and extensive properties in thermodynamics, and how does temperature fit in?

Intensive properties don't depend on the amount of substance, while extensive properties do. Temperature is an intensive property - it doesn't change based on the amount of a substance. For example, half a cup of 100°C water has the same temperature as a full cup.

45. How do we define temperature on a molecular level?

At the molecular level, temperature is defined by the average kinetic energy of the particles. Higher temperatures mean faster-moving particles with more kinetic energy, while lower temperatures indicate slower-moving particles with less kinetic energy.

46. What is the zeroth law of thermodynamics and how does it relate to temperature?

The zeroth law of thermodynamics states that if two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This law essentially defines temperature and allows us to use thermometers to measure it.

47. How do we measure extremely low temperatures?

Extremely low temperatures are measured using specialized techniques like gas thermometry, magnetic thermometry, or noise thermometry. These methods can measure temperatures very close to absolute zero, where conventional thermometers don't work.

48. How does the human body regulate its temperature?

The human body regulates its temperature through a process called thermoregulation. This involves mechanisms like sweating to cool down, shivering to warm up, and adjusting blood flow to the skin. The body aims to maintain a core temperature around 37°C (98.6°F).

49. What is the concept of thermal expansion and how does it relate to temperature?

Thermal expansion is the tendency of matter to change its shape, area, and volume in response to a change in temperature. As temperature increases, most materials expand because the kinetic energy of their particles increases, causing them to occupy more space.

50. How does the concept of temperature apply to gases in space?

In space, the concept of temperature becomes more complex due to the extremely low density of particles. Temperature in space is often defined in terms of the kinetic energy of the few particles present, rather than by traditional thermodynamic definitions.

51. What is the concept of thermal equilibrium time and why is it important in temperature measurements?

Thermal equilibrium time is the time it takes for a measuring device to reach the same temperature as the object being measured. It's important because accurate temperature measurements can only be made once thermal equilibrium is achieved.

52. How does the temperature of the universe change over time?

The overall temperature of the universe has been decreasing since the Big Bang. As the universe expands, it cools. The current average temperature of the universe, as measured by the cosmic microwave background radiation, is about 2.7 Kelvin.

53. What is the concept of color temperature in lighting and how does it relate to actual temperature?

Color temperature in lighting refers to the apparent warmth or coolness of light. It's measured in Kelvin, but doesn't represent actual temperature. Instead, it describes the color of light emitted by a black body radiator at that temperature. Lower values (2700-3000K) appear warm, while higher values (5000K+) appear cool.

54. How does temperature affect the efficiency of solar panels?

Solar panel efficiency typically decreases as temperature increases. This is because higher temperatures increase the electrical resistance in the solar cells, reducing their ability to convert light into electricity. This is why solar panels often perform better in cooler, sunny conditions than in hot environments.

55. What is the concept of thermal radiation and how does it depend on temperature?

Thermal radiation is electromagnetic radiation emitted by all objects above absolute zero temperature. The intensity and wavelength of this radiation depend strongly on the object's temperature. As temperature increases, the total amount of radiation emitted increases, and the peak wavelength of emission shifts to shorter wavelengths.