Thermometer and temperature scale (Celsius, Kelvin, Fahrenheit)

Introduction to thermometers

In physics, understanding temperature is very important. Temperature tells us how hot or cold something is. We often use thermometers to measure temperature. Thermometers help us know the average energy of the particles in an object. More energy means higher temperature and vice versa.

How do thermometers work?

Most thermometers work by using a liquid inside a glass tube that expands and rises when heated, and contracts and falls when cooled. The most common liquid is mercury or colored alcohol.

When you put the thermometer into something hot, the liquid inside the thermometer heats up, causing it to expand and rise up the tube. When you put it into something cold, the liquid inside cools down, causing it to contract and fall down.

Understanding the temperature scale

Temperature can be measured on several different scales. The three most popular scales are Celsius, Kelvin, and Fahrenheit.

Celsius scale

Most countries around the world use the Celsius scale. It is based on the freezing and boiling point of water. On this scale, the freezing point of water is 0 degrees Celsius and the boiling point is 100 degrees Celsius.

To convert Celsius to other scales we use these formulas:

Fahrenheit = (Celsius * 9/5) + 32

Kelvin = Celsius + 273.15

Example:

If your temperature is 25°C, this can be converted to the following:

Fahrenheit = (25 * 9/5) + 32 = 77°F

Kelvin = 25 + 273.15 = 298.15K

Fahrenheit scale

The Fahrenheit scale is mostly used in the United States. On this scale, the freezing point of water is 32 degrees Fahrenheit and the boiling point is 212 degrees Fahrenheit. The formula for converting Fahrenheit to Celsius is:

Celsius = (Fahrenheit - 32) * 5/9

Example:

If your temperature is 77 degrees Fahrenheit, this can be converted to the following:

Celsius = (77 - 32) * 5/9 ≈ 25°C

Kelvin scale

The Kelvin scale is used mainly in scientific experiments. It starts at absolute zero, which is the coldest possible temperature. At absolute zero, particle motion stops. Zero Kelvin is -273.15 degrees Celsius.

Why are different scales used?

Different temperature scales are used depending on needs and historical reasons. Celsius is used for everyday temperature measurement because it is easy to understand and is based on the freezing and boiling point of water. Fahrenheit provides greater accuracy for everyday temperature measurement in areas where this scale is standard.

Kelvin is used in the scientific community because it is an absolute scale, meaning it starts at absolute zero and its readings are not affected by atmospheric pressure.

Practical example

• Sunny day: 25°C, which is 77°F or 298K.
• Room temperature: About 20°C, which is 68°F or 293K.
• Freezing of water: 0°C, which is 32°F or 273K.
• Boiling of water: 100°C, which is 212°F or 373K.

Conclusion

Understanding thermometers and temperature scales is important in both daily life and scientific studies. Thermometers help us measure temperature accurately, while different scales such as Celsius, Fahrenheit, and Kelvin allow us to understand and communicate these measurements effectively.

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