Temperature and its measurement | Jamb(UTME)

Concept of Temperature

1. Temperature is a measure of how hot or cold an object is.
2. It indicates the average kinetic energy of the particles in a substance.
3. Higher temperature means particles are moving faster.
4. Temperature does not depend on the amount of substance—it is an intensive property.
5. It is different from heat, which is the total energy transferred between substances due to a temperature difference.
6. Temperature determines the direction of heat transfer (hot to cold).
7. Common units of temperature are Celsius $(°C)$, Kelvin $K$, and Fahrenheit $(°F)$.
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Thermometric Properties

8. A thermometric property changes in response to temperature and is used in measuring it.
9. Examples include the expansion of liquids, changes in electrical resistance, and changes in gas pressure.
10. Mercury and alcohol expand uniformly with temperature and are used in thermometers.
11. Gases show changes in pressure or volume with temperature, used in gas thermometers.
12. The electrical resistance of metals increases with temperature, which is the basis of resistance thermometers.
13. Radiation intensity, which increases with temperature, is used in pyrometers.
14. Thermometric properties must be reproducible and measurable for accurate readings.
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Calibration of Thermometers

15. Calibration ensures a thermometer provides accurate readings by comparing it to standard reference points.
16. The fixed points commonly used are the melting point and boiling point of water.
17. The lower fixed point is 0°C, the melting point of ice at standard atmospheric pressure.
18. The upper fixed point is 100°C, the boiling point of water at standard atmospheric pressure.
19. The space between the fixed points is divided into equal intervals for the scale.
20. Calibration ensures that the thermometer is accurate and consistent.
21. Errors in calibration can lead to incorrect temperature readings.
22. Digital thermometers are pre-calibrated using electronic systems for precision.
23. Regular recalibration is necessary for devices used in critical applications like laboratories and industries.
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Temperature Scales: Celsius and Kelvin

24. The Celsius scale is based on the freezing point (0°C) and boiling point (100°C) of water.
25. Celsius is commonly used in everyday life and weather reporting.
26. The Kelvin scale starts at absolute zero, the lowest possible temperature.
27. Absolute zero (0 K) is the point where particles have minimum energy and cannot move.
28. The Kelvin scale is the SI unit of temperature and is widely used in scientific research.
29. The relationship between Celsius and Kelvin is:
    
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    $K = °C + 273.15$
30. Kelvin does not use degrees; temperatures are simply written as $300K$, not $300^\circ{K}$.
31. Kelvin is essential in physics because it relates directly to absolute energy levels.
32. Negative temperatures do not exist on the Kelvin scale but are possible on the Celsius scale.
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Types of Thermometers

33. A liquid-in-glass thermometer uses mercury or alcohol that expands with temperature.
34. Mercury thermometers are accurate but are being replaced due to mercury's toxicity.
35. Alcohol thermometers are safer and can measure lower temperatures than mercury thermometers.
36. Digital thermometers use electronic sensors for quick and accurate readings.
37. Bimetallic strip thermometers use metals with different expansion rates to measure temperature.
38. Gas thermometers measure temperature by observing the pressure or volume changes of gas.
39. Resistance thermometers (RTDs) measure temperature based on the change in electrical resistance of a metal.
40. Thermocouples measure temperature by detecting voltage changes at the junction of two metals.
41. Infrared thermometers measure temperature from the thermal radiation emitted by an object.
42. Clinical thermometers are used to measure human body temperature and have a range around 35°C to 42°C.
43. Pyrometers measure very high temperatures, like those in furnaces.
44. Maximum-minimum thermometers record the highest and lowest temperatures over a period.
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Conversion Between Temperature Scales

45. To convert from Celsius to Kelvin:
    
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    $K = °C + 273.15$
46. To convert from Kelvin to Celsius:
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    $°C = K - 273.15$
47. Conversions are straightforward since Celsius and Kelvin scales are linear.
48. The freezing point of water is $0^\circ C = 273.15K$.
49. The boiling point of water is $100^\circ C = 373.15 K$.
50. Kelvin is often used in science because it simplifies calculations involving absolute energy.
51. Temperature conversions help compare readings from different types of thermometers.
52. Celsius and Kelvin scales are widely used internationally, making conversions essential.
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Practical Applications

53. Thermometers are used in weather forecasting to measure air temperature.
54. Clinical thermometers help monitor health by measuring body temperature.
55. Industrial thermometers ensure accurate temperature control in manufacturing processes.
56. Infrared thermometers are used in cooking, medical diagnostics, and measuring surface temperatures.
57. Thermocouples are widely used in industries for monitoring furnace and engine temperatures.
58. Resistance thermometers are used in scientific experiments requiring high precision.
59. Pyrometers measure high temperatures in steel plants and glass factories.
60. Temperature scales allow for consistent reporting in meteorology, science, and industry.
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Importance of Calibration

61. Proper calibration ensures the reliability of thermometer readings.
62. Incorrectly calibrated thermometers can lead to errors in medical diagnoses or industrial processes.
63. Calibration accounts for variations in thermometer materials or usage conditions.
64. Standardized calibration practices are essential for international consistency.
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Special Considerations

65. Digital thermometers are less prone to human error compared to liquid thermometers.
66. Liquid-in-glass thermometers must be handled carefully to avoid breakage or mercury spills.
67. Alcohol thermometers are preferred in cold regions because alcohol remains liquid at lower temperatures.
68. Infrared thermometers can measure temperature without direct contact, making them ideal for hazardous or inaccessible areas.
69. Kelvin is the preferred scale in physics because it avoids negative values and relates directly to energy levels.
70. Understanding temperature scales and conversions is crucial for interpreting scientific data and everyday applications.
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