18.3
温度計と温度スケール
温度に一貫して再現可能に依存する物理的特性は、温度計の基礎として使用できます。 たとえば、ほとんどの物質では温度とともに体積が増加します。 この特性は、一般的なアルコール温度計とオリジナルの水銀温度計の基礎となっています。 温度の測定に使用されるその他の特性には、電気抵抗、色、赤外線放射などがありま…
温度計は、物体や物体の温度を測定するために使用されるデバイスです。
温度計の最も重要なタイプのいくつかは、ガラス液型、バイメタル、デジタル、赤外線、およびガス温度計です。
温度計は、摂氏、華氏、ケルビンの3つの主要なスケールで温度を測定します。これらのスケールは、水の凝固点と沸点に基づいて設計されました。
摂氏温度スケールでは、水の凝固点はゼロと表示され、水の沸点は100とラベル付けされます。これら2つの点の間には100度の間隔があるため、摂氏スケールとも呼ばれます。
ここで、温度の単位は摂氏です。
華氏温度スケールでは、水の凝固点は32で示され、沸点は212です。このスケールの温度の単位は華氏度です。
華氏スケールの温度は、変換式を採用することで簡単に摂氏に変換できます。
ケルビン温度スケールは絶対温度スケールです。ここで、ゼロケルビンは絶対零度を示し、これは可能な限り低い温度です。
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Q1: What are the main types of thermometers used to measure temperature?
The most important thermometer types include liquid-in-glass, bimetallic, digital, infrared, and gas thermometers. Liquid-in-glass thermometers use alcohol or mercury that expands with temperature. Infrared thermometers measure radiation emission and are commonly used for body temperature measurement in the ear canal, offering greater accuracy than traditional methods.
Q2: How do alcohol thermometers work to measure temperature changes?
Alcohol thermometers rely on thermal expansion, where the liquid expands more rapidly than the glass encasing it. When temperature increases, alcohol from the bulb is forced into a narrow tube, producing a large visible change in column length for small temperature changes. This design amplifies the temperature signal for easy reading.
Q3: What is the difference between Celsius and Fahrenheit temperature scales?
On the Celsius scale, water freezes at 0 degrees and boils at 100 degrees, creating 100 equal intervals also called centigrade. On the Fahrenheit scale, water freezes at 32 degrees and boils at 212 degrees. Temperature can be converted between these scales using a mathematical conversion equation.
Q4: What does absolute zero represent on the Kelvin temperature scale?
The Kelvin scale is an absolute temperature scale where zero kelvin represents absolute zero, the lowest possible temperature. Unlike Celsius and Fahrenheit, which use arbitrary reference points based on water's freezing and boiling points, the Kelvin scale is grounded in fundamental physical principles and is essential for scientific calculations.
Q5: How are temperature scales created and standardized?
Temperature scales are created by identifying two reproducible reference temperatures, typically the freezing and boiling points of water at standard atmospheric pressure. These fixed points establish the scale's range and intervals. All three common scales—Fahrenheit, Celsius, and Kelvin—use this principle to ensure consistent, reliable temperature measurement across different thermometer types.
Q6: What physical properties can be used as the basis for thermometer design?
Any physical property that depends consistently and reproducibly on temperature can form a thermometer's basis. Common properties include volume expansion in liquids, electrical resistance, color changes, and infrared radiation emission. This variety of measurable properties explains why so many different thermometer types exist for specialized applications.
Q7: Why are infrared thermometers more accurate for measuring body temperature?
Infrared thermometers measure radiation emission, which varies predictably with temperature, providing rapid and accurate readings. When placed in the ear canal, they detect infrared radiation directly from the tympanum, avoiding contact errors. This method is more accurate than traditional alcohol thermometers placed under the tongue or armpit, which depend on thermal contact and can be affected by placement variations.