measurement of temperature class 9 physics

Welcome to my channel ''Lectures of Physics". This channel contains lectures of physics on class 9th, 10th, 11th and 12th in easy way. This video is about measurement of temperature class 9 physics chapter 8 thermal properties of matter. Measurement of Temperature, Thermometry, Thermometric Property, and Thermometers The measurement of temperature is one of the most important tasks in science and daily life. The measurement of temperature tells us how hot or cold a body is compared to a standard reference. We cannot depend on our senses to judge temperature accurately because our feelings of hotness and coldness are subjective. Therefore, scientists have developed accurate methods and instruments for the measurement of temperature. This process of accurately measuring temperature is known as thermometry. Thermometry is the science and technique of measuring temperature. It includes the principles, methods, and instruments used to find temperature values. The field of thermometry is based on observing how some physical property of a substance changes with temperature. These measurable properties that change regularly with temperature are called thermometric properties. A thermometric property is a physical property of a substance that changes in a definite and measurable way with temperature. Examples of thermometric properties include the expansion of a liquid, change in the electrical resistance of a metal, change in the volume of a gas, or the change in pressure of a fixed volume of gas. For example, when a liquid expands on heating and contracts on cooling, its volume becomes a useful thermometric property. The uniform and predictable change in such a property makes it possible to design accurate thermometers. A thermometer is the instrument used for the measurement of temperature. All thermometers work based on a thermometric property. The most common and simple type of thermometer used for measuring temperature in daily life and laboratories is the liquid-in-glass thermometer. This thermometer uses a liquid — such as mercury or alcohol — enclosed in a narrow glass tube. As the temperature rises, the liquid expands and moves up the tube; when the temperature falls, the liquid contracts and moves down. The scale marked on the tube allows the measurement of temperature by observing the height of the liquid column. The liquid-in-glass thermometer is widely used because of its simplicity and reliability. It consists of three main parts — a bulb, a capillary tube, and a temperature scale. The bulb contains the liquid (such as mercury or alcohol), the capillary tube allows the liquid to expand and rise, and the scale indicates the corresponding temperature values. The principle of the liquid-in-glass thermometer depends on the expansion of liquids with temperature. Liquids expand more than solids when heated, and this expansion can be accurately measured, making them suitable for temperature measurement. One of the most common types of liquid-in-glass thermometers is the mercury thermometer. A mercury thermometer uses mercury as the thermometric liquid. Mercury is a shiny, silver-colored metal that remains liquid over a wide range of temperatures, making it very useful in thermometry. The mercury thermometer was invented by Daniel Gabriel Fahrenheit in the early 18th century and became the standard for accurate measurement of temperature for many years. The mercury thermometer has several advantages. Mercury expands uniformly with temperature, does not wet the glass, and gives clear readings because of its bright appearance. Moreover, mercury conducts heat well and responds quickly to temperature changes. These properties make the mercury thermometer very precise. However, it also has limitations — mercury is toxic, and it freezes at -39°C, making it unsuitable for measuring very low temperatures. For such cases, alcohol thermometers are used instead. For more amazing lectures please subscribe our channel.    • class 9 physics chapter 7 | Properties of ...      • class 9 physics chapter 6 | Work  and ener...      • class 9 physics chapter 5 | gravitation  |...      • class 9 physics chapter 4 | Turning effect...   For more lectures of class 9th visit link below    • class 9 physics chapter 1 | physical quant...   For more lectures of class 10th visit link    • class 10 physics chapter 10 | simple harmo...   For more lectures of class 11th visit link    • Physics Class 11   For more lectures of class 12th visit link    • Physics Class 12th   #lecturesofphysics #temperature #measurementoftemperature #physics #inter physics #matric level physics #school level physics #fsc physics