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Temperature and Heat

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Temperature and Heat - Lesson Summary

Heat: A form of energy that flows from a hotter body to a colder body when they are in thermal contact.
Thermal Equilibrium: When two bodies are in thermal contact and at the same temperature, due to no net exchange of heat, then they are said to be in thermal equilibrium.
 The physical quantity that is the same for the systems in Thermal equilibrium is “temperature”.
 The SI unit of heat is “joule” and temperature is “kelvin”
Heat is defined as a form of energy that flows from a hotter body to a colder body when they are in thermal contact.
When two bodies are in thermal contact and there is no net exchange of heat, then they are said to be in thermal equilibrium.
 The physical quantity that is the same for the systems in thermal equilibrium is temperature.
 The SI unit of heat is “joule” and temperature is “kelvin”.
 
Temperature is a measure the sensation of warmth or coldness of an object, felt from contact with it. This sensation of touch gives an approximate or relative measure of the temperature. Temperature is measured in different scales, including Fahrenheit (F) and Celsius (or centigrade, C). The units of the Fahrenheit and Celsius scales are called degrees and are denoted by. Swedish astronomer Anders Celsius devised the Celsius scale in 1742. He fixed the of the scale at the freezing of water, and the at the boiling of water.
Thermometer
A thermometer is used to measure the temperature of an object – it is used to find how cold or hot the object is. Galileo invented a rudimentary water thermometer in 1593. He called this device a "thermo scope".  However, this form was ineffective as water freezes at low temperatures. In 1714, Gabriel Fahrenheit invented the mercury thermometer, the modern thermometer. The long narrow uniform glass tube is called the stem of a thermometer. The small tube called the bulb, which contains mercury. Mercury is toxic, and it is very difficult to dispose it when the thermometer breaks. So, nowadays digital thermometers are used to measure the temperature, as they do not contain mercury.
Types of Thermometers
There are different types of thermometers that measure the temperatures of different things like air, our bodies, food and many other things. There are clinical thermometers, laboratory thermometers, Galileo thermometers and digital remote thermometers. Among these, the commonly used thermometers are clinical thermometers and laboratory thermometers.
Clinical Thermometer:
These thermometers are used to measure the temperature of the human body, at home, clinics and hospitals. All clinical thermometers have a kink that prevents the mercury from falling down rapidly so that the temperature can be noted conveniently. There are temperature scales on either side of the mercury thread, one in Celsius scale and the other in Fahrenheit scale.
A clinical thermometer indicates temperatures from o note a reading, place the thermometer in the person’s mouth. Since the Fahrenheit scale is more sensitive than the Celsius scale, body temperature is measured in degrees Fahrenheit only. A healthy person’s average body temperature is between.
Precautions:
Wash the thermometer before and after use with an antiseptic solution, and handle it with care.
See that the mercury levels are below the kink and don’t hold the thermometer near its bulb.
While noting down the reading in the thermometer, place the mercury level along the eye sight.
Do not place the thermometer in a hot flame or in the hot sun.
Laboratory Thermometers
These thermometers are used to measure the temperature in school and other laboratories for scientific research. They are also used in the industry as they can measure temperatures higher than what clinical thermometers can record. The stem and the bulb are longer when compared to that of a clinical thermometer. A laboratory thermometer has only the Celsius scale ranging from -10 o C to 110 o C.
Precautions:
A laboratory thermometer doesn’t have a kink.
Do not tilt the thermometer. Place it upright.
Note the reading only when the bulb has been surrounded by the substance from all sides.
Conversion
The Celsius and Fahrenheit scales are related as   .

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