Heat and Tempearature

Heat is a form of energy which flow from a body a higher temperature to a body of lower temperature. Here we can say heat is the cause and temperature is its effect. We have to measure the flow of heat and it can be done only with the help of temparature.

Temperature is a relative measure, or indication of hotness or coldness. A hot utensil is said to have a high temperature, and ice cube to have a low temperature. An object that has a higher temperature than another object is said to be hotter. Hot and cold are relative terms, like tall and short. We can perceive temperature by touch.

Heat transfer takes place between the system and the surrounding medium, until the body and the surrounding medium are at the same temperature.

Heat is the form of energy transferred between two systems or a system and its surroundings by virtue of temperature difference. The SI unit of heat energy transferred is expressed in joule (J) while SI unit of temperature is kelvin (K), and °C is a commonly used unit of temperature. When an object is heated, many changes may take place. Its temperature may rise, it may expand or change state.

Measurement of Temperature :

A measure of temperature is obtained using a thermometer. Many physical properties of materials change sufficiently with temperature to be used as the basis for constructing thermometers. The commonly used property is variation of the volume of a liquid with temperature.

For example, a common thermometer (the liquid-in-glass type) and Mercury and alcohol are the liquids used in most liquid-in-glass thermometers.

Thermometers are calibrated so that a numerical value may be assigned to a given temperature. For the definition of any standard scale, two fixed reference points are needed. As all substances change dimensions with temperature, an absolute reference for expansion is not available. Any way the necessary fixed points may be correlated to physical phenomena that always occur at the same temperature. The ice point and the steam point of water are two convenient fixed points and are known as the freezing and boiling points.

The two points under consideration are the temperatures at which pure water freezes and boils under standard pressure. The two important temperature scales are the Fahrenheit temperature scale and the Celsius temperature scale. The ice and steam point have values 32 °F and 212 °F respectively, on the Fahrenheit scale and 0 °C and 100 °C on the Celsius scale. On the Fahrenheit scale, there are 180 equal intervals between two reference points, and on the celsius scale, there are 100.

Properties of Fluids :



Surface energy and tension
Viscosity
Dynamic lift
Venturi meter
Torricelli's theorem
Blood flow and heart attack
Stream line flow
What is pressure ?
Pressure variation with depth
Pascal's Law


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