Heat | गर्मी

Heat

Heat- Heat is energy. Sun is the natural source of heat energy

Definition:- Heat is the form of energy which produces the sensation of hotness or coldness.

Or

Heat energy of a system is defined as the sum molecules of the body.

Heat energy is also accurately called thermal energy or simply heat.  It is a form of energy transfer among particles in a substance (or system) by means of kinetic energy. In other words, heat is transferred from one location to another by particles bouncing into each other.

In physical equations, the amount of heat transferred is usually denoted by the symbol Q.

Units of Heat-

The SI unit for heat is a form of energy called the joule (J). Heat is frequently also measured in the calorie (cal.), which is defined as "the amount of heat required to raise the temperature of one gram of water from 14.5 degrees Celsius to 15.5 degrees Celsius." Heat is also sometimes measured in "British thermal units" or Btu.

Sign Conventions for Heat Energy Transfer

Heat transfer may be indicated by either a positive or negative number. The heat that is released into the surroundings is written as a negative quantity (Q < 0). When heat is absorbed from the surroundings, it is written as a positive value (Q > 0).

A related term is heat flux, which is the rate of heat transfer per unit cross-section area. Heat flux may be given in units of watts per square meter or joules per square meter.

Measuring Heat

Heat may be measured as a static state or as a process. A static measure of heat is temperature. Heat transfer (a process that occurs over time) may be calculated using equations or measured using calorimeter. Calculations of heat transfer are based on variations of the First Law of Thermodynamics.

Example of Heat: A very hot cup of coffee is placed on the table. After a certain time we notice that both the cup and coffee are cold because the surrounding room temperature is the only 260C, Hence the heat flows from a hot cup (900C) to the surroundings. If you wait patiently for a long duration of time the coffee will be cooled to room temperature.