Question

short notes on heat in physics

Answer 1

In thermodynamics, heat is a type of energytransfer in which energy flows from a warmer substance or object to a colder one. It can be defined as the total amount of transferred energy excluding any macroscopic work that was done and any transfer of part of the object itself.[1][2][3][4][5][6] Transfer of energy as heat can occur through direct contact, through a barrier that is impermeable to matter (as in conduction), by radiationbetween separated bodies, by way of an intermediate fluid (as in convective circulation), or by a combination of these.[7][8][9] By contrast to work, heat involves the stochastic (random) motion of particles (such as atoms or molecules) that is equally distributed among all degrees of freedom, while work is confined to one or more specific degrees of freedom such as those of the center of mass.

Since heat (like work) is a quantity of energy being transferred between two bodies by certain processes, neither body "has" a definite amount of heat (much like a body in itself doesn't "have" work). In contrast, a body indeed has properties (state functions) such as temperature and internal energy. Energy exchanged as heat during a given process changes the (internal) energy of each body by equal and opposite amounts. The sign of the quantity of heat indicates the direction of the transfer, for example from system A to system B; negation indicates energy flowing in the opposite direction.

Answer 2

TERM HEAT IN PHYSICS

Heat is a type of energy transfer in which energy flows from a warmer substance or object to a colder one. It can be defined as the total amount of transferred energy excluding any macroscopic work that was done and any transfer of part of the object itself.

Five dictionary style definitions of temperature were given. They were:

- The degree of hotness or coldness of a body or environment.

- A measure of the warmth or coldness of an object or substance with reference to some standard value.

- A measure of the average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale.

- A measure of the ability of a substance, or more generally of any physical system, to transfer heat energy to another physical system.

- Any of various standardized numerical measures of this ability, such as the Kelvin, Fahrenheit, and Celsius scale.

Although heat flows spontaneously from a hotter body to a cooler one, it is possible to construct a heat pump or refrigeration system that does work to increase the difference in temperature between two systems. In contrast, a heat engine reduces an existing temperature difference to do work on another system.

The standards-based unit of heat in the International System of Units (SI) is the joule (J). Heat is measured by its effect on the states of interacting bodies, for example, by the amount of ice melted or a change in temperature.

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