Sir, Could you please explain the difference between heat and internal energy?

Hi Abhinav,

First, internal energy is not an absolute number, unless you consider the mass equivalent given by E=m*C^2. The CHANGE in the internal energy of a substance or system is the sum of the heat added to or released by the substance or system and the work done by or done upon the substance or system, give by D(E)= q - w where d(E) is the change in energy, 'q' is the heat, and 'w' is the work. This is also called the first law of thermodynamics.

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when we heat a body some of the energy will be stored in the form of internal energy(the enery due to thermal vibrations(excitations) of the molecules in that body) and remailning energy will  be used to do some work.internal energy will be stored in the form of heat.For a cyclic process internal energy of the body is equals to zero but heat energy is not equals to zero.(for ex:take a body and heat it and touch the body u will feel heat because of the internal energy .and remaining will be used to do work(w).Now again apply same amount of work(w) on the body we won''t get the same amount of heat(initially applied heat).when we touch the body we won''t feel heat .so internal energy is almost all zero.)

when we heat a body some of the energy will be stored (internal energy-when we touch it we feel the heat)in the body and remaining will be used to do some work.

main difference is internal enery  is a point fuction and heat energy is a path function.For a cyclic process internal energy equals to zero but heat energy not equals to zero.

point function;it needs two points to define it( a linear line)

path function:it need no. of points to define it(a non linear path)

internal energy:due  to thermal vibrations,kinetic energy ,potential enery,dipole moment of the molecules