Thermodynamics: A Relationships Between Heat and Other Forms of Energy (Part 2)

Units of work

Whenever a new quantity is introduced in physics, the standard metric units associated with that quantity are discussed. In the case of work (and also energy), the standard metric unit is the Joule (abbreviated J). One Joule is equivalent to one Newton of force causing a displacement of one meter. In other words,

The Joule is the unit of work.
1 Joule = 1 Newton * 1 meter
1 J = 1 N * m

In fact, any unit of force times any unit of displacement is like a unit of labor . Some nonstandard units for work are shown below. Notice that when analyzed, each set of units is like unit of measurement times a volume unit .

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Units of Heat

SI Unit of Heat

Usually, within the System International d ‘Unites , all sorts of energy are measured in terms of joules. Notably, heat may be a sort of energy, and thus the SI unit of warmth is additionally joules (J) which are defined because the amount of energy needed to boost the temperature of a given mass by one degree. Usually, 4.184 joules of warmth energy is important to extend the temperature of a unit weight (say 1 g) of water from 0 degrees to 1 degree Centigrade .

Other Heat Units

In the cgs , heat is expressed within the unit of calories which is further said to be the warmth energy needed to extend the temperature of 1 gm of unpolluted water by one degree Celsius. Sometimes kilocalorie (kcal) is additionally mentioned as a unit of warmth where 1 kcal = 1000 cal.

Additionally, British thermal unit (BTU), which is a component of the imperial system, is additionally wont to measure or calculate heat.

For source click Here.

Sign Convention of Heat

The signs of ‘w’ and ‘q’ are associated with the interior energy change. When ‘w’ or ‘q’ is positive, it means energy has been supplied to the system as work or as heat. the interior energy of the system in such a case increases. On the opposite hand, if ‘w’ or ‘q’ is negative, it means energy has left the system as work or heat. the interior energy of the system decreases. The signs of ‘q’ and ‘w’ are:

  • Heat absorbed by the system= q positive (+)
  • Heat evolved by the system= q negative (-)
  • Work done on the system= w positive (+)
  • Work done by the system= w negative (-)
Figure (J): Thermal system of a chember. Source collected from Cambridge International A & AS level Physics Coursebook.

Isothermal Reversible Expansion Work of an Ideal gas

For source click Here.

If the gas expands reversibly, the external pressure (Pextare often replaced by one value (pp) which represents both the pressure of the gas and therefore the external pressure.

w= pdV

But now that the external pressure isn’t constant, pp can’t be extracted from the integral. Fortunately, however, there’s an easy relationship that tells us how pp changes with changing VV – the equation of state! If the gas is assumed to be a perfect gas.

And if the temperature is held constant (so that the expansion follows an isothermal pathway) the nRT term are often extracted from the integral.

The upper equation springs for ideal gases only.


So, within the end we live within the century of technology and science where the introduction of science in our daily activities has transformed our lives. during this era , we are completely hooked in to physics and that we cannot deny this fact. Physics helps us in several things like maintaining our health, transporting people and goods, providing energy constructing buildings, helping us communicate, stimulating the economy and far more. Hence, we will say that physics may be a vital think about our lifestyle and thermodynamics one among the foremost important topics in physics.

Thermodynamics is as old because the universe itself, and therefore the universe is just the most important known thermodynamic system. Mainly, it’s all about energy i.e. how energy gets used and the way it changes from one form to a different . With thermodynamics, you’ll determine how efficient things are using energy for useful purposes, like generating electricity, moving an airplane, or maybe riding a bicycle. The word thermodynamics features a Greek heritage. the primary part thermos, conveys the thought that heat is somehow involved and therefore the second part dynamics, causes you to consider things that move.

Application of First Law of Thermodynamics in Daily life

  • Light bulbs transform electricity into light energy (radiant energy).
  • One ball hits another, transferring K.E. and making the second ball move.
  • Plants convert the energy of sunlight into energy stored in organic molecules.
  • You are transforming energy from your last snack into K.E. as you walk, breathe, and move your finger to scroll up and down this page.

Application of Second Law of Thermodynamics in Daily life

  • Jet engines
  • Spark-ignition engines
  • Fossil-fueled steam power plants
  • All the refrigerators
  • Deep freezers
  • Industrial refrigeration systems
  • All types of air-conditioning and air-cooling systems
  • Heat pumps and others

Application of Third Law of Thermodynamics in daily life

  • The direct use of the Third Law of Thermodynamics occurs in ultra-low temperature chemistry and physics.
  • The applications of this law are wont to predict the behavior of various materials to temperature changes. These relationships became core to several scientific disciplines, although the Third Law of Thermodynamics isn’t directly utilized the maximum amount because the other two.

We can conclude that thermodynamics is a crucial a part of our lifestyle . The second law of thermodynamics plays the foremost important role in making our life easier( heat transfer), which relates to transfer of warmth between two mediums. There are three modes of warmth transfer: conduction, convection and radiation. The concept of warmth transfer is employed in wide selection of devices like heat exchangers, evaporators, condensers, radiators, coolers, heaters, etc. These are a number of the foremost important objects we use in our day to day life.


This Article is based on by the lecture of Dr. Md. Ismail Hosen,

Assistant Professor, Department of Biochemistry and Molecular Biology

University of Dhaka.

 Some info and pictures have been added by Author and from Wikipedia.

Reference used for info: Cambridge International AS and A Level Physics Coursebook.

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About Ferdous Ahamad Opi

A 1st year biology maven who try to conduct research using the scientific method to test the validity of a theory in a rational, unbiased and reproducible manner....... E-mail: opi.ferdous@gmail.com Minimum monthly resolution: Publish (1), Revise(4), Share (4).

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