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Wednesday, November 30, 2011

Physical Principles Used in Our House-hold Appliances

Question: Name the house-hold appliances in your house which make use of physics principles.
Answer: The house-hold appliances in our house which make use of Physics principles are:
Electric Bell
Electric Bulb
Electric Iron
Electric Fan
Hand Pump
Pressure Cooker
Tape Recorder
Domestic Hot Water System
Looking Glass etc.

Saturday, November 26, 2011

System Of Units

The following four systems of units have been in use.
1. M.K.S. System
2. C.G.S. System
3. F.P.S. System
4. International System of Units or S.I. Units.

Please note that the M.K.S. System has been revised in 1960 and the revised system of units is known as S.I. Units. S.I. units are adopted world wide now a days.

Fundamental and Derived Units

The units of length, mass and time are called the fundamental units. These are so named because they cannot be derived from one another. Moreover, they cannot be resolved into anything more fundamental.
The units of other physical quantities which can be obtained with the help of the fundamental units are called Derived units. For example, we select meter as the unit of length, then the unit of area is square meter which is a derived unit. The unit of velocity is also a derived unit which contains the units of length and time.

Measurement and the System of Units

Physics is a Science based upon exact measurement and observation. For the record of our observations and for the comparison of our measurements with those of other we must agree on a common language, definition of the terms and a set of standards. If the length of one meter is different for different persons a customer buying 3 meters of cloth will either get more or less cloth from the different shopkeepers. Similarly, if a grocer's kilogram weight less than the standard kilogram he is considered dishonest. These two examples illustrate the necessity of having standards of various kinds for different sort of measurements. These standards are expressed in different measuring units. The fundamental units of measure in science are those for length, time and mass.

Monday, November 21, 2011

Physics and the Modern Man

As we look around us we find physics being used everywhere. All the modern facilities which we have are mostly due to the progress in physics. The inventions in physics have made our life easier. Let us a have look at some of these.
In our homes, most of the house-hold appliance make use of the basic principles of physics, such as, electric bell, electric iron, heater, electric fan, hand pump, motor, refrigerator, pressure cooker, radio, tape recorder, television, telephone, VCR etc.
Just after 30 years Bardeen, a physicist, invited the transistor now thousands of transistors can be made on single chip, having the same size as a single transistor, called integrated circuit. These integrated circuits are being used in all types of instruments and equipment such as toys, washing machines, industrial control circuits, radio, TV, VCR, robots, and computers etc. This is due to the integrated circuits that we have small radios and TVs etc.
The motor cars, aeroplanes and sea-ships which have made traveling comfortable and fast use the principles of physics in their different parts. Rockets which have made possible traveling in space work on principle of physics called law of conservation of momentum. Artificial satellites though which people of one country can watch television programs of other countries also use the principles of physics.
The basic principles of physics are being applied to study the function of human body. In medicine, physics is being applied in many ways. Heat is used in thermometry, thermography, heat therapy and Cryosurgery. The principles of electricity and magnetism are used in the instruments of ECG, short wave diathermy, electrosurgery etc.
Sound, a branch of physics, has many applications in medicine ranging from the use of the stethoscope to the use of modern ultrasonic techniques to study heart valve motion and to look at the unborn child.
The instruments, such as the microscope, opthalmoscope (used for looking into the eye), otoscope (used for looking into the ears) and endoscopes (used for viewing internal body cavities such as bladder, rectum etc.) use the basic principles of light. Lasers are used in laser surgery, holography and photocoagulation of the retina (which is useful for repairing retinal tears or holes that develop prior to retinal detachemetn).
Physicists have provided the modern man with a huge source of energy, called atomic or nuclear energy, which is being used for constructive as well as destructive purposes. For example: nuclear reactors, nuclear power plants, atomic submarines, atomic missiles, atomic and hydrogen bombs etc.
In short, physics has played an important role in our life. It is being applied in all disciplines of life. In this scientific age, a background in physics is very important even for a lay-man since the new research in physics s being done to solve our social and economic problems.

Wednesday, November 16, 2011

Period Of Modern Physics

1. Crooke discovered cathode rays in 1878. J.J Thomson showed experimentally that Cathode Rays are negatively charged particles called electrons.
2. Lorentz formulated an electron theory of matter according to which vibrating electrons should emit. Electromagnetic radiations.
3. In 1895, Rontgen discovered x-rays.
4. In 1896, Becquerel discovered x-rays.
5. Planck introduced the Quantum theory of light.
6. In 1905, Einstein published his special Theory of Relativity.
7. In 1911, Rutherford proposed a model of atom, similar to solar system.
8. In 1913, Bohr gave his atomic model which proved very helpful in explaining the atomic spectra of hydrogen.
9. Quantum and relativistic Physics have completely revolutionised our concepts in physics.
10. During the 1920 more advances were made in electronics, spectroscopy and nuclear physic..
11. 1913,
compton proved experimentally the particle nature of light.
12. 1924, de Broglie introduced wave mechanics.
13. In 1927 and 1928, Davison and G.P. Thomson proved experimentally that electrons also behave like waves.
14. In 1932,
(a) Chadwick discovered the neutron
(b) Lawrence invented Cyclotron.
15. In 1934, Joliot and his wife Iren Curie discovered artificial radio activity. Fermi and others produced artificial rodioactivity neutron capture.
16. In 1938, Hahn discovered nuclear fission which is the basis of the atomic bomb.
17. In 1949, John Bardeen invented the transistor which revolutionized the modern electronics. On this he was awarded the 1956 Nobel Prize in physics along with Walter Brattain and William Shockley.
18. In 1986, Muller and Bendoz discovered high temperature superconductivity.
19. In this modern age physicists are engaged in research in almost every field of science. This is age of group research rather than individual.

Sunday, November 13, 2011

Classical Physics Period

1. In this period physics was subdivided into mechanics, heat, sound, light and electricity.
2. The theoretical mechanics was developed by D, Alembert, Euler, Lagrange and Laplace.
3. During this period the Newtonian Mechanics was so well established that the end of physics was in sight. The physicists thought they had achieved and explained everything.
4. In the field of heat,
-- Fahrenheit developed thermometers and temperature scales.
-- Black introduced the concepts of latent and specific heats.
-- Rumford, Joule and Rowland established that heat was merely a form energy.
-- Carnot gave the idea of ideal heat engine.
-- Kelvin stated his laws of themodynamics.
5. Several physicists determined the velocity of light.
6. Young, Fresnel, Malus and Brewster did a lot of research work in the field of optics.
7. Maxwell proposed his famous electromagnetic wave theory of light.
8. In this period a lot of research work was done in the field of electricity.
(a) Electricity and Magnetism were found to be interrelated.
(b) Franklin, Cavendish and Coulomb did significant work in electrostatics.
(c) Galvani and Volta studied the field of current electricity.
(d) Faraday did a lot of research in the fields of electricity and magnetism and formulated his laws of electromagnetic induction.
9. Maxwell was the most outstanding theoretical physicist of this period. He did a lot of work in thermodynamics, electricity and magnetism.

Saturday, November 12, 2011

New Awakening In Physics

1. The period of new awakening commences with Copernics, Galelio, Kepler, Gilbert and Isaac Newton.
2. Galelio and Kepler established the fundamental ideas of modern celestial mechanics base on observations.
3. This period owes a lot to Islamic period. In this era the whole work of muslim scientists was transferred to Europe.
4. Sir Isaac Newton was born in this period. He introduced his three famous laws of motion and the law of gravitation. He invented calculus and contributed a lot to the field of optics. A Part of classical mechanics in which Newton's laws are applied is called Newtonian Mechanics.

Ancient Physics

1. Historical records show that the Ancient Babylonians and Egyptians were familiar with some of the fundamental principles of physics especially those dealing with the measurement of land and astronomy.
2. Chines were familiar with the magnetic compass.
3. Thales was aware of static electricity.
4. Pythagoras introduced the famous Pythagorean theorem.
5. Democritics explained the atomic nature of matter.
6. Aristotle, a student of Plato, wrote the first book on physics.
7. Euclid made some contribution to geometrical optics.
8. Archimedes made notable contribution to optics, mechanics, hydrostatics, hydraulics and other fields of physics. He was a great mathematician. He gave the idea of force in equilibrium. He also enunciated the principle of buoyancy of fluids known after him as "Archimedes Principle". He used this principle for testing the purity of gold used for the King's crown.

Historical Development In Physics

Physics is one of the oldest and most highly organized of all the sciences. It has great contribution to the economic developments of our world.
Physics has been in action in all ages, therefore, historically it has been divided into the following five periods.
1. Ancient Physics (3000 BC to 600 AD)
2. Physics of Islamic Ear (600 AD to 1500 AD)
3. New Awakening in Physics (1500 AD to 1700 AD)
4. Classical Physics (1700 AD to 1890 AD)
5. Modern Physics (1890 to present)

Aims Of Physics

1. To produce theories in terms of which the behavior of objects in the physical world can be described.
2. To check these theories for inconsistencies by means of experiments.
3. To make predictions from the theories about matters not yet investigated, as a means of guidance for future research.
4. To discover new ways of using the physical knowledge we have not only to provide useful applications but also to have the ways for even more fruitful investigations.

Friday, November 11, 2011

How Physics is Classified Into Diferent Subjects?

(a) The earlier divisions of physics were made on the basis of natural phenomena to which the methods of physics had been applied. These branches consisted of classical mechanics, heat, sound, optics, electricity and magnesium, etc.

(b) Sometimes the physics is classified according to the particular aspect of study of nature. Examples are particle physics, atomic physics, nuclear physics, etc.

(c) Sometimes classification is made on the basis of particular instrument or technique used as X-ray diffraction, mass spectroscopy, etc.

Thursday, November 10, 2011

Machanics, Heat, Sound, Optics, Electricity & Magnetism (Definitions)

It is that branch of physics which deals with the action of forces on matter and also with the state of rest or motion of bodies. It is generally divided into the following three parts:
It is that branch of physics in which we study the nature of heat and the physical changes brought about by raising or lowering the temperature of a body.
It is the branch of physics that deals with the origin, propagation and reception of vibrations.
It is that branch of physics which is concerned with the study of light is production, propagation, measurement and properties.
In it we study the laws governing the charges at rest and in motion and the properties accociated with the charges at rest and in motion.


Physics is a science that was already involved in many different subjects. But because of the tremendous revolutions in relativity and quantum physics that occured around 1890, it as decie to divide physics into the following two classed:

1. Classical Physics (PRE- 1890)
It is Concerned largely with macroscopic bodies, that is, with those phenomena in which the objects involved are large and can be seen with the naked eye. It includes the following subjects:
  • Mechanics
  • Heat
  • Sound
  • Light
  • Electricity and Magnetism, etc.
 2. Modern Physics
Its is concerned with the submicroscopic world, that is, with those phenomena in which the structure and the behavior of individual atoms and molecules are of prime importance. It includes the following subjects:
  • Quantum Mechanics 
  • Relativity
  • Atomic Physics
  • Nuclear Physics
  • Particle Physics
  • Electronics
  • Condensed Matter Physics (Physics of solids and Fluids)


The sciences which deal with the inanimate matter (i.e. dead matter) are called physical sciences. The physical sciences include the following subjects:
Aeronautics, etc.


The Sciences which deal with the animate and inanimate (i.e. living and dead) matter are called natural sciences.

Definition Of Physics

What is a Physics? We cannot give a one sentence answer that does justice to this question. Some typical short answers are:
1. Physics is the study of the properties of matter, energy and of their mutual relationship. It tries to explain natural phenomena in terms of fundamental principles and laws.
2. Physics deals with the structure and behaviour of matter.
3. Physics is the study of the laws of nature and their applications.
4. Physics is the body of knowledge gained from the study of natural phenomena.

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