Home Electric Power

Introduction to Electric Power:

Electricity or electric power is generated at place far away from where it is to be consumed. The electric power is transmitted over long distances at high voltage which is gradually reduced by using step down transformers to 230 V, at which it is supplied to our household. Before, the power lines are connected to the electric meter which records the units of electric power consumed, a fuse is connected. This is known as company fuse. I like to share this Basic Kinematic Equations with you all through my article.

The wires coming out of the meter are connected to a main switch. When the main switch is on, then only the house receives power. After the main switch another fuse is provided, known as the consumer’s fuse. The main switch is a double pole switch. It has iron covering. The iron covering is earthed. The switch and the meter are locally earthed. From the meter the connections are taken to the distribution board.


Elecrical power system types


There are two types of wiring system

1. The tree system

In this system, the connections are taken from the distribution board to different parts of the house, each connection resembling a branch of a tree. Each connection is taken through a fuse F. It should be noted that different connections are taken in parallel, so that when the fuse in one part blows off, the remaining parts are unaffected.


2. The ring system

The ring system consists of a ring circuit starting from the main fuse box, which contains a fuse of 30 amperes. For each appliance a separate connection starts from the live part of the ring and ends on the ring. Since the power rating of each appliance is known therefore, connecting wires of proper current capacity can be used for each appliance. This makes it less expensive. Each appliance is connected with separate fuse, so that one fuse blows off the other appliances in the same room continue to work.

Earthing

To avoid this shock from the appliance, appliance is earthed. That is, we connect the metal case of the body to the earth which is zero potential. Besides the live and neutral wires, a third known as the earth wire is also provided.

Galaxy Definition

Introduction to galaxy definition:

We always observes that there are infinite numbers of stars in the sky. The question arises hat how are the stars distributed in the space. Astronomers have found that the starts are arranged in the huge groups. These groups are called the galaxies. The stars in the galaxy are held together by the gravitational attraction between them. Here we discuss about the galaxy.


A few points about Galaxy


Generally, a galaxy is the clusters of stars in the large amount. A component of the universe that has a huge group of stars and other celestial bodies bound together by the force of gravitation is called a galaxy. Apart from stars, a galaxy also has huge clouds of gases from which the new stars are born. A galaxy may have planets, moons, asteroids, comets and another celestial bodies. The number of stars in a galaxy can range about a million to hundred of billions. It is also estimated that there are over 100 billions galaxies in the universe and astronomers are discovering more every day. The galaxy in which our sun is located is called the Milky Way galaxy or Akashganga.


Types of galaxies


Galaxies have different shapes. Based on the shapes, mainly, three types of the galaxies are there, which are  Spiral galaxies, elliptical galaxies and irregular galaxies. In a spiral galaxy the stars forms a big spiral pinwheel. The Milky Way galaxy is a spiral galaxy. In an elliptical galaxy the stars are confined mainly in ellipsoid volume. An irregular galaxy does not have any particular shape.



Conclusion to galaxy


Most of the stars of the Milky Way galaxy lie in the disc shaped region, this region is called the galactic disc. The central part of the disc is thicker and bulges on both the sides. The density of stars in the bulge is much higher than that in the outer region of the galaxy. Milky Way galaxy is a large galaxy. The diameter of the galactic disc is about 100, 000 light years and its average thickness is about 70 light years.

Electricity Generation From Water

Introduction:

Electricity can be generated from water in two methods; one is the method where we use the potential energy of the water in dams using the water wheels. The other source of energy is capturing the energy from the ocean waves. The energy generated by the water is a renewable energy, as we know that water is present abundantly in the nature and there is no consumption of water during the generation of electricity from the water. Most of the countries rely on this method that is production of electricity using water because it is a renewable energy resources and gives sustainable energy.  The energy generated by the water is termed as the hydro electricity.


Sources of electricity generation


Dams: In this case whenever a dam is built at the beginning itself the tunnels are built where the water flows and these tunnels are lined with turbines. As we let out the water to flow through these tunnels the water flows over the turbines which are lined along the tunnels.As a result these turbines rotate,and thus electricity is generated.

Ocean waves: The electricity generated from the ocean is known as ocean wave power because this energy is generated by the oceanic waves. This is the process where the tidal energy is used to generate the electricity, whenever there is a high tide on the sea shore or the oceans there is lot of energy in these waves which is converted into electricity by running of the turbines. The water from the tides is stored and then this water is left over the turbines which in turn produce the electricity.


Run of the river: This is process where the natural elevations on the rivers are made use to produce the electricity. In this case the water is made to fall on the turbines which are placed at the bottom of the elevation of the river, it can be a natural or a man made elevation on the river. Here also the turbine are used to produce the electricity.

Light Measurement

There are many different units for Light Measurements. Let’s first discuss some of them.

1. Candela (cd)- It is the unit of Lumen Measurement of a light source in a specific direction, also called as candle. This intensity is perpendicular to the direction of the surface of a black body.
2. Foot candle (fc or ftc)- It is a unit of intensity which used to measure in lumens per square foot.
3. Lux (lx)-  It is the unit of illumination which equals to one lumen/ square metre.
4. End Foot candle- This unit is a measurement which is based on the focused beam only. It is a focal beam measurement from point A to point B at one-foot distance.
5. End Lumens- This measurement is based on a spot of light.


6. Luminance- Also called as Luminous Flux which is the quantity of light leaves the lamp and measured in lumens (lm).
7. Luminous (Light Level): It is the amount of light measured on the work plane in the lighted space. Remember a work plane is an imaginary horizontal, tilted or vertical line where the tasks in the space are performed.
8. Beam Lumens- It is the total flux in that region of space where the intensity is more than 50 percent of the maximum intensity.
9. Lux- It is a metric unit of measure for illuminance of a surface. One lux = one lumen/ square meter= 0.0929 footcandles.
10. Light Level- It is the measurement of intensity on a plane at a specific location known as illuminance which is measured in footcandles.
11. Efficiency—the measure of the luminous efficiency of a radiant flux which is expressed in lumens/ watt is equals to efficiency.
12. Watt- It is a measurement of electrical power which does not relate to the output level and defines as the rate of energy consumption by an electrical device in operating stage. Watts= Volts x Amps x Power Factor (PF)



The wavelength is a length of a function period which shows the distance between any two points with the same phase and measured in meter light.  Let’s discuss; ‘How to Measure Wavelength of Light’? It can calculate either from the energy or frequency by using the speed and Planck constants. Remember the energy is typically expressed in electron volt (eV) units and the frequency is expressed in Hertz where one Hz equals 1/sec. Therefore the relation between velocity, frequency and wavelength can be written as follows;

Velocity of Light = (wavelength) x (frequency)(meters) x (cycles per second or Hertz)
= (3 x 108 m/sec)

Initial Velocity

The first question that arises when we read about distance, speed and velocity is the basic difference between speed and velocity. Velocity is the directional quantity while speed is not. We have already discussed about the importance of direction while calculating vector quantities.Having problem with Formula for Velocity keep reading my upcoming posts, i will try to help you.

Velocity in simple terms can be defined as the distance covered per unit time in a particular direction. This means that here we are also taking the direction in consideration. If we were to define speed we could have said it the distance per unit time. We will not have mentioned the direction bit.

We can divide the velocity into two parts. These are final and the initial velocity. As it is clear from the name the In. velocity is basically the starting velocity of an object or a body while final velocity is the finishing velocity. It may seem confusing at first but is quite easy.


Let us take an example. If the car starts and attains a velocity of 30 kilometers per hour then the initial vel. Considered would be zero km per hour while the final velocity will be 30 km per hour after 4 hours in a particular direction say southwards. Calculate Initial Velocity is easy. We can directly use the equation of motion which says
v = u + a t - - - - - - -(1)
Here v is the final velocity
U is the initial velocity
A is the acceleration
And t is the time taken to attain the final velocity.
Also s = u t + ½ a t 2 - - - - - - - - -(2)
Here s is the distance covered in a particular time interval.
This is the Equation for Initial Velocity. There is yet another equation for its Calculating Initial Velocity. It is:
V2 = u2 + 2 a s - - - - - - - - - - -(3)
Let us assume a ball is rolling on a platform. It attains a velocity of 10 m per seconds with an acceleration of 4 m per second 2. The time taken is 2 seconds.
Let us try to calculate the initial velocity.  Take the first equation into consideration.
So v = u + a t
10 = u + 2 * 4
10 = u + 8
u = 2
So initial vel. is  2 metre per second.
You can also calculate it according to different values of s, a, v, t in different situations.

Velocity Mass Equation

Mass in special relativity

The term mass  in special relativity usually refers to the rest mass of the object, which is the Newtonian mass as measured by an observer moving along with the object. The invariant mass is another name for the rest mass of single particles. The more general invariant mass (calculated with a more complicated formula) loosely corresponds to the "rest mass" of a "system." Thus, invariant mass is a natural unit of mass used for systems which are being viewed from their center of momentum frame, as when any closed system (for example a bottle of hot gas) is weighed, which requires that the measurement be taken in the center of momentum frame where the system has no net momentum. Under such circumstances the invariant mass is equal to the relativistic mass (discussed below), which is the total energy of the system divided by c (the speed of light) squared. I like to share this Formula for Acceleration due to Gravity with you all through my article.

The concept of invariant mass does not require bound systems of particles, however. As such, it may also be applied to systems of unbound particles in high-speed relative motion. Because of this, it is often employed in particle physics for systems which consist of widely separated high-energy particles. If such systems were derived from a single particle, then the calculation of the invariant mass of such systems, which is a never-changing quantity, will provide the rest mass of the parent particle (because it is conserved over time).
Despite the convenience that the invariant mass is the same as the total energy of the system (divided by c2) in the center of momentum frame, the invariant mass of systems (like the rest mass of single particles) is also the same quantity in all inertial frames. Thus, it cannot be destroyed, and is conserved, so long as the system is closed. (In this case, "closure" implies that an idealized boundary is drawn around the system, and no mass/energy is allowed across it).


The term relativistic mass is also sometimes used. This is the sum total quantity of energy in a body or system (divided by c2). As seen from the center of momentum frame, the relativistic mass is also the invariant mass, as discussed above (just as the relativistic energy of a single particle is the same as its rest energy, when seen from its rest frame). For other frames, the relativistic mass (of a body or system of bodies) includes a contribution from the "net" kinetic energy of the body (the kinetic energy of the center of mass of the body), and is larger the faster the body moves. Thus, unlike the invariant mass, the relativistic mass depends on the observer's frame of reference. However, for given single frames of reference and for closed systems, the relativistic mass is also a conserved quantity.Although some authors present relativistic mass as a fundamental concept of the theory, it has been argued that this is wrong as the fundamentals of the theory relate to space-time. There is disagreement over whether the concept is pedagogically useful. The notion of mass as a property of an object from Newtonian mechanics does not bear a precise relationship to the concept in relativity.

For a discussion of mass in general relativity, see mass in general relativity. For a general discussion including mass in Newtonian mechanics, see the article on mass.

Used Laser Cutting Machine

Introduction to used laser cutting machines:

First we will discuss about LASER. LASER means the Light Amplification by Stimulated Radiation and Emission. The laser beams are highly energetic and highly coherent. There are different types of laser machines, which produces laser beams such as ruby laser, helium neon laser. There are different stages of  lasers. For example, ruby laser is the three stage laser and Helium neon is a four stage laser. Let us discuss about the used laser cutting machines. Please express your views of this topic Emp Bomb Effects by commenting on blog.



Use of laser cutting machines


The laser machines cut the materials by vaporizing the material at that particular place. The laser beam is focussed on the path of the size of thick human hair. In other words we can say that the laser beams be focussed on 0.005 inch and leaving vapours and ash to exhaust. We can cut the steel sheet in a desired shape by the use of laser cutting machines.

The laser beams can cut the diamond with the very fine cut. The cutting of the diamond in the fine mode is possible due to the laser cutting machines.


Factors relating to laser cutting machines


There are some factors in the laser cutting machines. The main factors are power of the laser beams, laser focusing, speed of cut, thickness of the material which is to be cut, etc. The power of the laser cutting machine is the main factor of the machine. If the power is more, then we cut deep inside the surface and more quicker. The laser cutting machine is of 50 Watt power. We can use the power ranging between 1% to 100%. Laser machine has more power as they starts up. So we have to keep warming the laser machines. The lasers have the working area of 12 inches by 24 inches. Is this topic Physics Projectile Motion Problems hard for you? Watch out for my coming posts.


Modes of cutting through a laser


The laser cutting machine has two modes of the cutting, one is called the vector mode and the other is called the raster mode. The mode which is used for designing in the cutting is called the vector mode. Rastering mode is used for the engraving purposes. The laser head of the laser cutting machines moves back and forth to cut a picture.


Conclusion for the laser cutting machines


Laser beam should be perfectly focused before use on any material. Generally the lens of the laser cutting machines has two inches focusing length. The lenses may be shorter or longer. Longer the lenses, lesser is the accuracy. It is used to cut the wood, paper, fibre glass, diamonds, etc.

Universe Infinite Finite

Introduction to universe infinite finite:

Before the study of this topic, the first question arises that what is universe. The space in which the galaxies, black holes, solar systems, suns, moons and millions of others celestial bodies is called universe. Ancient philosophers believed that earth is the centre of the universe, around which everything else in the universe revolved. They even thought that the earth to be flat in shape. To understand the creation of the universe, we had to first learn a lot about the earth and the solar system, galaxies and so on. Here we discuss how the universe is expanding. I like to share this Electromagnetic Pulse Effects with you all through my article.


Modern theories on Universe


There are several modern theories about the beginning of the universe and its future. Now the scientists think that the big bang theory offers the best explanation about the universe. This theory was proposed when the scientists concluded that the universe is expanding. In 1920, Professor Edwin Hubble observed that the frequency of light coming from far off galaxies decreased, i.e., the frequency of the light coming from the far off galaxies showed a red shift. Professor Edwin Hubble studied these red shifts carefully and concluded as follows:

All galaxies are moving away from each other.
The speed with which any two galaxies move away from each other is directly proportional to the distance between them. This is called the Hubble’s law. The larger the distance between two galaxies, faster they move away from each other.
In other words, from the observed red shift, the frequency of light coming from the far off galaxies, Professor Edwin Hubble concluded that the universe is expanding. Thus, the universe is infinite in size.


Conclusion on universe whether it is infinite or finite


The future of the universe is totally depending on the mass of the universe. If the mass is large enough, gravitational attraction will slow down the expansion and eventually stop it. After that, the galaxies will move towards each other due to the gravitational force between them. They will merge in the one lump of the super dense material. Again, a big bang will take place and a new universe will be created. Therefore, we will have an oscillating universe.

Properties of Matter Solid

Introduction to Properties of Matter Solid:
Let us see about the properties of matter solid. Matter is prepared by molecules and atoms.  We have three states of matter. The three state of matter is differing from each other because of the difference in the magnitude in the intermolecular forces. One of the states is Solid. The solid has an exact shape and size.

Solids possess a definite shape and volume at ordinary temperature. Depending on the arrangement of atoms the properties of solid varies. Based on their internal structure, solids matter are classified into two types- crystalline and amorphous.


Types of Solids:


Based on their internal structure, solids matter are classified into two types. They are,

Crystalline
Amorphous


Crystalline Solid:

The properties are, atoms are arranged in a regular, repeated and periodic pattern in crystalline solids. This orderly arrangement of atoms resembles that of brick laying by masons. Examples of crystalline solids are diamonds, quartz, rocksalt, mica, sugar, metals, etc.

Amorphous solid:

The properties are, atoms are set in a disorderly manner in amorphous solid. The best case of an amorphous solid is glass. Other examples are plastic materials, wood, etc.


Elasticity:

An external force ‘F’ is applied on the body of mass ‘m’, the body acquire an acceleration ‘a’ such that a=F/m. Due to the change, the body may suffer a deformation. This external force is known as deforming force.

As the body is deformed, internal forces are set up within the body, which tends to bring the body back to the original shape. The force developed within the body on account of relative molecular displacement is called internal force or elastic force or restoring force.

Elasticity is the properties of the material of a body by virtue of which the body regains its original shape when the deforming force is removed. Few bodies, which do not show any tendency to recover their original shape after the removal of deforming force. Such bodies are called plastic bodies.

The property by virtue of which the body does not regain its original shape after the removal of the deforming force is called plasticity. The restoring force developed per unit area of the body is called as stress. Its unit is Nm-2. The strain produced in a body is defined as the ration of change in dimension to its original dimension. The maximum value of stress within which a body regains its original state is called elastic limit.

Hooke’s law states that within the elastic limit of the body, the stress is proportional to the strain produced.

Stress/ strain= a constant.

Using this formula, we get a constant is known as modulus of elasticity.

Table of Physical Constant

Introduction to physical constant:

A physical constant is one of the physical quantity which generally has a constant value for all mediums and all changes in the body or object and it is also assumed that the value of the physical constant is universally constant in nature as well as it is universally constant in time. The mathematical constant is different from the physical constant because in mathematics the constant has a fixed value but when we calculate it, then they do not undergoes any physical measurement of any object or system. I like to share this Equation for Average Speed with you all through my article.


Table of values of Physical Constants:

The table of physical constants is nothing but a table which has listed most of the physical constant which are used in study related to physics with their values and the respective units. The table of physical constant may contain the entire physical constant and a few constants depending on the requirements. The physical constants are also used with some of the prefixes. These prefixes must be used when defining the value of the physical constant in the table.
 

                                         Table showing some physical constants



Conclusion for the physical constants


Thus a table of physical constant can contain not only the constant names but it includes the symbol of physical constant and the value of the physical constant and the unit of the physical constant either it is SI or c.g.s. and last but not the least, the prefixes used with that physical constant. The physical constants can have the dimensions depending on the measurement taken by it and some of the physical constant exists in nature which does not have any dimension. That means, when the physical constant evolves in any system then there is a change that occurs in the system which is described in such a manner that the overall unit of the quantity is null.

Teach High School Physics

Introduction to teach high school physics:
High school is the stage when the student is in tenth standard. When the student is in tenth standard, it is the first time when the student is giving the boards examination first time. Therefore, this stage is very important regarding the studies. Let us discuss that what are the important and marks scoring topics in the physics so that the student gain the very good marks.

Teaching of high school physics

Let us discuss the important topics of the physics at the high school standard which are marks scoring. The very first important and the interesting topic is optics. It is the branch of physics in which we deals about the reflection, refraction, dispersion of light. This is the geometrical optics, which we study in the high school. As we see our image in the mirror it is the example of reflection. As we see the coin inside the water it is the example of refraction. As the light passes from the prism it splits in the seven colors, it is the example of dispersion. Microscopes, telescopes, human eye and the defects of the vision also study in the high school physics. The second main topics are the electricity. In the electricity we deals with the current, resistance, ohm’s law, resistivity, temperature dependence of the resistance, series and the parallel combination of the resistances. The amount of the electric energy consumed, power loss are the topics, which are read in the high school physics. The main part of the electricity is electromagnetism and the electromagnetic induction, in which we study about the principle and working of the generator, we study about the Faraday’s law of electromagnetic induction, Lenz’s law, right hand rule, left hand rule and the screw rule. After that, we have to study about the sources of energy and the universe and solar system. These last topics are very easy as compared to the early ones. Having problem with The Shorter the Wavelength of Visible Light the keep reading my upcoming posts, i will try to help you.

Conclusion for teaching high school physics

Here from the above discussion we can conclude that the topics, which are read in the high school, are the base of the intermediate standard. So it is advised to study the high school physics with the great interest and in detail so there is no difficulty in the further studies.

Three Types of Deserts

Introduction to deserts:

A landscape that receives a very low amount of rainfall is called as Desert. Deserts are the areas with average annual precipitation of less than 250 millimeters (10 in) per year, or as areas where more water is lost by evapotranspiration than falls as precipitation. Desert is the place where plants can’t grow because of the low rainfall. Let us see some main classifications of desert. I like to share this Kinematics Problems with you all through my article.



Monsoon deserts

The word ‘Monsoon’ derived from the Arabic word ‘season’. Because of the drastic changes in the temperature between the continents and the oceans, Monsoons are developed. The southeast wind of the Indian Ocean leads heavy summer rains in India mostly in coastal regions. When the monsoon crosses India, it loses its moisture on coastal Aravalli Range. The Thar Desert of India and pakistan is the part of a monsoon desert region west.


Polar deserts:


Polar deserts are rich in rain fall and it has precipitation per year is less than 250 millimeters and a mean temperature is less than 10° C. In the world, polar deserts totally cover 5 million square kilometers. Sand dunes are not important features in these types of deserts while snow dunes are usually occurs only in low rain fall areas. Please express your views of this topic Permanent Magnet Definition by commenting on blog.


Hot and Dry deserts:


Hot deserts are usually present around the equator. Hot and dry deserts are warm around the year and very hot in the summer. And it has low humidity. It has little rain fall in winter. Very Small but heavy storms are occurs often. The Soil presents in this type of desert is too hard and rocky. Burrowing mammals, insects and reptiles are the main creatures living there. The Sandy Desert of Australia, the Sahara of North Africa (largest desert in the world) the Sonoran Desert of Arizona and northwestern Mexico fall under this category.

Issac Newtons Law

ISSAC NEWTON'S LAW

About Sir Isaac Newton’s:

Sir Isaac Newton’s was one of the greatest scientists and mathematicians that ever live. He was born in England on December 25th, 1643. He was born the similar year that Galileo died. He lived for 85 years.

Isaac Newton was raise by his grandmother. He attends Free Grammar School and then went on to Trinity College Cambridge. Newton work his way through college. While at college he becomes interested in math, physics, and astronomy. Newton usual both a bachelors and masters degree. I like to share this newton's law of cooling equation with you all through my article.



Newton’s First Law of motion:

An object at rest will stay at relax unless acted on by an unequal force. Objects in motion continue in motion with the same speed and in the same speed and in the same direction unless acted upon by an unequal force.

This law is often called "the law of inertia".

This means that there is a natural propensity of objects to keep on doing what they're doing. All objects stand firm changes in their state of motion. In the absence of an unequal force, an object in motion will

Keep this state of motion.


Newton’s Second Law of motion:


When a force acts on a mass the acceleration is produced.The greater the mass (of the object being accelerated) the larger the amount of force needed (to accelerate the object).

Everyone automatically knows the Second Law. Everyone knows that heavier objects need more force to move the same distance as lighter objects.

But, the Second Law of motion gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation:

F = M X A
or
FORCE = MASS times ACCELERATION


Newton’s Third Law of motion:


The Newton’s third law is, meant for every action there is an equal and opposite re-action.This means that for each force there is a reaction force that is equal in size, but opposite in direction. That is to say that at any time an object push another object it gets pushed back in the opposite direction equally hard.

Sir Isaac Newton Science

Sir Isaac Newton Science

Sir Isaac Newton was an English physicist, mathematician, and astronomer, who is widely considered as one of the most influential people in human history. His 1687 publication of the Philosophiæ Naturalis Principia Mathematica (usually called the Principia) is considered to be among the most influential books in the history of science, laying the groundwork for most of classical mechanics. In this work, Newton described universal gravitation and the three laws of motion which continues an important role in the scientific view of the physical universe for the next three centuries. Newton also built the first practical reflecting telescope and developed a theory of colour based on the observation of a prism. He also formulated an empirical law of cooling and studied the speed of sound. I like to share this heat capacity equation with you all through my article.



Sir Isaac Newton's Science:


Newton investigated the refraction of light, demonstrating that a prism could decompose white light into a spectrum of colours, and that a lens and a second prism could do the reverse.

His studies proved that coloured light does not change its properties by separating out a coloured beam and shining it on various objects. Newton noted that regardless of whether it was reflected or scattered or transmitted, it stayed the same colour. Thus when objects interact with already-colored light, colour is produced. This is known as Newton's theory of colour. From this work, he concluded that the the dispersion of light into colours can be seen in lens of any refracting telescope. Newton’s contribution to the Law of Gravity is phenomenal and is regarded one of the major break-throughs in the world of Science.



Sir Isaac Newton’s Laws of Motion:


The famous three laws of motion are:

Sir Isaac Newton's First Law (also known as the Law of Inertia) states that an object at rest tends to stay at rest and that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force.

Sir Isaac Newton's Second Law states that an applied force on an object equals the rate of change of its momentum, with time.

Sir Isaac Newton's Third Law states that for every action there is an equal and opposite reaction

Meaning of Physical Science

The term physical science may often be misinterpreted to be a particular branch of science. It is actually a term used to group the different branches of natural science that study non living systems. In this context, physical science may seem different from biological science, which deals with the study of living systems. However, there is some confusion that the use of the term physical science creates, because while it deals with non living systems, some of these systems also deal with biological phenomena. There are different branches that come under the aegis of physical science. These include astronomy, physics, chemistry, geology, oceanography, hydrology, meteorology, and soil science. Physical science is based on the different theories and propositions made to explain the different aspects of behavior of nature. I like to share this The Electromagnetic Spectrum Includes with you all through my article.

There have been a number of reputed scientists who have worked in the sphere of physical science, both from ancient and modern times. Eminent people from the ancient times in this field include Aristotle, Archimedes, Robert Boyle, Francis Bacon, Galileo, Nicolaus Copernicus, Thales of Miletus, etc. From the modern times, scientists who worked in this field include Marie Curie, Albert Einstein, James Hutton, Isaac Newton, Linus Pauling, etc.
Science (from the Latin scientia, meaning "knowledge") is a systematic enterprise of gathering knowledge about the world and organizing and condensing that knowledge into testable laws and theories.As knowledge has increased, some methods have proved more reliable than others, and today the scientific method is the standard for science. It includes the use of careful observation, experiment, measurement, mathematics, and replication — to be considered a science, a body of knowledge must stand up to repeated testing by independent observers. The use of the scientific method to make new discoveries is called scientific research, and the people who carry out this research are called scientists.This article focuses on science in the more restricted sense, what is sometimes called experimental science. Applied science, or engineering, is the practical application of scientific knowledge. Having problem with Doppler Shift Formula keep reading my upcoming posts, i will try to help you.


A scientific hypothesis is an educated guess about the nature of the universe, a scientific theory is a hypothesis which has been confirmed by repeated observation and measurement. Scientific theories are usually given mathematical form, and are always subject to refutation if future experiments contradict them.

Magnetic Field Moment

Introduction to magnetic field moment:

Magnetic moment is a determination of its propensity to align through magnetic field. Equally the magnetic moment also magnetic field might be measured towards vectors which contains a magnitude and the direction. The way of the magnetic moment point as of the south within the way of north pole of a magnet. Magnetic field created through a magnet is relative toward its magnetic moment. I like to share this Effective Magnetic Moment with you all through my article.


Magnetic field moment


For instance, circles of electric current, an electron, a tavern magnet, also planet all contain magnetic moments.

Further accurately, the word magnetic moment usually refers toward a system magnetic dipole moment, which it is; create the initial word within the multiple extension of a common magnetic field. Dipole part of object's magnetic field be symmetric on the way of magnetic dipole moment, also reduce like the inverse dice of the distance as of the object.

Magnetic moment of solenoids:

Magnetic moment of a number of turn solenoid is resolute when the vector total of the instant of entity rotates. In the case of the same rotation, it is equivalent just towards the entity that turns instant multiply through the whole number of rotation within the solenoid. Formerly, the value of sum magnetic instant is established, it will be used to create the distant field also to store energy within the outside field and within the similar approach like used for the single-turn circle. Having problem with Centripetal Acceleration Equation keep reading my upcoming posts, i will try to help you.

Type of magnetic sources:

Motion of electric charges.
Intrinsic magnetism of elementary particles.

Magnetic dipole moment


Since the term used for the torque lying on an existing circle, the uniqueness of the existing loop be summarized within its magnetic instant.

`mu=IA`

Magnetic instant be able to be measured toward exist a vector quantity through the way vertical to the current circle within the right-hand-rule way.

Torque is known through,

`tau=muxB`

When we see within the geometry of an existing circle, this torque be inclined to line up the magnetic instant through the magnetic field B, thus this correspond to its lowly energy configuration. Potential energy related through the magnetic moment can be written as,

`U(theta)=-mu.B`

Thus, the distinction within energy among aligned also be anti-aligned,

`DeltaU=2muB`

Space Wave Propagation

Introduction:

Generally the space wave propagation has the following components:

Direct wave
Reflected wave
Direct wave is getting from the transmitting antenna and the reflected wave is getting from the surface of the earth.

Space waves are the waves which are used for satellite communication and line of sight path. The waves have frequencies up to 40 MHz provides essential communication and limited the line of sight paths. Having problem with vector equation keep reading my upcoming posts, i will try to help you.


propagation of space waves:


The output signal which is received from the receiving antenna depends on the phase difference among the direct and reflected rays. The earth cause the reflection of phase difference of 1800. If the differences between the antennas are not too long then the direct and reflected waves which are arriving at the receiving antenna oppose the phase which cancelling each other.

By raising the heights of antennas space waves becomes more effective. The transmission of direct waves is not straight always. It may be refracted on the earth’s surface. Is this topic Regions of the Electromagnetic Spectrum hard for you? Watch out for my coming posts.


Antenna for space propagation:


Antenna:

One of the important components of the space wave propagation is antenna. It is located at both sides of the transmitter and receiver.

The transmitting antenna radiates the electromagnetic waves and the receiver antenna gets the transmitted signal from transmitting antenna. The antenna is acts as a conversion device.

Process of transmitting antenna: Converts the electrical energy into electromagnetic energy

Process of receiving antenna: Converts the electromagnetic energy into electrical energy

Normally the length of the antenna is `lambda/4` . Here the wavelength of radio frequency is `lambda`.


Television signals:


Television signal propagation:

The frequency range of Television signal is from 88MHz to 960 MHz.

Possibilities for transmitting TV signals:

With the help of satellite for communication which can reflect the signals back to earth
With the help of very height antennas
Coverage range: The TV signals can cover the range of d=`root()(2R_eh)` where h is the height of antenna

This covering range of TV signals is increased by increase in height of antenna.

Uniform Motion

Introduction to Uniform Motion

A motion is said to be uniform if the particle covers equal distances in equal intervals of time, however  small these intervals of time may be , always in the same direction. Strictly speaking , no motion is uniform.

When a particle has uniform motion, neither the magnitude nor the direction of velocity changes , so the velocity is constant in uniform motion and is equal to Instantaneous velocity of the particle. I like to share this equation for frequency with you all through my article.

So uniform is a relative concept. If an object A is in uniform motion relative to another object B, then from B's view there appear to be no force applied to A; i.e. it appears to be neither accelerating nor decelerating, nor changing directions or moving in a curve. The same should apply vice versa.

when a particle possess uniform motion, it's velocity- time graph is a straight line parallel to time axis.If the velocity of the particle is taken as positive, the straight line is taken above the time axis and if it is negative, then the V-t graph will be a straight line below the time axis


Uniform Motion : Velocity- time Graph


The Velocity- time graph for uniformly accelerated rectilinear motion is straight line sloping upwards.

The velocity- time graph for a uniformly retarded motion is a straight line sloping downwards.

Let us consider a particle moving with constant acceleration .If U and V be the velocities at time t1 and t2  respectively, then

`V= U+at` gives the equation connecting initial velocity, final velocity, acceleration and time. I have recently faced lot of problem while learning Effects of Radiation on Humans, But thank to online resources of math which helped me to learn myself easily on net.


Uniform Motion : V-t Graphs and Acceleration


The Velocity- time graph for the uniformly accelerated motion of a particle is a straight line sloping upwards.

The area under the V-t graph gives the distance covered by the particle.It is calculated by the equation `V^2= U^2+2ad`

so here distance is as area under Velocity- time graph

The slope of the V- t graph for uniformly accelerated motion gives the acceleration.

Laser Cutting Process

Introduction to laser cutting process:

Laser which stands for Light amplification by stimulated emission of radiation.When electromagnetic radiation or some times visible radiations  released by the stimulated emission then this is known as Lasers.Electrons present in the elements can change their state in order to attain stability.When any energy is supplied then electrons are excited to higher states,but at the higher states these are not so stable so it jumps down by releasing some energy.These energy comes under certain range .It can be in the electromagnetic range,visible range or may be in some other range of the spectrum.Laser is a monochromatic and short wavelength rays.These rays have high frequency. Is this topic Definition Kinetic Energy hard for you? Watch out for my coming posts.

Laser beams are very useful in many fields.Laser cutting is also a field where lasers are used to cut the materials.Lasers are very high power beams when it is subjected to the materials then material melts,vaporises or burns,or it is blown away by the high pressure beams.As compared to the mechanical cutting this process of cutting is very effective and accurate.Some times materials are very hard to cut by using normal mechanical methods,so in these cases laser cutting  helps and it makes the cutting very easy and simple.

Types of Laser

There are mainly three types of laser cutting device is used depending upon the material used for the production of lasers.These materials are.

1)Carbon Dioxide

2)Neodymium

3)Neodymium yttrium Aluminium garnet

These different lasers are used in different applications.These are used for cutting,trimming,scribing.engraving etc.To produce the laser beams the lasing materials are stimulated ,then the generated beam is reflected so many times internally by using mirrors till it gains high  energy  to come out as monochromatic beams.



Different Methods of Cutting by Laser

By using laser cutting of material can be done in various ways.The high energy of the beam is mainly used to cut the material.Some of the methods are described below

By vaporising-in this method the material is heated to its boiling point to obtain a gap.

Thermal stress cutting-This method is used for the brittle material .When Brittle material is subjected to high heat then it results in crack.

melt and blow-In this method first the material is melt and then it is blown by high pressure beams.

By cold cutting

Scribing

General Electric Refrigerator

Introduction to General Electrical Refrigerators:
A refrigerator is a cooling apparatus. The common name which we use is Fridge. Cooling apparatus is in the sense it is used to cool the products. Mainly it is used for the storage of food devices. This devise is used to reduce the rate of spoilage of food stuffs. The refrigerator keeps a temperature a few degrees above the freezing point of water. It is also called as Freezer. Having problem with What is Electric Charge keep reading my upcoming posts, i will try to help you.

Types of Refrigerators:

1. Absorption Refrigerator – In this quite running is required. They don’t have bulky mechanism.

2. Compressor Refrigerator – They make noticeable noise.

3. Solar Refrigerator – They are designed to reduce electrical consumption .these have advantages that they do not use refrigerants that are harmful to environment.

Non food use: They are used in laboratories, for storing samples analysis, storing film stock and morgues.

Freezer: Freezer units are used in households and in industry and commerce. Domestic freezers are generally upright units resembling refrigerators.

4. Magnetic Refrigerator – These Refrigerators work on the magneto caloric effect. The cooling effect is triggered by placing a metal alloy in a magnetic field.

Temperatures zones and rating:

Some refrigerator are having are having four zones to store different types of food.

1.  -18^0 C (-0^0 F) (freezer)

2.  0^0C (32^0 F) (meats)

3.  5^0 C (41^0 F) (refrigerator)

4.  10^0 C (50^0 F) (vegetables)

The capacity of a refrigerator is measured in either litters or cubic feet.  Typically the volume of a combined fridge-freezer.is split to 100 liters (3.53 cubic feet) for the freezer and 140 liters (4.94 cubic feet) for the refrigerator, the values are highly variable. Please express your views of this topic Temperature Formula by commenting on blog.

Features of General Electric Refrigerator:

The newer refrigerators m y includes:

A powerful failure warning

Chilled water and ice available from an indoor stations o the door need not be opened.

Automatic defrosting.

Automatic cooling at the steam

Inductors in Ac Circuits

Description of an inductor:

An inductor in a AC circuit is a component that has the property of inductance. Inductors have very wide applications. The inductance of an inductor makes the current to lag the voltage in an AC circuit and this phenomenon is used in certain applications. The inductors are also called reactors, chokes and coils depending upon the application. I like to share this formula celsius to fahrenheit with you all through my article.

The inductor is basically a closely wound coil around a material of high permeability (magnetically susceptible).

Let us study what exactly are the functions of inductors in AC circuits.

Concept of Inductance by an Inductor in Ac Circuits:

The above diagram shows a AC circuit connected to an inductor. When an AC voltage is applied to an inductor, the rate of change in current passes through that induces an emf, as per Faraday’s law. This emf, as per Lenz’s law opposes the change in current.

The inductance of an inductor is denoted by L and its unit is Henry, named after the American scientist who discovered electromagnetic induction at the same time with the great scientist Michael Faraday from England.

One unit of Hendry produces an emf of 1 volt for a change in current of 1 ampere per second. Understanding An Electric Current is Measured in Units of is always challenging for me but thanks to all math help websites to help me out.

Inductors in Ac Circuits:

Inductors in AC circuits, as explained earlier opposes the change in current. In a way it can be termed as a magnetic resistor. Like resistors, the equivalent inductance of various inductors is the sum of the values of all the inductance values when they are connected in series. That is,

L = L1 + L2 + L3 ….. + Ln

Similar to the case of resistors, in parallel operation,

(1/L) = (1/L1)+ (1/L2) + (1/L3) ….. + (1/Ln)

Like resistors in resistive circuits, the inductors in AC circuits converts the electrical energy but stores that in the magnetic field.  The energy stored is given by,

E = (1/2) LI^2

Right Angle Mirror

Introduction to right angle mirror:

Any smooth polished surface, which can return the rays of light into the same medium, is called mirror. Looking glass is the best example of mirror. Any highly polished metal surface also acts as a mirror. Still water or oil have a smooth surface and hence acts like a mirror. Even highly polished furniture or the utensils acts like a mirror. Here we discuss the right angle mirror. I like to share this equation for converting celsius to fahrenheit with you all through my article.

Right Angle Mirror

If the two mirrors are arranged so that they inclined at an angle of 90° to each other are called the right angle mirrors. Mirrors are based on the optical phenomenon called reflection. When a ray of light traveling from one optical medium to another optical medium it bounces back from the interface with the change of the angle is called reflection. We can see our image in the looking glass due to the phenomenon of reflection of the light falling on us. Now let us consider that the two plane mirrors M and N are placed at right angle to each other as shown in the diagram.

Let them intersects at point O. Now an object is placed between the mirrors. We get three images of this object. As we know that the number of images formed by the mirrors which are inclined at an angle `theta`° is given by 360 / `theta` - 1 (if 360 / `theta`  is an even number). So, we get the three images formed by this system of the mirrors.
.

Conclusion for the Right Angle Mirrors

Here we conclude that the images formed by the system of the right angle mirrors is virtual that means we cannot get these images on the screen. The size of the images is same as that the object. The image formed is laterally inverted. The system of the right angle mirrors are used in the solar cookers, kaleidoscopes, periscopes etc. Generally, we use two plane mirrors to make the right angle mirror system but in the different condition and for the several purposes we use the combination of the plane and spherical mirrors.

Speed Practice Problems

Speed of an object is defined as the distance covered by it in per unit time interval. It is obtained by dividing the distance covered by the object by the time it takes to cover that distance.

Therefore ,                                    Speed = Distance covered / Time taken

The speed practice problems can be solved by using the above formula.

Here are some of the speed practice problems:

Speed Problems

Problem:  A train crosses a pole in 15 seconds. If the length of the train is 300 meters, find the speed of the train. (Answer: 20 m/ sec).

Solution : Speed = Distance / time

Speed =  300 / 15

Speed = 20 m / sec is the answer.


Practice Problems on Speed.

Problem: Brittany walking at a speed of 20 km/h reaches her college 10 minutes late. Next time she increases her speed by 5 km/h, but finds that she is still late by 4 minutes. What the distance of the college from her house?(Answer: 10 km).

Problem: The average speed of Ryan for a 6 hrs journey is 45 km/h. If he travels with the speed of 40 km/h for the first four hours , find the average speed for the last two hrs.

Problem: X and Y are two stations 600 km apart. A train starts from X and moves towards Y at the rate of 25 km/hr. Another train starts from Y at the rate of 35 km/hr. How from X they will cross each other? (Answer: 250km)

Problem: The boat goes 15 km upstream in 80 minutes. The speed of the stream is 5 km/h. What is the speed of the boat in still water? (Answer: 16.25 km/hr)

Problem: A motorboat whose speed in still water is 15 kmph goes 30 km downstream and coves back in a total 4 hours and 30 minutes. Determine the speed of the stream. (Answer : 5 kmph)

Problem:  Alex average speed for the 5 hours is 10 miles per second. His average of the next three hours is 15 miles per hour. Find the average speed for the total 8 hours. (Answer: 11.87 miles per hour).

Demagnetization

Introduction to demagnetization:

The reverse process of magnetization in which a magnet loses part or whole of its magnetism is called demagnetization. Not only magnets or magnetized pieces of iron, but also the unmagnetised pieces of iron are constituted of molecules that themselves are magnetic character. Each molecular magnet possesses a north pole and a south pole. The reason why an unmagnetised pieces of iron does not exhibit magnetic properties although it itself is made up of magnets is that different molecular magnets form closed group so that the effect of the north pole of one of the molecular magnets on a neighbouring molecular magnet is exactly counterbalanced by the opposite pole of the other molecular magnet situated very closed to it.

Methods of Demagnetization

1.Rough handling: it is observed that if a magnet is subjected to rough treatment such as dropping from a height or hammering then it gradually loses part or whole of its magnetism.

The rough handling disturbs the alignment of some of molecular magnets so that the magnetization would become weak.

2. Heating: A magnet is found to lose its magnetism when heated. The quantity of magnetism lost would depend on the temperature to which it is heated. On heating a magnet, the internal energy of the molecular magnets increases. This results in more violent vibrations of the molecules, so that their alignment in a given direction is disturbed and the magnetization becomes weak.

Special Cases of Demagnetization

Electrical method: A long coil (solenoid) of insulated copper wire is connected to a source of alternating current. The magnet is placed inside this coil so that the magnet is along east-west direction. The current is switched on and the magnet is pulled out of the coil. When checked the magnet is found to possess no magnetism.

Self-demagnetisation: It is observed that the magnets lose their magnetism of their own accord.

Momentum Vectors

Introduction to momentum vector:

Measurement of motion of a body can be explained by momentum vector.

Definition of momentum vector:

Momentum vector is defined as the total motion contained in the body. Mathematically, momentum vector is equal to the product of mass of the body and its velocity. I like to share this Conservation of Linear Momentum with you all through my article.

P = m × v

Where m is the mass of the body and v be the velocity of the body.

Momentum vector is a vector quantity. The unit of momentum vector is kg m /s in MKS and g cm /s in CGS.

Principle of Conservation of Momentum Vector:

It states that if no external force is applied on a system, then the momentum of the system remains constant. In other words, if there is no external force applied on the system,

the initial momentum of the system will be equal to the final momentum of the system Consider a system of two bodies on which there is no external force acting on it. Because the system is isolated from the surroundings, so it interacts only due to their mutual interactions. Due to the mutual interaction, the momentum of the individual bodies may change but the total momentum of the system remains constant. If q1 and q2 be their individual momentum's, then Please express your views of this topic elastic collision formula by commenting on blog.

q1 + q2 = constant

For a system of n bodies, we can say that, q1 + q2 + q3 +…..+ qn = constant

Practical Application of Principle of Conservation of Momentum Vector:

When a bullet is fired from the gun, the gun recoils or gives a jerk in the shoulder in the backward direction. Let M be the mass of gun and m be the mass of the bullet. Initially both bullet and the gun are at rest. On firing the gun, suppose that the bullet moves with velocity v and the gun moves with velocity V. As we use the principle of conservation of momentum,

Total momentum of the gun and the bullet before firing = total momentum of the

bullet and the gun after firing

0 = MV + mv

V = - mv / M

The negative sign shows that the gun will move in the opposite direction of bullet.

Forms of Heat Transfer

Introduction to forms of heat transfer
The science of heat transfer is concerned with the estimation of the rate at which heat is transferred, the duration of heating or cooling for a certain heat duty and the area required to accomplish that duty.

There are three different forms of heat transfer : 1. conduction 2. convection 3. radiation

Conduction form of heat transfer

It is the  heat transfer between two bodies or two parts of the same body through molecules which are more or less stationary. In liquids and gases conduction results from the transport of energy by molecular motion near the wall and in solids it takes place by a combination of lattice vibrations and electron transport. The law which determines this conduction heat transfer is called as Faraday's Law. This law states that the rate of heat flux is linearly proportional to temperature gradient.

Convection Form of Heat Transfer

It is the heat transfer that occurs because of the motion of a fluid past a heated surface - the faster the motion, the greater the heat transfer.  The convection heat transfer is usually assumed to be proportional to the surface area in contact with the fluid and the difference in temperature of the surface and fluid. This is also called as Newton's law of convection. When a temperature difference produces a density difference which result in mass movement, this process is called as free or natural convection. When the mass motion of fluid is caused by an external device like a pump, compressor, blower or fan, the process is called the forced convention. Here the fluid is made to flow along the hot surface and heat is transferred from the wall to the fluid.

Radiation Form of Heat Transfer

It is the heat transfer which is the result of electromagnetic radiation emitted by a surface because of the temperature of the surface. This differs from other form of electromagnetic radiation such as radio, television, X-rays, Gamma rays which are not related to the temperature.The best example of this is the heat receiving from the sun. The laws which govern this type of heat transfer are:

a. Kirchhoff's law

b. Stefan's law

c. Stefan- Boltzmann's law

Diffraction Limited

An introduction to diffraction limited:

The ability to produce images of an optical system with the angular resolution after overcoming the imperfections of the lenses is called as diffraction Limited. The optical instruments like Telescope, Microscope and camera are said to be Diffraction Limited if they give enough accuracy. Let us discuss more on diffraction limited. I like to share this Define Emp with you all through my article.

Discussion on Diffraction Limited

In Physics this Diffraction -Limited of the instrument is independent of imperfection due to other substances. It depends only on the limit of the optical power of the instrument. Like the diffraction of the telescope does not depend on the turbulence of the atmosphere. The resolution of an instrument is proportional to the size of the object and inversely proportional to the wavelength of the observed light. For telescope of circular apertures, size of the smallest feature in an image that is diffraction limited is size of the airy disc. One more important term is there to describe this topic better is Rayleigh’s limit. Rayleigh’s limit is the telescope’s ability to separate closely situated stars. The visual Rayleigh’s limit for a 203mm aperture telescope is 0.69arc seconds. Another limit is Dawes Limit that is 0.57arc second. The accuracy of radio telescope is much higher than normal telescope because they use very long wavelength which minimize the atmospheric distortion. Please express your views of this topic Formula of Density by commenting on blog.

Techniques on Diffraction Limited

The two techniques are there for diffraction limit, they are near field technique and Far field technique.

Near field technique- The Near field technique is applied for light of less than 2 wavelength.This technique gives that information beyond Diffraction –Limit.It is used to construct very high resolution image .It is used in total internal reflectance microscopy and metamaterials.It gives better result by placing objective lens extremely close to the object.As Near field technique cannot give the image more than 1 wavelength, so it can’t use in thicker than 1 wavelength. That’s why the practical uses of this technique are rare.

Far Field Technique-This is the best technique to use for imaging objects having large wavelength. It uses in biological applications like cells. This technique usually exploit optical non-linearity in material’s reflected light to generate resolution beyond the diffraction limit.

Conclusion for Diffraction Limited

A Laser beam is also called Diffraction Limited if its beam quality is ideal. In that case the laser beam focused to a small spots is as high as possible for the given wavelength. For advice on how to measure the beam quality of your laser source, or how to optimize.

Kinetic Theory

Kinetic Theory of Matter Definition : We Define Kinetic Theory as explanation which predicts the behavior of matter or motion of its particles on certain assumptions and observations.  The Kinetic Theory of Matter considers that matter is composed of very small particles or molecules which are always in motion. The Kinetic Theory gives the difference between the three elementary states of matter. This theory assumes that the matter is composed of small particles, particles are in constant or continuous motion.
Solid matter consists of particles which are so closely packed that they can vibrate only but cannot move.  In liquid matter particles are little far from each other but still close enough that the force of attraction that it takes the shape of container. The movement of the particles in liquid is confined in the volume of liquid. In gaseous matter the particles are free to move, they are very far from each other and have large kinetic energy. I like to share this Average Kinetic Energy Formula with you all through my article.

Because of the random movement, particles (liquid and gas) collide with each other and with the walls of container.  The collision between particles takes place without any change in net energy but exchange energy among them. Hence collision is perfectly elastic.
The movement of particles decides their kinetic energy through formula: KE=½mv2, m is mass and v is velocity of particle. This kinetic energy of particles decides the thermal energy or temperature of the matter. Temperature is actually the average kinetic energy of the particles of a matter.
Transfer of heat takes place from a matter of high temperature to low temperature. High temperature particles move or vibrate with high speeds and when they collide with nearby particle of less temperature (less KE), they exchange KE to them (hence increases temperature of neighbor particles). Now these particles start vibrating or moving fast and gives energy to their neighbor particles and so on. Hence thermal energy transfers from high to low temperature. So, kinetc theory explains the flow of heat by conduction which is flow of heat-energy through a matter. I have recently faced lot of problem while learning Activation Energy Formula, But thank to online resources of math which helped me to learn myself easily on net.

Kinetic Theory of Gas says that a gas consist of large number of very small particles of same mass which move continuously and randomly with certain speed. These particles collide perfectly elastically with each other and with the walls of the container.  It explains the properties, temperature, pressure and volume of gas.
Pressure due to particles on walls=(Nm2)/(3V)
Temperature T= (m2)/(3kB)
Kinetic energy=½Nm2
is average velocity of particles, N is no. of gas molecules,V is volume, m is mass of molecules, kB is Boltzmann constant.