Wrought iron

Cast Iron

Pig iron along with scrap iron, coke and limestone is melted in a vertical furnace called cupola. Here also the carbon and other impurities present oxidise in presence of a little amount of air, to form slag. The molten iron obtained from cupola furnace can be cast into moulds. It is, therefore, known as cast iron. It consists of 93-94% Fe, 2-4% carbon and a little of S, P, Si and Mn impurities. It is vary hard and brittle. It is cast into covers of manholes, drain-pipes, frames of machines etc.'

Wrought Iron
Wrought iron is the purest form of iron containing not more than 0 • 2 peri jnt carbon and 0-3 percent of other impurities, i.e., sulphur, phosphorus, silicon and manganese.

Manufacture
It is obtained from cast iron by removing the major portion of its impurities by the well known puddling process. The cast iron along with some scrap iron is heated on the hearth of a reverberatory furnace lined with haematite. Fe₂0₃. The hot gases and flames reflected from the roof of the furnace falls upon the charge placed on the hearth. The cast iron melts down and the molten mass is stirred or puddled at intervals by means of a long pole introduced through an inlet in the wall of the furnace. The haematite supplies the oxygen required to oxidise the carbon, sulphur, silicon, manganese and phosphorus present in the cast iron.
Carbon and sulphur are oxidised to carbon dioxide and sulphur dioxide, respectively. Silicon and manganese are oxidised to silica and manganous oxide, which combine to form manganous silicate.
3Si + 2Fe₂0₃ —* 3Si0₂ + 4Fe 3Mn + Fe₂0₃ —» 3MnO + 2Fe MnO + Si0₂ —» MnSi0₃

Slag
Phosphorus is oxidised to phosphorus pentoxide which forms ferric phosphate slag with haematite.
P₂0₅ + Fe₂0₃ —* 2FeP0₄

Slag
As the impurities are eliminated, the melting point of the metal rises and iron becomes pasty. The pasty mass is stirred which forms "balls" or "blooms" which are spongy in texture due to large amounts of slag. The balls are taken out from the furnace and the slag is squeezed out by hammering. Finally, iron is rolled into sheets or forged into bars.

Wrought iron is soft, grey, tough and can be welded. It is malleable and has a fibrous structure due to the presence of thin films of slag between layers of pure iron. The presence of slag makes it extremely tough and resistant towards rusting



and corrosion. It softens at 1000°C and melts at 1530°C. It is used to make articles which are subjected to sudden and repeated stresses such as chains, anchors, wires, bolt, agricultural implements and cores of electromagnets. It has now been largely replaced by mild steel owing to its high cost.

Metric System Chart

About Metric System:

• Metric system is an International system of measurement used commonly for measuring units in the world.
• Metric system exists in various choices of fundamental units although the choice of base units does not get affected in any form.
• Metric units are used universally in scientific work around the world for all forms of personal and commercial purposes.
• Standard set of prefixes in powers of ten are used to derive larger and smaller units from the base units.
• Goal of the metric system is to prescribe a single unit for every physical quantity so as to avoid the need for conversion factors.
• Meter is the basic unit used to measure lengths and distances. This unit is converted to many other units such as inches, feet, yards, fathoms, rods, chains, furlongs, miles, nautical miles, leagues, etc.
• Early metric system includes several fundamental or base units and other quantities are derived from the base units. For example the basic unit of speed is calculated as meters per second.
• The metric system is also called as decimal system because all multiples and sub multiples of the base units are basically factors of powers of ten.
• In a formal representation fractions are not used to represent Metric units.

Advantages of a decimal system:

• They substitute other non-decimal systems too apart from metric system of measurements.
• All derived units use a set of prefixes for each multiple such as kilo for mass (kilogram) or length (kilometer) both indicating a thousand times the base unit.

Metric System Chart

Quantity	Unit	Symbol
Length	Millimeter Centimeter Meter Kilometer	mm cm m Km
Mass	Milligram gram Kilogram Ton	mg g Kg T
Time	Second	s
Temperature	Degree Celsius	oC
Area	Square meter hectare square kilometer	m2 Ha Km2
Volume	Millimeter cubic centimeter liter cubic liter	ml cc L Cl
Speed	Meter per second Kilometer per second	m/s km/s
Density	Kilo gram per cubic meter	Km/cc
Force	Newton	N
Pressure	Kilo Pascal	K Pa
Power	Watt, kilo watt	W KW
Energy	Kilo joule, mega joule	KJ MJ
Current	ampere	A

Prefixes used in Metric System Units

Giga	G	109
Mega	M	106
Kilo	k	103
Centi	c	10-2
Milli	m	10-3
Micro	μ	10-6
Nano	n	10-9

Pig iron productions

Introduction :

Pig iron is the intermediate product which is obtained during the smelting of iron ore with coke, in this process limestone is used as flux. Pig iron has maximum carbon content, it is around 3.5–4.5% which improves the brittleness of iron. In olden days, the Chinese Zhou dynasty were making pig iron in Europe. The plant used for the pig iron production is sinter plant.There will be use of two furnaces for the pig iron production. The word pig iron comes from old casting blast furnace iron method into moulds which are arranged on the beds of sand.

Pig iron production:

Blast furnace used for pig iron production:

Pig iron production is done by blast furnace method which involves the smelting of iron ore like hematite, i.e.
Fe₂O₃ + 3CO → 2Fe + 3CO₂

A blast of preheated air is blown through the furnace which reacts with carbon which is in the form of coke to produce carbon monoxide and also a large amount of heat is produced. The produced carbon monoxide reacts with the iron ore to form molten iron and carbon dioxide. Unreacted carbon monoxide, nitrogen which is present in the blown air and hot carbon dioxide are fed into the reaction zone as a fresh feed so that there will be preheating of fresh feed using counter current gases and also there will be the decomposition of limestone to calcium oxide and carbon dioxide and starts to reduce iron oxide in the solid state. So formed calcium oxide reacts with some of the acidic impurities which are present in iron which form a slag called calcium silicate. The reactions involved in the pig iron production are

C + O₂ → CO₂
CO₂ + C → 2CO
CaCO₃ → CaO + CO₂
SiO₂ + CaO → CaSiO₃(slag)

The pig iron obtained by this method has high carbon content so which increases the brittleness by that it has limited commercial applications. If there is a need to reduce the carbon content, pig iron undergoes further processes.

Applications of Pig iron:

• Pig iron sometimes used to produce cast iron and Gray iron which is achieved by smelting the pig iron.
• Pig iron is used to produce steel metal.

Iron Steel Manufacturing

Introduction :
Iron produced in the blast furnace is known as pig iron or cast iron.  Pig iron is the iron which contains 4% of carbon and some other impurities.

Carbon contents present in pig iron are reduced by burning off carbon as carbon monoxide and carbon dioxide. Impurities present as sulphur, manganese etc are oxidised as their oxides. There are three methods of burning carbon for production of steel.

(i) Bessemer Process
(ii) Open Hearth Process
(iii) Electric Furnace Process

Bessemer Process of Manufacturing:

This was the first process for the mass-production of steel from molten iron. Henry Bessemer invented this process in 1855.

Principle: Removal of impurities from iron by oxidation is the key principle of this process. The oxidation also raises the temperature and hence melts the iron.

Process: In this process, burning takes place in a pear shaped furnace called Bessemer Converter. This furnace is coated with basic mixture of calcium oxide or magnesium oxide (CaO / MgO). Hot air is introduced through holes. The temperature of furnace is maintained at 1873K. Manganese in the iron is removed as manganese silicate, (which is called as slag).

2Mn + O₂ ----------> 2MnO

Si + O₂ -----------> SiO₂

MnO + SiO₂ -----------> MnSiO₂

Phosphorus present as impurity is removed by formation of slag. This slag is called Thomas slag. Thomas slag is very useful fertilizer.

4P + 5O₂ -----------> 2P₂O₅

3CaO + P₂O₅ -----------> (Ca)₃(PO4)₂    Thomas Slag

Open hearth process of manufacturing:

This process can be used for rapid manufacture of large quantities of steel. The steel producd by this process can be used for the construction of the high buildings. This process complemented the Bessemer process to produce steel. It is easier to control because it is a slow process.
In this process, cast iron, iron scrap, haematite and lime is taken in open hearth furnace. This furnace is heated at temperature of 1873 K. This furnace is heated with (CO+N₂). (CO+N₂) is called producer gas. Impurities are removed by oxidation with haematite.

Fe₂CO₃ + 3C ----------> 2Fe + 3CO

2Fe₂O₃ + 3S -----------> 4Fe + 3SO₂

5Fe₂O₃ + 6P ------------> 10Fe + 3P₂O₅

2Fe₂O₃ + 3Si ------------> 4Fe + 3SiO₂

3CaO + P₂O₅ ------------> Ca₃(PO4)₂ (Slag)

Electric Arc Furnace

 In this method, iron is heated electrically. Normally thesedays, steel is prepared by open hearth process. About 39% of the steel manufactured in US is produced from the electric furnace. The stel produced by this process is not very pure or of high quality.

Energy Consumption: An electric arc furnace consumes an energy of 350 - 700 kWh/ton of steel produced. We can reduce the energy consumption to 425 kWh/ton by using oxy-fuel burners.
This process is used for the electric production of steel. It is used for remelting of steel scrap. This process is useful for those markets where the quality of steel is not critical.

Air speed

Introduction :
It is the speed of an air related to the aircraft among them the qualifying airspeed are Calibrated airspeed, Indicated aircraft, Equivalent air speed, true airspeed and finally the density airspeed. This aircraft speed is measured by the airspeed indicator which is shortly and popularly known as ASI. These are connected to the pitot static system. Types of the airspeed are Indicated airspeed, Calibrated airspeed, Equivalent airspeed, True airspeed. In this article we will know types of articles and how to calculate the airspeed.

Air speed Types

Indicated airspeed is abbreviated as IAS. This indicator reads directly form the airspeed indicator by the pitot static system on the aircraft. This is the airspeed related to the CAS that is calibrated airspeed it is corrected for the installation errors and the instrument.

These IAS are very much important for the pilots for the various purposes like calculation of the limited speeds and so on. This plays an important role in the airspeed.

Calibrated air speed is for the instrument errors and position errors and the installation errors. This equation shows the installation and the minus position.
Where, Vc is the calibrated airspeed
qc is the impact pressure
Po is static air pressure. Measures 29.92126 inches Hg at sea level.
ao is speed of sound. Measures 661.4788 knots at standard sea level.

Equivalent & True airspeed

Equivalent airspeed: This produces dynamic pressure as the true speed at the altitude where the vehicle is flying. It is forward to the flight for the effects of compressibility. Compressible impact pressure makes a function of calibrated airspeed. At standard sea level equivalent airspeed and calibrated airspeed are equal.

True airspeed is also called as TAS, it is the physical speed of the aircraft. The relation between true airspped and speed is Vg.
Vt = Vg - Vw
Where Vw is the wind speed vector.
To compute true airspeed using a function of mach number
V_{t =} a_o.M`sqrt(T/(To))`
Where:
a_o= Speed of sound(661.4788 knots) at standard sea level
M = Mach number
T = Temperature in kelvins
T_o= (288.15 kelvins)Standard sea level temperature

Speed of Light and Sound

Introduction :

Light and sound are the essential part of our life and with an absence of one; we will not be able to communicate or to detect properly as we can do with help of these two. Light and sound both are the sensations produced by energetic particles with the help of which we will be able to see or listen. 

Difference between Speed of Light and Sound :

Regarding the speed of light and sound we can say the following points

1. Speed of light is much faster than the speed of sound in air.
2. Light do not require the medium to travel with its speed while the sound require medium to propagate.  
3. Speed of light is much less in transparent than what it had in vacuum.  While the speed of sound is much, fast in solid medium such as steel then in air.

Speed of light and sound : Conclusion

Why speed of sound Differ in different mediums means solid, liquid and air?

Explanation:
Since sound require medium particles to propagate properly, hence the medium having particles much closer will enhance the movement (speed) of sound wave rather than the medium which have a long gap between the particles. Since, the molecules spacing for solid, liquids, and gases are different in that gas molecules are more spread apart & free to move, liquids are a little more structured, and solids are very compact.             

The other reason for the different speed in different mediums is the elasticity of the medium. More the elasticity in the medium more will be the speeds of sound as we can understand with ball, more the elasticity of the ball more will it jump. Since steel is more elastic than air, so sound travels 19 times much faster in steel than its speed in air. E.g. if we put your ear on rail track we can hear the vibration of the train movement in the track much before than the whistle of the train which travels through air.

Aircraft speed of sound

Introduction :
Air crafts with propellers in the initial stages were not able to perform well when they approached the speed of sound. This problem resulted into deep research into jet engines conducted mainly by Frank White of England and Hans van Ohain of Germany. They carried out this research in their respective countries.

Breaking Sound Barriers

Various sources claimed to have broken the sound barriers. Claims were made that air crafts ran smoothly at the speed of sound without any turbulence but there were many disputes against these claims. These claims were made as early as 1945. Man has attempted to break the sound barriers since the time the first plane was invented by the Wright Brothers. Bell X-1 was the first flight to travel faster than the speed of sound and this happened on 14^th October, 1947 under Captain Charles Yeager.

Speed of Sound

The exact speed of sound is not known but it is considered that it varies according to the height above sea level or what we call as altitude. It is 761 mph at sea level and at 20000 feet above it is 660 mph.

Modern Aircrafts and their speed

Today there are several air crafts like fighter jets that travel at speeds faster than the speed of sound regularly. When the aircraft reaches close to the speed of sound what happens is quite interesting in respect of the movement of air around the wings of the plane. It is called the Prandtl-Glauert singularity and it is quite photogenic.

Conclusion to aircraft speed of sound

In two decades ranging from 1947 to 1967 there were appreciable efforts by man to reach the speed of sound and there are crafts that are unmanned and cross the speed of sound easily and that is quite a remarkable achievement. There will be further developments and we all have to wait and watch how fast air crafts will become.

Orbital Speed

The orbital speed of a celestial body measures its speed around another object’s center of gravity. This can be its speed at a given time and place in its path or may be its average speed. Depending upon the eccentricity of heavenly body's orbit the orbital speed changes as a satellite or moon gets closer to its center of gravity or further away. The two regions where speeds can change the most are pericenter and apocenter.

A satellite in orbit moves faster (pericenter) when it is close to the planet or other body that it orbits and slower (apocenter) when it is farther away. A satellite moving in a circular orbit has a constant speed which depends only on the mass of the planet and the distance between the satellite and the center of the planet.

Calculating the Orbital Speed

The speed (v) of a satellite in circular orbit is:

`v = sqrt((GM)/r)`

Where, `G` is the universal gravitational constant and the value is `6.6726 xx 10^-11 N m^2 kg^-2`,
`M`  is the mass of the combined planet-satellite system, in case Earth's mass is `5.972 xx 10^24 kg`, and we can ignore the satellite's mass, in case for smaller man made satellites.
and `r` is the radius of the orbit measured from the planet's center.
The period `P` of a satellite in circular orbit is the orbit's circumference divided by the satellite's speed:

`P = (2*pi*r)/v`

Kepler's Law for Orbital Speed:

Kepler's second law is illustrates that the line joining the Sun and planet sweeps out equal areas in equal times, this means the planet moves faster when it is nearer the Sun (perihelion). Henceforth, a planet executes elliptical motion with constantly changing angular speed as it moves about its orbit. The point of nearest distance of the planet to the Sun is known as perihelion; the point of greatest separation is known as aphelion. Therefore, by Kepler's second law, the planet moves fastest when it is near perihelion and slowest when it is near aphelion.

Arrhenius theory acid

Introduction :
According to Arrhenius an acid  is any substance that dissociates   to give  a H+ ion  in aqueous solution.

Thus an aqueous solution of hydrochloric acid will  show the presence of H+ ions and Cl- ions.
 Later it was found that the H+ ions have no free existence in water or in aqueous solution but exist in the solvated state as hydronium ion as H₃O^+.

  Thus according to Arrhenius definition of an acid,  any substance that will increase the concentration of H+ ions in water is said to be an acid.

  General Representation:  An Arrhenius acid  is generally represented by the formula with a H in the begining as HCl , H₂SO4 , HNO_3. All  acids that can donate a proton in aqueous solution or  can increase the concentration of H₃O⁺ ions in solution  are called Arrhenius acids.The dissociation of an acid in water can be represented by the equation a follows:
 If HCl be the acid then the dissociation is given as
HCl((g)  +  H₂O(l)    ---> H₃O⁺  + Cl^-

The advantage of the Arrhenius definition of an acid.

1) All protic acids that can dissociate in aqueous solution to increase the H+ ione concentration show similar properties such as :

Reaction with bases result in neutralisation of the acid and formation of water and a salt
example: HCl + NaOH----------> NaCl + H₂O
                  HNO₃ + KOH --------> KNO₃ + H₂O      

2)  The basicity of the acids depends upon number of H+ ions, an acid can releas in aqueous solution

3) The pH of any substance depends upon the number of H+ ions the substance can release in solution

Limitation of Arrhenius definition of acid>

1) Arrhenius definition of acid holds good only for acids in aqueous solution. For example
HCl (aq) ----------> H⁺(aq)  + Cl^- (aq)
      H⁺ (aq) + H₂O (l) ---------> H₃O⁺ (aq)
    But HCl in gaseous state is neither acidic nor basic.

2) Acid not dissolved in (aq) solution cannot dissociate into H+ ions. For example
     HNO3 (l) + 2H2SO4 (l) -----------> NO⁺⁺ (l) + H₃O⁺ (l) + 2HSO₄^-   (l)
Here HNO3 acts as a base

3) Arrhenius definition of acid cannot account for the acidic character of AlCl₃

Learn definition of sec

Introduction :
Learn definition of Sec is defined as the function which is used to calculate the ratio of sides of the triangle. It is also known as inverse of cos function. Sec is a one kind of trigonometric functions. Sec of an angle is the ratio of hypotenuse and the length of the adjacent side. In other words, the learn definition of Sec is the reciprocal of cos.

In a right angle triangle,

                  Sec(A)=hypotenuse       
                              adjacent side        
               Here A is a angle, Sec (A) = 1/ (cos A)        

Learn definition of sec:

Learn properties of sec angle:
Learn definition of sect is intervallic and repeats itself every 2 radians. An essential property is sec(0)=1. Few other main properties are

By the definition of sec,
           sec x               = 1/cos x
           sec( x + 2 )   = sec (x) sec ( /2)    = ∞ (infinity)
           sec(-x)            = sec(x)
           sec(x)             = i sec h(ix)

Learn important calculus relations of sec:
             d/dx sec(x) = sec(x) tan(x)    (differentiation)
            ∫ sec(x) dx   = ln sec(x) + tan(x) = ln ( /4 + /2)  (integral)

Learn series expansion of the function of sec:
           sec(x)  = 1 + x²/2 + 5x⁴/24 + 61z⁶/ 720 + ..... + (-1)ⁿ E_2n/(2n)! X_2n + ......
Here the E's are the Euler numbers of secant.

Learn domain of sec:
          Every numbers are real except /2 + k , k is an integer.

Learn range of sec:
           (-∞ , -1] U [1 , +∞)

Learn Period of sec:
                 2 π

Learn y intercepts of sec:
           y = 1

Learn of sec symmetry:
           sec(-x) = sec (x).   Because sec (x) is an even function and graph is symmetric.

Learn of sec intervals of increase/decrease:
From 0 to 2, sec (x) is increasing on (0 to /2) U ( /2  to  ) and decreasing on ( to 3 /2) U (3 /2 to 2 ).

Learn vertical asymptotes of sec:
           Vertical asymptote = /2 + k π , where k is an integer.

Learn co function for sec : 
           sec x  = cosec (90^o - x).

Practice problem for learn definition of sec:

Practice problems using learn of secant function:
1. Find the function value of sec 45^o.

Solution:
         Use the Sec's co task identity to solve the problem.
By the definition of sec,
        function for sec is  sec x   = cosec (90^o - x)
                                         sec 30^o= cosec (90^o – 30^o )
                                                      = cosec (60^o)
                                          sec 30^o = 0.866
         The solution of sec of 30^o is 0.866.

2. Find the angle of a right triangle where hypotenuse = 2, length of the adjacent side = 1 using secant function?

  Given:
         In a right angle triangle length of the hypotenuse = 2, length of the adjacent side = 1

  Solution:         
By the definition of sec,
           Sec x  =  hypotenuse/adjacent side
                      = 2 / 1
                   x = sec^-1 (2)
                   x = 60^o 
The secant angle of triangle is 60 degrees.

Electricity sources

Introduction :

Electricity is the main branch of physics, which deals with the motion of the charges. The device which produce electricity or which can convert one form of energy into another form is called the sources of electricity.The sources of elecricity can be had from nuclear plant,  fossil fuels like coal, natural gas etc. Even the solar radiation can be used to obtain electricity.Here we discuss the sources of electricity.

About Electricity sources

Electricity is the very important form of energy, which we use, in our daily life. Now these days we even do not imagine the life in the absence of electricity. The sources of electricity are cells, which are very common and very convenient in use. There are two types of the cells one are called the primary cells and t0he other are called the secondary cells. The primary cells are those, which cannot be recharged, and the secondary cells are recharged several times up to some limit. Voltaic cell is the most important type of the source of electricity.

It is the simplest form of the electrochemical cell. It consists of a glass vessel containing dil. sulphuric acid. Copper and the zinc rod are dipped in the dil. Sulphuric acid. These copper and zinc rods are called the electrodes. When the bulb of a torch is connected across the electrodes through a conducting wire, it glows that means the electricity is produced due to some chemical reaction. When sulphuric acid dissolved in water, it decomposes into ions as shown in the reaction given below

H2SO4       `->`         2H+ + SO4 2-

Zinc atoms from zinc plate begin to dissolve slowly in H2SO4 in form of Zn2+. Each zinc atom dissolved in H2SO4 from the Zn plates leaves two electrons on the Zn plate. This zinc plate becomes negatively charged.

Zn (in solution)        `->`        Zn 2+   + 2e- (on Zn plate)

The potential acquired by the Zn plate is – 0.62 Volt. When Zn ions enter the solution from the Zn plate, an equal number of H+ leaves the solution and deposit on the copper plate. The hydrogen ions get electrons from the copper plate to become neutral hydrogen atoms.

H+ + e -    `->`            H

A pair of hydrogen atom combines to form the hydrogen molecule and the bubbles of the hydrogen gas are formed. Copper plate becomes positively charged and the potential is 0.46 Volt. So the potential difference of the voltaic cell is 0.46 – (-0.62) = 1.08 Volts.

Conclusion of the electricity sources

Thus, we observed that the same potential difference is developed across the plates of the cell. That means there are some free charges, which are in motion. As we connect a resistance in the path of the free charges, it will move and the electricity is produced so that the current flows through the bulb and it will glow.

How does electricity works

Introduction:

The basic electrical circuits consists of the following ;

The Source which generates power such as a generator,

the load which utilizes the power,

and two wires to carry the electrons act as conductor from the power source and back to power source.This is how the electricity will works.

                                        how does electricity works

Measure of electricity or power is Watts and Kilowatts.

Watts = (Volts X Amps).

Electron: In order to understand electrons, we need to have a understanding of the atom. Atom consists of  a nucleus(having protons and neutrons)  and electrons revolving around it in circular orbits.

How does electricity works

Current: Movement of charge carriers (electrons) from one place to another place is called as current.

One amp is defined as one coulomb of charge carriers passed through a cross section of conductor per unit time.That is  6.28 x 10^18 electrons per second.

Voltage: It is the electrical force that gives the energy to free electrons to move from one atom to another. Just as water needs some pressure to force it through a pipe, electrical current needs some force to make electron flow. "Volts" is the unit of measurement of "electrical pressure" that causes current flow. Voltage is also called as potential difference between two points along a conductor.

Load: Load is the one which consumes the generated energy

 The power source generates the voltage which force the electrons to flow through the conductors when load is connected and it is a closed loop. The load utilizes the power to convert electrical energy to some other form.

Importance of electricity:

Electricity is  life blood that flows in our society. Our survival based on electricity. Electricity generates in several forms. Electricity most basic generated form is lightning. Portable devices like torches,mobiles use batteries which is a form of static electricity.Sun is also one of the major source of electricity if we convert the radiated light energy to electricity with the help of photocells.

The very fundamentals of electricity starts with electrons. Electron flow depends upon the type of material . Some materials do not allow electrons to move through it freely from one atom to another, those type of materials called as Insulators. Some materials allow free flow of electrons those are good conductors of electricity called as conductors. The movement of electrons referred as current.

Electrons can freely move in conductors then why we need voltage ?

 Conductors having the movement of electrons in a random direction in order to make the the electrons to flow in a particular direction we need to impart energy for the electrons that energy is called as Voltage. We can compare this two terms with a dam having potential head as voltage and the stream of water flow can be compared with electron flow. The more the potential head in the dam the larger will be the flow of water.

A battery works in the similar way it is having two terminals, a positive terminal and a negative terminal. The source, whether may be generator or battery, will push the electrons to the negative terminus. The rate at which it pushes the electrons is the voltage. The equipment, electronics appliances you that will consume electricity  is called the load. The electrons will leave the negative side of the power source, energize the equipment, and flow to the positive side of the power source.

Resistance: It is the force that resists the flow of electrons.. The units of resistance Ohms..

OHM’S LAW:Ohm’s law  state that voltage  (V) in a circuit is directly proportional to the , current or amps are (I) .

 V=IR.

In  a light bulb. The thin wire inside  the bulb is called filament. When power is applied to the bulb, the tungsten filament resists the flow of electrons. We can calculate that resistance by Making Resistance as subject of formula, r=V/I. So a 60 Watt light bulb’s resistance would be 240 Ohms.

There are basically two types of electrical currents,
    Direct current (DC)

   Alternating current (AC).

Direct current :Here the magnitude of the current is constant through out the wave form .Example battery  produces the DC current that flows in one direction only that is moving directly from the negative terminal to the positive terminal of the battery.

Alternating current: The magnitude of the current continuously varies with time.Example of AC power sources Generator.The magnitude is varying with time so frequency comes into picture. Frequency can be defined as the number of cycles produced in a given unit of time.This is called Hertz (Hz) or Cycle.

How does electricity works

Advantages:

The advantage of alternating current is that from  power  generating stations send millions of volts from their power plants through small conductors to transformers that will step down to required voltages in the distribution end.

Fcc unit cell

Introduction to unit cell
A regular three dimensional arrangement of points in space is called a crystal lattice. A unit cell is the smallest of a crystal lattice which, when repeated in different directions generates the entire lattice

Face centered cubic unit cell

A face centered cubic unit cell contains atoms at all the corners and at the centre of all the faces of the cube. Each atom located at the face centre is shared between two adjacent unit cells and only half of each atom belongs to a unit cell. Thus, in a face centered cubic unit cell:

1. 8 corners atoms × 1/8 atoms per unit cell=1 atom
2. 6 face centered atoms × 1/2 atoms per cell=3 atoms

Therefore, total no. of atoms per unit cell = 4 atoms

Packing efficiency of fcc unit cell

Packing efficiency is the percentage of total space filled by the particles. Let us calculate the packing efficiency of fcc unit cell. Let the unit cell edge be ‘a’  and face diagonal be ‘b’.
We know that b=√2a
If r is the radius of the sphere, we find
    b = 4r =√2a or a = 2√2r
we know that each unit cell in fcc structure, has effectively 4 spheres. Total volume of four spheres is equal to 4×(4/3)πr³ and the volume of the cube is a³ or (2√2r)³.
Therefore,
Packing efficiency of fcc unit cell
=volume of 4 spheres ×100/volume of unit cell  %
=4×(4/3)πr³×100/(2√2r)³
=74%

Density of unit cell

Volume of unit cell = a³
Mass of the unit cell =number of atoms in unit cell×mass of each atom
=z × m
Where z is the number of atoms in unit cell and m is the mass of single atom.
Mass of an atom present in a unit cell:
    m = M/N_a   (M is molar mass)
therefore, density of the unit cell =mass/volume
         =z×m/a³ = z×M/a³×N_a
     d   =    zM/a³N_a

Summay

The number of atoms in a fcc unit cell is four and these are present at all corners as well as at the centre of all faces of the cube

Make a fuel cell

Introduction :
A Fuel Cell is a device that converts the energy of the chemical reaction between a fuel and an oxidant into electricity and heat.  It is easy to make a fuel cell working, by using an anode, cathode, catalysts and most often an electrolyte.  Fuels and oxidants are also necessary to make a fuel cell.  Fuel cells are combined into groups to obtain a usable voltage and power output, called stacks. Fuel cells generate electricity electrochemically, rather than mechanically, so they are more efficient over a wider load factor and can cut greenhouse gases by over 50 percent.  Fuel cells are very much different from batteries. Fuel cells consume reactant from an external source, which must be replenished.  Fuel cells produce electricity with an efficiency of about 70 % compared to thermal plants whose efficiency is about 40%.

How to make a fuel cell

We can make a fuel cell (Hydrogen Fuel Cell) in our kitchen in just 10 minutes, and demonstrate how hydrogen and oxygen combines to give clean electricity.
To make a fuel cell, we would need:

• One foot of platinum coated nickel wire along with small piece of wood or Popsicle stick.  
• A 9 volt battery clip and a 9 Volt battery.
• A little transparent sticky tape.
• One glass full of water.
• Volt meter device.

Hydrogen-oxygen Fuel cell

One of the most successful fuel cells uses the reaction of hydrogen as fuel and oxygen as oxidant to form water (Hydrogen oxygen fuel cell).  The cell was used for providing electrical power in the Apollo space programme.  The water vapors produced during the reaction were condensed and added to the drinking water supply for the astronauts.  In the cell, hydrogen and oxygen are bubbled through porous carbon electrodes into concentrated aqueous solutions of sodium hydroxide.  Catalysts like finely divided platinum or palladium metal are incorporated into the electrodes for increasing the rate of electrode reactions.

Catalysis plays a very important role in Hydrogen oxygen fuel cells, separating the electrons and protons of the reactant fuel (at the anode), and forcing the electrons to travel though a circuit, generating electrical power.  At the cathode, another catalytic process takes the electrons back, combining them with the protons, which have traveled across the electrolyte and the oxidant to form waste products like carbon dioxide and water.
The electrode reactions of Hydrogen oxygen fuel cell are given below:
Cathode reaction:     O₂ (g) + 2H₂O (l) + 4e⁺    4OH^–(aq)
Anode reactions:       2H₂ (g) + 4OH^–(aq)  4H₂O (l) + 4e^–
Overall reactions:     2H₂ (g) + O₂ (g)   2 H₂O (l)
The cell can run continuously as long as the reactants are supplied.

Alcohol fuel cell

Introduction

A fuel cell is an electrochemical device which converts the chemical energy of compounds into electrical energy via electrochemical reactions. Unlike a conventional battery, a fuel cell is not an energy-storing apparatus but reactants are continuously replenished into the cell separately during the operation. A Hydrogen rich compound or pure hydrogen is used as a fuel, while oxygen from the air or pure oxygen commonly serves as oxidant. The benefits obtained using a fuel cell for energy production are high efficiency and low emissions of harmfull effluents.

Alcohol fuel cell

In an alcohol fuel cell, as the name indicates alcohol is used as a fuel to produce electricity.  The cell in which Methanol is directly used as fuel is named as Direct Methanol Fuel cell. The technology behind Direct Methanol Fuel Cells (DMFC), a particular example for alcohol fuel cell.  It is still in the early stages of development, but it has been successfully demonstrated powering mobile phones and laptop computers—potential target end uses in future years.

In the early 1990s, DMFCs were not appreciated because of their low efficiency and power density, as well as other problems. Improvements in catalysts and other recent developments have increased power density to 20-fold and it is expected that the efficiency may eventually reach 40%.

DMFC is very similar to the PEMFC in that the electrolyte is a polymer and the charge carrier is the hydrogen ion (proton). However, in a DMFC, the liquid methanol (CH₃OH) is oxidized in the presence of water at the anode generating CO₂, hydrogen ions and the electrons that travel through the external circuit as the electric output of the fuel cell. The hydrogen ions travel through the electrolyte and react with oxygen from the air or pure oxygen, used as oxidant and the electrons from the external circuit to form water at the anode completing the circuit.

Cell reactions

Reaction at the Anode:      CH₃OH + H₂O => CO₂ + 6H+ + 6e^-
Reaction at the Cathode:   3/2 O₂ + 6 H⁺ + 6e^- => 3 H₂O
Overall Cell Reaction:       CH₃OH + 3/2 O₂ => CO₂ + 2 H₂O

These cells have been tested to work in a temperature range from about 50ºC-120ºC. This low operating temperature and advantage of no requirement for a fuel reformer make the DMFC an excellent candidate for very small to mid-sized applications, such as cellular phones and other consumer products, up to automobile power plants.

One of the drawbacks of this alcohol fuel cell is that the low-temperature oxidation of methanol to hydrogen ions and carbon dioxide requires a more active catalyst, which typically means a larger quantity of expensive platinum catalyst is required than in conventional PEMFCs.

One other demerit of driving the development of alcohol fuel cells is the fact that methanol is toxic. Therefore, some companies have been developing the advantageous Direct Ethanol Fuel Cell (DEFC). The performance of the DEFC is currently only about half that of the DMFC, but this gap is expected to narrow within very short time.

Diagram of atom structure

Introduction :
Atom is defined as the very small particle. The atoms are having many chemical properties of the elements. The atoms structure are having the nucleus at its center. The electrons are also present in the atom. The electron is always surrounds the nucleus part. The particles like protons and neutrons are also present in the atom.

Various particles present in the diagram of an atom structure

The atom diagram structure consists of three types of particles. They are defined below the following,
1. Protons
2. Neutrons
3. Electrons

Explanation for the various particles for the diagram of atom structure

The diagram of Structure of an Atom is shown below,
                 

Protons:
The protons present in the atom are having a positive charge. The positive charge is equal to the negative charge present in the electrons. The number of particles present in the atoms is used for the representation of the atomic number. Protons are 1836 times greater than the electrons. The proton structure is discovered by the scientist named Ernest Rutherford.

• The mass of the proton is given by 938 MeV/c² = 1.67 x 10^-27 kg.
• The charge of the3 proton is given by 1.602 x 10^-19 Coulombs.
• The diameter of the proton is given by 1.65 x 10^-15 m.

Electron:
The electrons are having the negative charges. The electrons cannot able to split into the further particles. The electrons move freely in the diagram of an atom. The electron forms the electron clouds.

• The mass of an electron present in the atom is given by 9.2095 x 10^-31 kg.
• The charge of an electron present in the atom is given by -1.602177 x 10^-19 C.
• The electron rest energy present in the atom is given by 0.511 MeV.
• The spin of an electron present in the atom is given by + `(1)/(2)` or -`(1)/(2)`

Neutron:
The charge of the neutron present in the atom is having neutral charge. The neutrons present in the atom are used to represent the isotope of the element.

• The mass of the neutron is given by 1.67492729 × 10⁻²⁷ kg.
• The charge of the neutron is given by 0.  
• The spin of the neutron is given by `(1)/(2)`