Internet and Its Services
The Internet has gained popularity and emerged as an important and efficient means of communication. The idea of introducing the Internet was to allow millions of people to share information and ideas, sound, video clips using their computers across the world. The Internet is a worldwide network of networked computers those are able to exchange information with each other. It consists of thousands of separately administered network of various sizes and types.
Internet
Internet stands for International Network, which began in 1950's by Vint Cerf known as the 'Father of Internet. Internet is a 'network of networks' that consists millions of private and public networks of local to global scope. Basically, network is a group of two or more computer systems linked together.
The data move around the Internet is controlled by protocols. Under TCP/IP protocol (Transmission Control Protocol/Internet Protocol), a file is broken into smaller parts by the file server called packets. All computers on the Internet, communicate with one another using TCP/IP, which is a basic protocol of the Internet.
History of Internet
In 1969, the University of California at Los Angeles, the University of Utah were connected as the beginning of the ARPANET (Advanced Research Projects Agency Network) using 50 kbits circuits. It was the world's first operational packet switching network. The goal of this project was to connect computers at different universities and U.S. defence.
In mid 80's another federal agency, the National Science Foundation, created a new high capacity network called NSFnet, which was more capable than ARPANET. The only drawback of NSFnet was that it allowed only the academic research on its network and not any kind of private business on it. So, private organisations and people started working to build their own networks, which were later interconnected with ARPANET and NSFnet to form the Internet.
Advantages of the Internet
(i) Allows you to easily communicate with other people.
(ii) Global reach enables one to connect anyone on the Internet.
(iii) Publishing documents on the Internet saves paper.
(iv) A valuable resource for companies to advertise and conduct business.
(v) Greater access to information reduces research times.
Disadvantages of the Internet
(i) It is a major source of computer viruses.
(ii)Messages sent across the Internet can be easily intercepted and are open to abuse by others.
(iii) Much of the information is not checked and may be incorrect or irrelevant.
(iv) Unsuitable and undesirable material available that sometimes are used by notorious people such as terrorists.
(v) Cyber frauds may take place involving Credit/Debit card numbers and details.
Internet Connections
Bandwidth and cost are the two factors that help you in deciding which Internet connection is to use. The speed of Internet access depends on the bandwidth.
Some of the Internet connections available for Internet access are as follows
Dial-Up Connection
A Dial-up is a method of connecting to the Internet using more...
Computer Security
Computer security is also known as cyber security or IT security. Computer security is a branch of information technology known as information security, which is intended to protect computers. It is the protection of computing systems and the data that they store or access.
Methods to Provide Protection
There are four primary methods to provide protection
System Access Control It ensures that unauthorised users do not get into the system by encouraging authorised users to be security conscious.
Data Access Control It monitors who can access what data, and for what purpose. Your system might support mandatory access controls with these. The sytem determines access rules based on the security levels of the people, the files, and the other objects in your system.
System and Security Administration It performs offline procedures that makes or breaks secure system.
System Design It takes advantage of basic hardware and software security characteristics.
Components of Computer Security
Computer security is associated with many core areas. Basic components of computer security system are
Confidentiality It ensures that data is not accessed by any unauthorised person.
Integrity It ensures that information is not altered by any unauthorised person in such a way that it is not detectable by authorised users.
Authentication It ensures that users are the persons they claim to be.
Access Control It ensures that users access only those resources that they are allowed to access.
Non-Repudiation It ensures that originators of messages cannot deny they are not sender of the message.
Availability It ensures that systems work promptly and service is not denied to authorised users.
Privacy It ensures that individual has the right to use the information and allows another to use that information.
Stenography It is an art of hiding the existance of a message. It aids confidentiality and integrity of the data.
Cryptography It is the science of writing information in a 'hidden' or 'secret' form and is an ancient art. It protects the data in transmit and also the data stored on the disk.
Some terms commonly used in cryptography are
(i) Plain Text It is the original message that is an input.
(ii) Cipher It is a bit-by-bit or character-by character transformation without regard to the meaning of the message.
(iii) Cipher Text It is the coded message or the encrypted data.
(iv) Encryption It is the process of converting plain text to cipher text, using an encryption algorithm.
(v) Decryption It is the reverse of encryption, i.e. converting cipher text to plain text.
Sources of Cyber Attack
The most potent and vulnerable threat of computer users is virus attacks. A computer virus is a small software program that spreads from one computer to another and that interferes with computer operation. It is imperative for every computer user to be aware about the software and programs that can help to protect the personal computers from attacks.
The sources of attack can more...
Metals and Non-metals: There are more than 114 elements present in the periodic table. These elements can be broadly classified into two categories i.e., metals and non-metals. Out of 114 elements, 22 are non-metals.
Physical properties of metals:
(i) They are usually shiny i.e. have a metallic luster.
(ii) Metals have a high density
(iii) Metals are ductile i.e. they can be drawn into wires.
(iv) Metals are malleable i.e. they can be founded into thin sheets.
(v) Metals are good conductors of electricity.
(vi) Metals have high melting point and are generally in solid state at room temperature.
(vii) Metals are good conductors of heat and sound.
Uses of metals:
(i) Metals are very important for modern humans it is not possible to imagine our life without them.
(ii) Metals are used in manufacturing of bridges, railways, aeroplanes, diesel mobile units (DMU), electric mobile units (EMU), motor cars, electric motors, telephones, televisions, interplanetary space vehicles, or even common articles like cooking utensils and coins.
(iii) Metals are very important for the economy of a country. Some metals, such as titanium, chromium, manganese and zirconium are strategic metals. These metals and their alloys find wide applications in atomic energy, space science projects, jet engines and high grade steels.
(iv) Gold and silver ornaments are obtained from small pieces of metals by hammering.
Noble metal: Noble metals are metals that are resistant to corrosion or oxidation, unlike most base metals. Examples include tantalum, gold, platinum, and rhodium.
Precious metal: A precious metal is a rare metallic chemical element of high economic value precious metals include the platinum group metals: ruthenium, rhodium, palladium, osmium, indium, and platinum, of which platinum is the most widely traded.
Alloy: An alloy is a mixture of two or more elements in solid solution in which the major component is a metal. Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modify the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster. Examples of alloys are steel (iron and carbon), brass (copper and zinc), bronze (copper and tin), and duralumin (aluminium and copper).
Alloy
Composition
Uses
1. Brass
Cu = 80%, Zn = 20%
For making utensils and cartridges.
2. Bronze
Cu = 90%, Sn = 10%
For making statues, medals, ships, coins and machines
3. Solder
Sn = 50%, Pb = 50%
For joining metals, solding wire and electronic components etc.
Introduction
The term acid, in fact, comes from the Latin term acere, which means “Sour”. In everyday life we come across many compounds that chemists classify as acids. Bases are compounds which taste bitter eg. Milk of magnesia. Salts also have wide applications for example ammonium chloride is used as electrolyte in dry cells, sodium bicarbonote (baking powder) in the manufacture of glass etc.
Properties of acids and bases
A. Properties of acids
Chemical properties:
(i) Action of metals: Metals generally react with dilute acids to form their respective salt and hydrogen.
\[Metal+Acid\to Salt+Hydrogen\]
(ii) Action with metal oxides (Basic oxides) Metal oxides are generally basic oxides. These oxides get neutralised when they react with acids. These reactions are mostly carried upon heating e.g.
\[Basicoxide+Acid\to Salt+Water\]
\[\left( Neutralization\text{ }reaction \right)\]
(iii) Action with metal carbonates and metal hydrogen carbonates Acids react with carbonates and hydrogen carbonates to form their respective salts, water and carbon dioxide gas.
\[Carbonate/bicarbonate+Acid\to Salt+water+carbon\,\,dioxide.\]
B. Properties of bases
Chemical Properties:
(i) Reaction of metals with bases: Metals (e.g. Zn, Al, Sn) dissolve in NaOH (an alkali) to liberate hydrogen gas.
\[Zn+2NaOH\to N{{a}_{2}}Zn{{O}_{2}}+{{H}_{2}}\]
\[Sod.Zincate\]
(ii) Action with acids: Bases combine with acids to form salt and water only. It is a neutralisation reaction.
\[Base+Acid\to Salt+Water\] Non - metallic oxides react in the same way hence non- metallic oxides are acidic in nature.
Strength of Acids and Bases
The strength of an acid or a base can be easily estimated by making use of universal indicator which is a mixture of several indicators. The universal indicator show different colours at different concentrations of hydrogen ions in solution.
pH Scale
pH Scale: It is a scale that is used for measuring \[{{H}^{+}}\] ion (Hydrogen ion) concentration of a solution. The term pH stands for "potential" of "hydrogen". It is the amount of hydrogen ions in a particular solution.
For acids pH< 7
For bases pH > 7
For neutral substances pH = 7
Importance of pH in Daily Life
(i) Blood pH: For proper functioning our body needs to maintain blood pH between 7.35 and 7.45. Values of blood pH greater than 7.8 or less than 6.8 often results in death.
(ii) Acid rain: When pH of rain water is less than 5.6, it is called acid rain, when acid rain flows into rivers, it lowers the pH of river water.
(iii) pH in our digestive system: We know that hydrochloric acid (HC1) produced in our stomach helps in digestion of food without harming stomach. However excess of acid causes indigestion and leads to pain as well as irritation. To get rid of this people use bases called "antacids".
(iv) pH of the soil: For their healthy growth plants require a specific pH. Soils with high peat content or iron more...
Classification of Elements and Periodicity in Properties
Classification means identifying similar species and grouping them together.
Lavoisier divided elements into two main types known as metals and non-metals.
Doberiner's Law of triads:
According to this law, "in certain triads (group of three elements) the atomic mass of the central element was the arithmetic mean of the atomic masses of the other two elements.” But in some triads all the three elements possessed nearly the same atomic masses, therefore the law was rejected. e.g., atomic masses of Li, Na and K are respectively 7, 23 and 39, thus the mean of atomic masses of 1st and 3rd element is = 7 + 39 = 23
Limitations of Doberiner's Triads: He could identify only a few such triads and so the law could not gain importance. In the triad of Fe, Co, Ni, all the three elements have a nearly equal atomic mass and thus does not follow the above law.
Newland’s Law of octaves:
According to this law "the elements are arranged in such a way that the eighth element starting from a given one has properties which are a repetition of those of the first if arranged in order of increasing atomic weight like the eight note of musical scale.)
Drawback of Newland’s law of octaves:
(i) According to Newland only 56 elements exists in nature and no more elements would be discovered in the future. But later on several new element were discovered whose properties did not fit into law of octaves.
(ii) In order to fit new elements into his table Newland adjust two elements in the same column, but put some unlike elements under the same column. Thus, Newland's classification was not accepted.
Mendeleev’s periodic table:
Mendeleev arranged 63 elements known at that time in the periodic table. According to Mendeleev "the properties of the elements are a periodic function of their atomic masses." The table consists of eight vertical column called 'groups’ and horizontal rows called 'periods'.
Merits of Mendeleev's periodic table:
(i) At some places the order of atomic weight was changed in order to justify the chemical and physical nature.
(ii) Mendeleev left some gap for new elements which were not discovered at that time.
(iii) One of the strengths of Mendeleev's periodic table was that, when inert gases were discovered they could be placed in a new group without disturbing the existing order.
Characteristics of the periodic table: Its main characteristics are:
(i) In the periodic table, the elements are arranged in vertical rows called groups and horizontal rows called periods.
(ii) There are eight groups indicated by Roman Numerals I, II, III, IV, V, VI, VII, VIII. The elements belonging to first seven groups have been divided into sub-groups designated as A and B on the basis a/similarities. The elements that are present on the left hand more...
Law of conservation of mass: This law was stated by Lavoisier in 1744. It states that "In all physical and chemical changes, the total mass of readouts is equal to total mass of products."
Law of constant proportions (or constant composition): This law was first stated by Proust in 1797. According to the law "a chemical compound is always found to be made up of the same elements combined together in the same proportions by weight" e.g. the ratio of hydrogen and oxygen in pure water is always 1: 8 by weight. This law is also called law of definite proportions.
Law of multiple proportions: This law was given by John Dalton (1803) and states that "when two elements combine to form two or more compounds, the different mass of one of the elements and the fixed mass of the one with which it combines always form a whole number ratio". This law explains the concept of formation of more than one compound by two elements.
Dalton's Atomic theory: Postulates of Dalton s Atomic Theory
(i) Matter is made up of extremely small indivisible particles called atoms.
(ii) Atoms of the same substance are identical in all respects i.e., they possess same size, shape, mass, chemical properties etc.
(iii) Atoms of different substances are different in all respects i.e., they possess different size, shape, mass etc.
(iv) Atom is the smallest particle that takes part in a chemical reaction.
(v) Atoms of different elements may combine with each other in a fixed simple, whole number ratio to form compound atoms.
(vi) Atoms can neither be created nor destroyed i.e., atoms are indestructible.
Atom: It is the smallest particle of an element which can take part in a chemical change. It may or may not be capable of independent existence.
Symbol: The abbreviation used for lengthy names of elements are termed as their symbols. The symbol of an element is the first letter or the first and another letter of English name or Latin name of the element. While writing a symbol, the first letter is always capital and the second is always small.
Molecule: It is the smallest particle of an element or compound that is capable of independent existence and shows all the properties of that substance. [The molecules of an element is made up of only one and same type of atoms, while the molecule of a compound is made up of dissimilar atoms]
Atomicity: The number of atoms present in a molecule of an element or a compound is known as its atomicity. e.g. the atomicity of oxygen is 2 while atomicity ozone is 3.
Ion: It is an electrically charged atom or group of atom. It is formed by the loss or gain of electrons by an atom. Ions are of two types :
Cation: It is positively charged ion and is formed by the loss of electron from an atom e.g. \[{{H}^{+}},\]\[N{{a}^{+}},C{{a}^{2+}},A{{l}^{3+}}\]\[,NH_{4}^{+}\], more...
A "substance" is a kind of matter that can-not be separated into other kinds of matter by any physical process, e.g. gold, silver, iron, sodium chloride, calcium carbonate etc.
Pure substance:
Is one that is a single substance and has a uniform composition. Such a substance always have the same texture and taste, e.g. water, salt, sugar etc.
Testing the purity of a substance:
The purity of substance can easily be checked by checking its melting points in case of a solid substance or by checking its boiling points in case of a liquid substance.
Types of pure substances:
Two different types of pure substances are
(i) Element: An element is a substance which can-not be split up into two or more simpler substances by usual chemical methods of applying heat, light or electric energy, e. g. hydrogen, oxygen, sodium, chlorine etc.
(ii) Compound: A compound is a substance made up of two or more elements chemically combined in a fixed ratio by weight e.g. \[{{H}_{2}}O\] (water), \[NaCl\](sodium chloride) etc.
Mixture:
A mixture is a substance which consists of two or more elements or compounds not chemically combined together, e.g. Air is a mixture of nitrogen, oxygen, inert gases, water vapour, carbon dioxide etc.
Types of mixtures:
Mixtures are impure substances. They are of two types:
(i) Homogeneous mixture: It has a uniform composition throughout and its components can-not be distinguished visually. e.g. a well-mixed sample of vinegar.
(ii) Heterogeneous mixture: It is one that is not uniform throughout. Different samples of a heterogeneous mixture may have different composition, e.g. a mixture of salt and pepper.
Solution:
It is a homogeneous mixture of two or more substances whose composition can be varied, e.g. solution of common salt in water, solution of ammonia in water. Some other examples are lemonade, coke, pepsi etc.
Separating the components of a mixture:
Various methods are used for separating the constituents of a mixture.
Depending upon the type of mixture (i.e. whether it is a homogeneous mixture or heterogeneous mixture) different methods used are given below:
Mixture
Separation Method
1.
Insoluble solid in solvent
Sedimentation followed by filtration. In case of a fine solid centrifugation is used instead of filtration
On the basis of electrical conductivity\[(\sigma )\]or resistivity \[(\rho =1/\sigma )\] the solids are classified as
(i) Metals - have low resistivity
\[\rho \tilde{\ }{{10}^{-2}}\,to\,{{10}^{-8}}\Omega m\],
\[\sigma \tilde{\ }{{10}^{2}}\,to\,{{10}^{8}}S{{m}^{-1}}\]
(ii) Semiconductors - have intermediate resistivity
\[\rho \tilde{\ }{{10}^{5}}\,to\,{{10}^{0}}\Omega {{m}^{{}}}\]
\[\sigma \tilde{\ }{{10}^{-5}}\,to\,{{10}^{0}}S{{m}^{-1}}\]
(iii) Insulators - have high resistivity
\[\rho \tilde{\ }{{10}^{8}}\Omega {{m}^{{}}}\]
\[\sigma \tilde{\ }{{10}^{-8}}S{{m}^{-1}}\]
i.e. the Semiconductors are the materials whose conductivity is more than insulators but less than conductors.
Types of Semiconductors
Intrinsic semiconductors or pure semiconductors in semiconductors forbidden energy gap Eg is more than metals or conductors and less than insulators. Silicon (Si) and Germanium (Ge) are the examples of pure semi-conductors.
In pure or intrinsic semiconductor,
\[{{n}_{e}}={{n}_{h}}={{n}_{i}}\] Where\[{{n}_{e}}=no\].of electrons: \[{{n}_{h}}=no\]. Of holes and\[{{n}_{i}}=no\]. Of intrinsic carrier concentration. Impurity like pentavalent (As, Sb, P) or trivalent (In, B, Al) are added to increase conductivity.
Depending on doping type we have
(a) n- type semiconductor (b) p- type semiconductor
(a) n - type semiconductor: Si or Ge with pentavalent doping. An atom of valency +5 occupies the position of parent atom in crystal lattice. Four valence electrons form 4 covalent bonds but 5th electron is free and weakly bound to parent atom. The ionisation energy (~ 0.01 V for Ge and 0.05V for Si) is small and even at room temperature the electron jumps to conduction band. The dopant is called donor impurity (positively charged).
(b) p - type semiconductor: Si or Ge with trivalent doping means one less electron in the 4 covalent bonds, so the 4th neighbour has a vacancy or hole that can be occupied by an electron from another site. Thus a hole is available for conduction. The trivalent atom is negatively charged as it acquires an electron and is called acceptor atom or impurity.
Formation of p - n junction: Part of p-type can be converted into n - type by adding pentavalent impurity. There is concentration gradient between p and n sides, holes diffuse from p side to n side (\[(P\to n)\]and electrons move from \[(n\to p)\]creating a layer of positive and negative charges on n and p side respectively called depletion layer. External bias is applied to cause charges to flow.
Symbol of p-n junction diode
p-n junction under forward bias: When p-side is connected to positive terminal and n - side to negative terminal of external voltage, it is said to be forward biased.
The applied voltage V is opposite to build in Potential\[{{V}_{0}}\], hence depletion layer width decreases and barrier height is reduced to\[({{V}_{0}}-V)\]. There is minority carrier injection, hence charges begin to flow. Current is in the order of mA.
(c) p-n junction under reverse bias: When p-side of p-n junction is connected to -ve terminal more...
Magnetism
Magnetism: The phenomenon of attracting magnetic substances like iron, cobalt, nickel etc. is called magnetism. A body possessing the property of magnetism is called magnet. Lodestone or magnetite is natural magnet. Earth is also a natural magnet. In magnetized substance all the atomic magnets are aligned in same direction and thus resultant magnetism is non-zero.
Bar Magnet
A bar magnet consists of two equal and opposite magnetic poles separated by a small distance. Poles are not exactly at the ends. The shortest distance between two poles is called effective length (\[{{L}_{e}}\]) and is less than its geometric length (\[{{L}_{g}}\]). For bar magnet \[{{L}_{g}}=2l\]and\[{{L}_{e}}=(5/6){{L}_{g}}\]
Properties of Magnet
(i) Attractive property: When a magnet is dipped into iron fillings it is found that the concentration of iron filings, i.e., attracting power of the magnet is maximum at two points near the ends and minimum at the centre. The places where its attracting power is maximum are called poles.
(ii) Directive property: When a magnet is suspended its length becomes parallel to N-S direction. The pole pointing north is called the north-pole while the other pointing in the geographical south is called the south pole of the magnet. The line joining the two poles of a magnet is called magnetic axis and the vertical plane passing through the axis of a freely suspended or pivoted magnet is called magnetic meridian.
(iii) Poles of a magnet always exist in pairs: In a magnet the two poles are found to be equal in strength and opposite in nature. If a magnet is broken into number of pieces, each piece becomes a magnet with two equal and opposite poles. This shows that monopole do not exist.
(iv) Repulsive property: A pole of a magnet attracts the opposite pole while repels similar pole.
Demagnetisation of Magnet
A magnet gets demagnetised, i.e., loses its power of attraction if it is heated, hammered or alternating current is passed through a wire wound over it.
Permanent and Temporary Magnets (Electromagnets)
The permanent artificial magnets are made of some metals and alloys like Carbon-steel, Alnico, Platinum-cobalt, Alcomax, Ticonal etc. The permanent magnets are made of ferromagnetic substances with large coercivity and retentivity. The temporary artificial magnets like electromagnets are prepared by passing current through coil wound on soft iron core. These cannot retain its strength for a long time. These are made from soft iron, non-metal and alloy. Electromagnets are stronger than permanent magnet.
Some Applications of Electromagnets
(i) Electric motors
(ii) Doorbells
(iii) In scrapyards to separate iron from other metals
Coulomb's Law in Magnetism
If two magnetic poles of strengths \[{{m}_{1}}\] and \[{{m}_{2}}\] are kept at a distance r apart then force of attraction or repulsion between the more...
Charge is something associated with matter due to which it produces and experiences electric and magnetic effects. The study of charges at rest is called static electricity or electrostatics while the study of charges in motion is called current electricity. There are two types of electric charge:
(i) Positive charge and (ii) Negative charge. The magnitude of elementary positive or negative charge is same and is equal to. \[1.6\times {{10}^{-19}}C\] Charge is a scalar quantity its SI unit is ampere second or coulomb.
Basic Properties of Electric Charge
(1) Similar charges repel and opposite charges attract.
(2) A charged body attracts light uncharged bodies.
(3) Accelerated charge radiates energy.
Conductors and Insulators
The materials which allow electric charge (or electricity) to flow freely through them are called conductors. Metals are very good conductors of electric charge. Silver, copper and aluminium are some of tile good conductors of electricity. The materials which do not allow electric charge to flow through them are called nonconductors or insulators. For example, most plastics, rubber, non-metals (except graphite), dry wood, wax, mica, porcelain, dry air etc., are insulators.
Coulomb's Law
It states that, the electrostatic force of interaction (repulsion or attraction) between two electric charges \[{{q}_{1}}\] and \[{{q}_{2}}\]separated by a distance r, is directly proportional to the product of the charges and inversely proportional to the square of distance between them.
\[F\propto {{q}_{1}}{{q}_{2}}\] and \[F\propto 1/{{r}^{2}}\] or \[F=k\frac{{{q}_{1}}{{q}_{2}}}{{{r}^{2}}}\]
\[K=\frac{1}{4\pi {{\varepsilon }_{0}}}\]\[=9\times {{10}^{9}}\frac{N{{m}^{2}}}{cou{{l}^{2}}}\Rightarrow {{\varepsilon }_{0}}=8.85\times {{10}^{-12}}\frac{cou{{l}^{2}}}{N{{m}^{2}}}\]
Electric Field
Electric Field: The region surrounding an electric charge or a group of charges in which another charge experiences a force of attraction or repulsion is called 'electric field'. \[\overrightarrow{E}=\frac{\overrightarrow{F}}{{{q}_{0}}},\overrightarrow{E}=\underset{{{q}_{0}}\to 0}{\mathop{\lim }}\,\frac{\overrightarrow{F}}{{{q}_{0}}}\] The S.L unit of electric field intensity is N/coul or volt/metre.
Electric Lines of Force
An electric line of force is that imaginary smooth curve drawn in an electric field along which a free isolated unit positive charge moves. Two lines offeree never intersect. If they are assumed to intersect, there will be two directions of electric field at the point of intersection, which is impossible.
Electric Flux ((\[\phi \])
The total number of electric lines of force through a given area is called the electric flux.
(a) For open surface, \[{{\phi }_{0}}=\int{d\phi =\int{\overrightarrow{E}.d\overrightarrow{s}}}\]
(b) For closed surface, \[{{\phi }_{0}}=\oint{\overrightarrow{E}.d\overrightarrow{s}}\]
Gauss's Law
The total electric flux linked with a closed surface is \[\left( \frac{1}{{{\varepsilon }_{0}}} \right)\] times the charge enclosed by the closed surface (Gaussian surface), i.e. \[\oint{\overrightarrow{E}.d\overrightarrow{s}=\frac{q}{{{\varepsilon }_{0}}}}\]
Electrostatic Potential
Potential at a point can be physically interpreted as the work done by the field in displacing a unit + ve charge from some reference point to the given point.
i.e., \[V=\frac{w}{{{q}_{0}}}\]
\[V=-\int\limits_{\infty }^{r}{\overrightarrow{E}.d\overrightarrow{s}}\] i.e. \[E=-\frac{dv}{dr}\] more...
Symbol of p-n junction diode
p-n junction under forward bias: When p-side is connected to positive terminal and n - side to negative terminal of external voltage, it is said to be forward biased.
The applied voltage V is opposite to build in Potential\[{{V}_{0}}\], hence depletion layer width decreases and barrier height is reduced to\[({{V}_{0}}-V)\]. There is minority carrier injection, hence charges begin to flow. Current is in the order of mA.
(c) p-n junction under reverse bias: When p-side of p-n junction is connected to -ve terminal
i.e., \[V=\frac{w}{{{q}_{0}}}\]
\[V=-\int\limits_{\infty }^{r}{\overrightarrow{E}.d\overrightarrow{s}}\] i.e. \[E=-\frac{dv}{dr}\]
