Infinity Science study: Networking, LAN, WAN, MAN, Topology, PSTN, VAN, ISDN, Extranet, Firewall.

NETWORKING

Computer networking relates to the communication between a group of two or more computer systems linked together.

The network of computer can be classified as

LOCAL AREA NETWORK (LAN):

It is a system in which computer can be inter-connected within a geographical spread over 1km. All the terminals are connected to the main computer called server.

WIDE AREA NETWORK (WAN):

In a WAN the connected computer are much far from each other and are connected by telephone lines or radio webs. Such network may spread across countries.

METROPOLITAN AREA NETWORK (MAN):

It is data network design for a town or a city. It is main purpose to share hardware and software resource among the various users e.g., a cable TV network.

NETWORK RELATED TERMS

TOPOLOGY:

A network topology in physical layout of the computers, cables other peripherals on network. E.g., Bus Topology, Tree Topology Mesh Topology, Ring Topology.

NETWORK INTERFACE CARD (NIC):

It is also called network adopter. It is hardware component that connect a computer to a computer network.

INTERNET:

It is a public or global network that connects computer systems across the world called internet.

INTRANET:

It is Private utilizing internet type tools, but available only within that organization.

EXTRANET:

It is an internet that can be partially accessed by authorized outside users, enabling to exchange information over the internet in a secure way called extranet.

PUBLIC SWITCH TELEPHONE NETWORK (PSTN):

It is a design for telephone, which required modem for data communication.

VALUE ADDED NETWORK (VAN):

It provides electronic data interchange (EID) facility. It subscribe like invoices, sale-purchase order.

INTEGRATED SERVICE DIGITAL NETWORK (ISDN):

It is used voice, video and data services It uses data transmission and it combined both circuit and packet switching.

FIREWALL:

It is combination of software and hardware based device permit or deny networks transmission based on a set of rules and is frequently used to protect network from unauthorized access while permitting legitimate communication to pass.

REPEATER:

It is used on a network to regenerate signals to be sent over long distance.

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Infinity Science study: Physical Quantities !!! Definition and Unit !!! Scalar, Vector, Displacement, Velocity and Acceleration.

PHYSICAL QUANTITIES

SCALAR QUANTITIES:

• Physical quantity which have magnitude only and no direction are called Scalar Quantities.

          Example:- Mass, Speed, Volume, Work, Time, Power, Energy etc.

VECTOR QUANTITIES:

• Physical quantity which have magnitude and direction both and witch obey the triangle law are called vector quantities.

          Example:- Displacement, Acceleration, Velocity, Force, Momentum, Torque etc.

KINEMATICS

• It is branch of mechanics, which deals with the motion of object.

DISTANCE:

• The length of the actual path covered by a body in a particular time interval is called distance. It always positive.
• It is a scalar quantity which has magnitude only. Its unit is also Metre.

DISPLACEMENT:

• The difference between the final and the initial position of an object is called Displacement. It may be positive, negative or zero.
• It is a Vector quantity. Its unit is Metre.
• The magnitude of displacement may or may not be equal to the path length travelled by an object.                                                                                                                                                                                              Displacement ≤ Distance

SPEED:

• Speed is the distance covered by a moving body in unit time. Its unit is m/s.
• It is a Scalar quantity. It is always equal to or greater than magnitude of the velocity.
• The average speed of a particle for a given interval of time is defined as the ratio of total distance travelled to the total time taken.

                        Average Speed = Total distance travelled / Total time taken

• If a body covers first half distance with speed v₁ and the next half with the speed v₂ then

                                   Average Speed = 2v₁v₂ / v₁+v₂

VELOCITY:

• The rate of change of Displacement of a body is called velocity. Its unit is Metre/Second (m/s).

                                             Velocity = Displacement / Time

• Velocity is Scalar quantity. It may be positive or Negative.

                                    Average velocity = Total displacement / Total time

• If a body covers first half distance with velocity v₁ and the next half with the velocity v₂ then

                                   Average Velocity = 2v₁v₂ / v₁+v₂

• If a body travels with uniform velocity v₁ for time t₁ and with the uniform velocity v₂ for time t₂, then

                                 Average Velocity = v₁t₁ + v₂t₂ / t₁ + t₂

• If a body is moving on a circular path, then after completing one complete cycle, its average velocity of is zero.

UNIFORM VELOCITY:

• An object is said to be moving with uniform velocity if it undergoes equal displacements in equal time intervals of time.

NON-UNIFORM VELOCITY:

• An object is said to be moving with non-uniform velocity if it undergoes unequal displacements in equal time intervals of time.

RELATIVE VELOCITY:

• When two bodies are moving in the straight line, the speed (or velocity) of one with respect to  another is known as its  relative speed (or velocity).

ACCELERATION:

• It is the rate of change of velocity. Its unit is Metre / Second Square (m/s²). It is a Vector quantity.
• When the velocity of a body increases with time then its acceleration is positive and if velocity decreases with time then its acceleration is negative and it’s called Retardation or Deacceleration.
• Acceleration of an object is zero. If it is at rest or moving with the uniform velocity.

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Infinity Science study: What is Rainbow,Primary Rainbow, Secondary Rainbow.

WHAT IS RAINBOW?? STATE CONDITIONS FOR OBSERVING RAINBOW.

Rainbow is the beautiful illustration of dispersion of light and is observed during the rainfall or after rainfall or when we look at a water fountain provided the sun is shining at back of the observer (Condition for observing Rainbow).

Rainbow is formed due to the dispersion of light, refraction and total internal reflection of light in the droplets present in the atmosphere. Thus, Rainbow is combined effect of refraction, total internal reflection and dispersion of light.

Sometime two rainbows are seen. The inner rainbow is called Primary Rainbow and the outer one is called Secondary Rainbow.

PRIMARY RAINBOW:

When sun light fall on a water drop suspended in air, then part of light is reflected and part of light is refracted. The refracted light is dispersed (or splits) into its constituent colours. Thus, the water drop suspended in air act as glass prism. The red colour is deviate least and the violet colour is deviated the most. Different colours of refracted sunlight fall on opposite side of the drop. Now each colour suffers total internal reflection. The reflected colour on reaching the lower surface of water drop suffers another refraction. The refracted colours gives rise to spectrum called Primary Rainbow. 

Thus primary Rainbow is formed due to two refractions, one total internal reflection and another is dispersion is light by the droplets (tiny water drop) suspended in the air. The outer edge of the primary  Rainbow is red and the inner edge is violet.

An observer can see the red colour of the Rainbow if the angle between the beam of the sunlight and the light coming outer of the drop is 42 degree. However, the observer sees the violet colour of the rainbow when angle between the beam of sun light and light coming outer of the drop is 40 degree.

SECONDARY RAINBOW:

It is formed due to refractions, two internal reflection and dispersion of light by the droplets suspended in air.

Secondary rainbow is coloured band having violet colour on outer side and red colour on the inner side.

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Infinity Science study: Why +ve & -ve Attract, Conductor, Semiconductor and Insulator.

• WHY DOSE A POSITIVE CHARGE ATTRACT A NEGATIVE CHARGE ?

     Ans:It is a tendency of everybody have minimum electric potential i.e., to obtain zero potential. A positive charge means deficit of electrons while the negative charge indicates excess of electrons. Consequently, positive and negative charges attract each other to have minimum eclectic potential.

ELECTRICAL MATERIALS

The materials used in electricity and electronics can be broadly divided into three major types.

• Conductor
• Semiconductor
• Insulator

Conductor (e.g copper, aluminum etc.) conduct current very easily while insulators (e.g glass, mica, paper) practically conduct no current. In other words, conductors have small resistivity and insulator have high value of resistivity. The resistivity of semiconductors (e.g. germanium, silicon etc.) lies between conductors and insulators.

CONDUCTOR

1. Conductors are formed by metallic bonds. These bonds are based on structure positive metals ions surrounded by a clouded of electron.
2. Conductors have positive temperature coefficient of resistance i.e their resistance increases with rise the temperature and vice- versa as mention in figure.
3. Conductors are use to Carry current in the electric circuits.

SEMICONDUCTOR

1. Semiconductors are formed by covalent bonds.
2. Semiconductors have negative temperature coefficient of resistance i.e. their resistance decreases with the rise in temperature and vice versa as mention in figure.
3. Semiconductors are used in manufacturing of electronics devices (e.g crystal diodes, transistor etc.)

INSULATOR

1. Insulators are predominantly covalent compounds. The valances electrons are tightly locked with neighboring atoms are not available to support flow the current.
2. Insulators have negative temperature coefficient of resistance i.e. their resistance decreases with rise of temperature and vice- versa.
3. Insulators are used to confine the current to desired path.

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Infinity Science study:Concept of E.M.F & P.D, Ohm's law, Resistance, Conductance & Conductivity

Concept of E.M.F. and Potential Difference

There is a distinct between e.m.f. and potential difference. The e.m.f. of a device, says a battery, is measure of energy the battery gives to each coulomb of charge. Thus if a battery supplies 4 joules of energy per coulomb, we say that it has an e.m.f. of 4volt. This energy given to each coulomb in a battery is due to the chemical action.

 The potential difference between to points, say A and B, is a measure of the energy use by one coulomb in moving from A to B. Thus if the potential difference between points A and B is 2 volts, it means that each coulomb will give up an energy of 2 joules in moving from A to B.

Ohm’s Law:

The relationship between voltage across and current through a conductor was first discovered by German scientist George Simons Ohm. This relationship called Ohm’s law and may be stated as:

 The current (I) flowing through conductor is directly proportional to the potential difference (V) across its ends provided physical conditions (Temperature, Strain, etc.) do not change i.e.,

I ∞ v

                   Or                                           V/I = R = (Constant)

Where R is constant of proportionality and is called resistance of the conductor. For example, If in figure (1) the potential difference between point A and B of the conductor is V and the current flowing is I, then V/I will be constant and equal to R, resistance of the conductor between points A and B. If V is double up , current will also be double up so that ratio V/I is constant.

If a *graph is drawn between applied potential difference (V) and current (I) flowing through the conductor, it will be straight line passing through the origin as shown in figure (2). Note slop of the graph gives the resistance of                                                  the conductor (tanϴ = V/I = R).

Resistance:

The resistance of a conductor is define as the ratio of potential difference applied across its ends to the resulting current through the conductor i.e.,

                                                              

                                                          R =V/I                                                                                                                                                                                                                   Resistance is an opposition to the flow of current. If the resistance of the circuit is doubled, the current is reduced to one half. If the resistance tripled, the current is reduced to one third and so on. The SI unit of potential difference is V or 1V and that of current is 1A. Therefore SI Unit of resistance is V/I which has been given a special name ohm (symbol Ω).

1 ohm = 1Ω = 1 V/A

A conductor is said to have a resistance of 1 ohm if a potential difference of 1V across its ends causes a current of 1A to flow through it.

Calculating Resistance:

                                                           R = ρ L/A

Where ρ (Greek latter ‘Rho’) is called Resistivity or Specific Resistance of the material, Its value depend upon the nature of the material and temperature.

Resistivity or Specific Resistance:

                                                           R = ρ L/A

If L = 1m; A = 1m*m, then R= ρ

Hence, specific resistance (or resistivity) of a material is the resistance offer by 1m length of a wire material having area of cross-section of 1m*m .

Conductance:

The reciprocal of resistance of a conductor is called its conductance (G).                   

            If a conductor has a resistance R, then the conductance G is given by:

                                                            G = 1/R

SI Unit conductance is Siemens.

Conductivity:

The reciprocal of resistivity of a conductor is called its conductivity.                          

         Its denoted by the symbol σ. If a conductor has resistivity ρ, then the conductivity is given by:

                                                            σ =1/ρ

SI Unit of conductivity is Siemens per meter (S).

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Infinity Science study: Kirchhoff's Laws(KVL and KCL) and Sign Convention

Kirchhoff’s Laws:

  

Some time we encounter circuit where simplification by series and parallel combination is impossible. Consequently, Ohm’s law cannot be applied to solve such circuits. Kirchhoff gave two laws to solve such complex circuits, namely:

1.  Kirchhoff’s Current Law (KCL)    2.  Kirchhoff’s Voltage Law (KVL)

Kirchhoff’s Current Law (KCL): 

The algebraic sum of the currents meeting at a junction in an electric circuit is zero.

An algebraic sum in which the sign of the quantity is taken into account. For example, consider four conductors carrying currents I1, I2, I3 and I4 and meeting at appoint O as positive, the currents flowing away from point O will be assigned negative sign. Thus, applying Kirchhoff’s current law to the junction O in figure (1), we have,

   (I1) + (I4) + (-I2) + (-I3) = 0

                       I1 + I4 = I2 + I3

i.e.,    Sum of incoming current = sum of outgoing currents

Hence, Kirchhoff’s current law may also started as under:

The sum of current flowing towards any junction in an electrical circuit is equal to the sum currents flowing away from the junction.

Note: Kirchhoff’s current law also called junction rule.

Kirchhoff’s Voltage Law (KVL):

This laws relate to e.m.fs and voltage drops in a closed circuit or loop and may be started as under:

 In any closed electrical circuit or mesh, the all algebraic sum of all the electromotive forces (e.m.fs) And the voltage drops in resistor is equal to zero, i.e.,

In any closed circuit or mesh,

Algebraic sum all e.m.fs + Algebraic sum of voltage drops = 0

The validity of Kirchhoff’s voltage law can be easily established by referring to the loop ABCDA show in figure (2). If we start from any point (say point A) in this closed circuit and go back to the point(i.e., point A) after going round the circuit, the there is no increase or decrease in potential. This means the algebraic sum of the e.m.fs of all the sources (here only one e.m.f. source is consider) met on the way plus the algebraic sum of the voltage drops in resistances must be zero. Kirchhoff’s voltage law based on the law of *conservation of energy, i.e., net change in the energy of a charge after completing the closed path is zero.

Note: Kirchhoff’s voltage law is also called loop rule.
Sign convention:

While applying Kirchhoff’s voltage law to a close circuit, algebraic sum are considered. Therefore, it is very important to assign proper signs to e.m.fs and voltage drops in the closed circuit. The flowing sign convention may be followed:

A rise of potential should be considered positive and fall in potential should be considered negative.

Thus in figure (3a) as go from A to B (i.e., from negative terminal of the cell to the positive terminal), there is a rise in potential.

In figure (3b) as we go from A to B, there is a rise in potential.

In figure (3c) as we go from C to D, there is a fall in potential.

In figure (3d) as we from C to D, there is again a fall in potential.

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Infinity Science study:Network Theorems (Definition of Network, Active, Passive, Node,Junction, Branch,Loop and Mesh)

Network Theorems

Network :

Any arrangement of electrical energy sources, like resistance and other circuit elements is called an electrical network.

Network Terminology

• Active element:

An active element is one which supplies electrical energy to the circuit. In figure (01) E1 & E2 are the active element because they supply energy to the circuit.

• Passive element:

A passive element is one which receives electrical and then either coverts it into heat (resistance) or stores in an electric field (capacitance) or magnetic field (inductance). In figure (01), there are three passive elements, namely R1, R2, and R3. These Passive elements receive energy from the active elements (i.e., E1 & E2).

• Node:

A node of a network is an equipotential surface at which two or more circuit elements are joined. In figure (01) circuit elements R1 and E1 are joined at A and hence A is the node.

• Junction:

A junction is that point in a network where three or more circuit elements are joined. In figure (01) there are only two junction points i.e., B & D.

• Branch:

A branch is that Part of a network which Lies between two junction points. In figure (01) there are a total of three branches i.e., BAD, BCD and BD.

• Loop:

A loop is any close Path of a network. In figure (01) ABDA, BCDB and ABCDA are the loop.

• Mesh:

A mesh is most elementary form of a loop and cannot be further divided into other loops. In figure (01) both loops ABCD and BCDB qualify as meshes because they cannot be further divided into other loops. The loop ABCDA cannot be called a mesh because it encloses two loops ABDA and BCDA.

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