Wednesday, 10 February 2016

HISTORY COMPUTER

History of Computers




This chapter is a brief summary of the history of Computers. It is supplemented by the two PBS documentaries video tapes "Inventing the Future" And "The Paperback Computer". The chapter highlights some of the advances to look for in the documentaries.
In particular, when viewing the movies you should look for two things:
  • The progression in hardware representation of a bit of data:
    1. Vacuum Tubes (1950s) - one bit on the size of a thumb;
    2. Transistors (1950s and 1960s) - one bit on the size of a fingernail;
    3. Integrated Circuits (1960s and 70s) - thousands of bits on the size of a hand
    4. Silicon computer chips (1970s and on) - millions of bits on the size of a finger nail.
  • The progression of the ease of use of computers:
    1. Almost impossible to use except by very patient geniuses (1950s);
    2. Programmable by highly trained people only (1960s and 1970s);
    3. Useable by just about anyone (1980s and on).
to see how computers got smaller, cheaper, and easier to use.

First Computers


Eniac:
Eniac Computer
The first substantial computer was the giant ENIAC machine by John W. Mauchly and J. Presper Eckert at the University of Pennsylvania. ENIAC (Electrical Numerical Integrator and Calculator) used a word of 10 decimal digits instead of binary ones like previous automated calculators/computers. ENIAC was also the first machine to use more than 2,000 vacuum tubes, using nearly 18,000 vacuum tubes. Storage of all those vacuum tubes and the machinery required to keep the cool took up over 167 square meters (1800 square feet) of floor space. Nonetheless, it had punched-card input and output and arithmetically had 1 multiplier, 1 divider-square rooter, and 20 adders employing decimal "ring counters," which served as adders and also as quick-access (0.0002 seconds) read-write register storage.
The executable instructions composing a program were embodied in the separate units of ENIAC, which were plugged together to form a route through the machine for the flow of computations. These connections had to be redone for each different problem, together with presetting function tables and switches. This "wire-your-own" instruction technique was inconvenient, and only with some license could ENIAC be considered programmable; it was, however, efficient in handling the particular programs for which it had been designed. ENIAC is generally acknowledged to be the first successful high-speed electronic digital computer (EDC) and was productively used from 1946 to 1955. A controversy developed in 1971, however, over the patentability of ENIAC's basic digital concepts, the claim being made that another U.S. physicist, John V. Atanasoff, had already used the same ideas in a simpler vacuum-tube device he built in the 1930s while at Iowa State College. In 1973, the court found in favor of the company using Atanasoff claim and Atanasoff received the acclaim he rightly deserved.









Progression of Hardware


In the 1950's two devices would be invented that would improve the computer field and set in motion the beginning of the computer revolution. The first of these two devices was the transistor. Invented in 1947 by William Shockley, John Bardeen, and Walter Brattain of Bell Labs, the transistor was fated to oust the days of vacuum tubes in computers, radios, and other electronics.
Vaccum Tubes
The vacuum tube, used up to this time in almost all the computers and calculating machines, had been invented by American physicist Lee De Forest in 1906. The vacuum tube, which is about the size of a human thumb, worked by using large amounts of electricity to heat a filament inside the tube until it was cherry red. One result of heating this filament up was the release of electrons into the tube, which could be controlled by other elements within the tube. De Forest's original device was a triode, which could control the flow of electrons to a positively charged plate inside the tube. A zero could then be represented by the absence of an electron current to the plate; the presence of a small but detectable current to the plate represented a one.
Transistors
Vacuum tubes were highly inefficient, required a great deal of space, and needed to be replaced often. Computers of the 1940s and 50s had 18,000 tubes in them and housing all these tubes and cooling the rooms from the heat produced by 18,000 tubes was not cheap. The transistor promised to solve all of these problems and it did so. Transistors, however, had their problems too. The main problem was that transistors, like other electronic components, needed to be soldered together. As a result, the more complex the circuits became, the more complicated and numerous the connections between the individual transistors and the likelihood of faulty wiring increased.
In 1958, this problem too was solved by Jack St. Clair Kilby of Texas Instruments. He manufactured the first integrated circuit or chip. A chip is really a collection of tiny transistors which are connected together when the transistor is manufactured. Thus, the need for soldering together large numbers of transistors was practically nullified; now only connections were needed to other electronic components. In addition to saving space, the speed of the machine was now increased since there was a diminished distance that the electrons had to follow.

Circuit BoardSilicon Chip


Mainframes to PCs


The 1960s saw large mainframe computers become much more common in large industries and with the US military and space program. IBM became the unquestioned market leader in selling these large, expensive, error-prone, and very hard to use machines.
A veritable explosion of personal computers occurred in the early 1970s, starting with Steve Jobs and Steve Wozniak exhibiting the first Apple II at the First West Coast Computer Faire in San Francisco. The Apple II boasted built-in BASIC programming language, color graphics, and a 4100 character memory for only $1298. Programs and data could be stored on an everyday audio-cassette recorder. Before the end of the fair, Wozniak and Jobs had secured 300 orders for the Apple II and from there Apple just took off.
Also introduced in 1977 was the TRS-80. This was a home computer manufactured by Tandy Radio Shack. In its second incarnation, the TRS-80 Model II, came complete with a 64,000 character memory and a disk drive to store programs and data on. At this time, only Apple and TRS had machines with disk drives. With the introduction of the disk drive, personal computer applications took off as a floppy disk was a most convenient publishing medium for distribution of software.
IBM, which up to this time had been producing mainframes and minicomputers for medium to large-sized businesses, decided that it had to get into the act and started working on the Acorn, which would later be called the IBM PC. The PC was the first computer designed for the home market which would feature modular design so that pieces could easily be added to the architecture. Most of the components, surprisingly, came from outside of IBM, since building it with IBM parts would have cost too much for the home computer market. When it was introduced, the PC came with a 16,000 character memory, keyboard from an IBM electric typewriter, and a connection for tape cassette player for $1265.
By 1984, Apple and IBM had come out with new models. Apple released the first generation Macintosh, which was the first computer to come with a graphical user interface(GUI) and a mouse. The GUI made the machine much more attractive to home computer users because it was easy to use. Sales of the Macintosh soared like nothing ever seen before. IBM was hot on Apple's tail and released the 286-AT, which with applications like Lotus 1-2-3, a spreadsheet, and Microsoft Word, quickly became the favourite of business concerns.
That brings us up to about ten years ago. Now people have their own personal graphics workstations and powerful home computers. The average computer a person might have in their home is more powerful by several orders of magnitude than a machine like ENIAC. The computer revolution has been the fastest growing technology in man's history.

Friday, 22 January 2016

fact of brahma marrige



Saraswati Puja, Saraswati Puja, Saraswati Pooja, Saraswati Pooja ...


Below is the Trio – Brahm,Vishnu and Mahesh.So there are different ...Brahma marriage is regarded as the purest form of marriage in Hindu religion. As per the traditions of this marriage, the father gives his daughter to a man of learning and good character. The daughter is richly dressed and adorned with ornaments and is offered as a kind of gift, also referred as 'danam' to a man having good character and high learning, also known as 'srutisilavan'. It is considered to be the most honourable type of marriage according to the Smritis. The existence of Brahma marriage can be traced back to the Vedic era

Eligibility of Brahma Marriage 
A Brahma marriage is a type of Indian marriage where a boy is able to get married once he has completed his student hood, or Brahmacharya. Brahma marriage has the most supreme position of the eight types of marriages. In ancient days, there prevailed gurukul system, where the boy goes to live with his guru to acquire knowledge and expertise. This stage isBrahmacharya or student-hood for the boy and he would be eligible to get married only once he completes his studies. 

Arrangement of Brahma Marriage 
Once the boy is ready to get married after acquiring all the expertise required his parents would approach the family of a matching and eligible girl. The father of the girl also carefully chooses the bridegroom who is well versed in Vedas and of a noble character. This is how a Brahma marriage is arranged. 

Rituals of Brahma Marriage 
The girl's family did not have to give any dowry to the boy's family. There was the ritual of kanyadaan which symbolizes that the father gifts his daughter to the boy. In this system of marriage no commercial transaction is done. Among the eight types, this is regarded as the highest type of marriage by the dharmashastras

This marriage is performed even before the girl has attained her puberty. The mantras are chanted while performing the marriage, which are addressed by the groom to the bride who comes to him. It was understood that a girl's marriage, which has same significance for her that the upanayana has for a boy, must be performed when she is seven years old (or eight years from conception). 

Sunday, 3 January 2016

Problem 9.8 Orthographic Projection

Problem 9.8 Orthographic Projection – Draw the Orthographic Projections of the object given below in 1stangle method of projection. (1) Front View (2) Top View (3) L.H. S.V.

Orthographic Projections - Engineering Drawing
Orthographic Projections - Engineering Drawing
Click on Image to Zoom

Procedure:

Step-1 Draw a horizontal x-y line of some suitable length. And x’-y’ line perpendicular to preciously drawn x-y line and give the point O at the intersection of the two lines.
Step-2 In this problem the Front View, Top View and Left Hand Side View have to be drawn in 1st angle method of projection, so first find out the total length, total height and total width from the isometric drawing given above. The total length is the length of the base of the front view, i.e., form X direction. The total height is the height in the front view and the total width is the length of the base in the side view.
Step-3 The total length is 105 mm, total height is 75 mm and the total width is 80 mm.
Step-4 Draw three boxes with light straight lines at respective location in such a way that the views should be in 1st angle method of projection. And these boxes should be at least 10 mm away from the x-y & x’-y’ lines.
Step-5 Then start the drawing by front view and within the respective box with dimensions, and it should be drawn with medium dark lines or curves. Like in this way draw all the required view and look for the hidden lines, which are drawn as dashed line. But the drawing should be drawn by transferring the projectors only wherever possible.
Step-6 Give the dimensions by any one method of dimensions and give the name of the views, as shown in the figure.

Right Hand Thumb Rule:

maxwell's corckscrew rule
The direction of magnetic field; in relation to direction of electric current through a straight conductor can be depicted by using the Right Hand Thumb Rule. It is also known as Maxwell’s Corkscrew Rule.
maxwell's corckscrew rule
If a current carrying conductor is held by right hand; keeping the thumb straight and if the direction of electric current is in the direction of thumb, then the direction of wrapping of other fingers will show the direction of magnetic field.


maxwell's corckscrew rule
As per Maxwell’s corkscrew rule, if the direction of forward movement of screw shows the direction of current, then the direction of rotation of screw shows the direction of magnetic field.
Properties of Magnetic Field:
  • The magnitude; of magnetic field increases with increase in electric current and decreases with decrease in electric current.
  • The magnitude of magnetic field; produced by electric current; decreases with increase in distance and vice-versa. The size of concentric circles of magnetic field lines increases with distance from the conductor, which shows that magnetic field decreases with distance.
  • Magnetic field lines are always parallel to each other.
  • No two field lines cross each other.


Magnetic field due to current through a circular loop:

maxwell's corckscrew rule
In case of a circular current carrying conductor, the magnetic field is produced in the same manner as it is in case of a straight current carrying conductor.
In case of a circular current carrying conductor, the magnetic field lines would be in the form of concentric circles around every part of the periphery of the conductor. Since, magnetic field lines tend to remain closer when near the conductor, so the magnetic field would be stronger near the periphery of the loop. On the other hand, the magnetic field lines would be distant from each other when we move towards the centre of the current carrying loop. Finally; at the centre, the arcs of big circles would appear as a straight lines.
The direction of magnetic field can be identified using Right Hand Thumb’s Rule. Let us assume that the current is moving in anti-clockwise direction in the loop. In that case, the magnetic field would be in clockwise direction; at the top of the loop. Moreover, it would be in anticlockwise direction at the bottom of the loop.
Clock Face Rule: A current carrying loop works like a disc magnet. The polarity of this magnet can be easily understood with the help of clock face rule. If the current is flowing in anti-clockwise direction, then the face of the loop shows north pole. On the other hand, if the current is flowing in clockwise direction, then the face of the loop shows south pole.
Magnetic field and number of turns of coil: Magnitude of magnetic field gets summed up with increase in the number of turns of coil. If there are ‘n’ turns of coil, magnitude of magnetic field will be ‘n’ times of magnetic field in case of a single turn of coil.

Magnetic Field due to a current in a Solenoid:

Solenoid is the coil with many circular turns of insulated copper wire wrapped closely in the shape of cylinder.
A current carrying solenoid produces similar pattern of magnetic field as a bar magnet. One end of solenoid behaves as the north pole and another end behaves as the south pole. Magnetic field lines are parallel inside the solenoid; similar to a bar magnet; which shows that magnetic field is same at all points inside the solenoid.
By producing a strong magnetic field inside the solenoid, magnetic materials can be magnetized. Magnet formed by producing magnetic field inside a solenoid is called electromagnet.

Next

Electromag Induction


The atoms in insulating materials have very tightly-bound electrons, resisting free electron flow very well. However, insulators cannot resist indefinite amounts of voltage. With enough voltage applied, any insulating material will eventually succumb to the electrical “pressure” and electron flow will occur. However, unlike the situation with conductors where current is in a linear proportion to applied voltage (given a fixed resistance), current through an insulator is quite nonlinear: for voltages below a certain threshold level, virtually no electrons will flow, but if the voltage exceeds that threshold, there will be a rush of current.
Once current is forced through an insulating material, breakdown of that material’s molecular structure has occurred. After breakdown, the material may or may not behave as an insulator any more, the molecular structure having been altered by the breach. There is usually a localized “puncture” of the insulating medium where the electrons flowed during breakdown.


Thickness of an insulating material plays a role in determining its breakdown voltage, otherwise known asdielectric strength. Specific dielectric strength is sometimes listed in terms of volts per mil (1/1000 of an inch), or kilovolts per inch (the two units are equivalent), but in practice it has been found that the relationship between breakdown voltage and thickness is not exactly linear. An insulator three times as thick has a dielectric strength slightly less than 3 times as much. However, for rough estimation use, volt-per-thickness ratings are fine.

                  

Faraday's Law

Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil. No matter how the change is produced, the voltage will be generated. The change could be produced by changing the magnetic field strength, moving a magnet toward or away from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc.
Further comments on these examples
Faraday's law is a fundamental relationship which comes from Maxwell's equations. It serves as a succinct summary of the ways a voltage (or emf) may be generated by a changing magnetic environment. The induced emf in a coil is equal to the negative of the rate of change of magnetic flux times the number of turns in the coil. It involves the interaction of charge with magnetic field.
Lenz's lawAC coil example
Faraday's Law and Auto Ignition
Index

Faraday's Law concepts
 
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Lenz's Law

When an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it. The induced magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant. In the examples below, if the B field is increasing, the induced field acts in opposition to it. If it is decreasing, the induced field acts in the direction of the applied field to try to keep it constant.

                    faraday laws