My Science School

            A transformer is an electrical device that works on electromagnetic induction to transfer electrical energy between two or more circuits. It is used in a wide range of power appliances to increase, or decrease voltage.

            We see transformers in almost every city. They are used to convert high-voltage electricity from incoming power lines, to lower-voltages.

         

Continue reading "Why is it said that the invention of the transformer was a turning point?"

            To put it simply, a transistor is an electronic component that can do two different jobs. It can act as an amplifier or a switch, depending on the need.

            As an amplifier, a transistor does the job of boosting current. That is, it takes in a tiny input current at one end and produces a bigger output current at the other end.

            It was at the Bell Laboratories in New Jersey that transistor was demonstrated for the first time. That happened on December 23rd, 1947. William Shockley, John Bardeen and Walter Brattain are the three persons credited with its invention.

            In 1956, they were awarded the Nobel Prize in Physics “for their researches on semiconductors and their discovery of the transistor effect”.

         In one of his experiments, Thomas Alva Edison discovered that electrons can flow from one metal conductor to another, through a vacuum. This discovery was later named as the Edison Effect.

         Sometime in the early 1880s, Edison and his team were working to find a light bulb filament. Their carbonized bamboo filament did well, but even so, carbon deposits were seen inside the bulb after hours. That was when he noticed that the carbon came from the end of the filament which was attached to the power supply. It looked as though it was flying through a vacuum onto the walls!

          Edison realized that there was electric charge flowing not just through the filament, but through the evacuated bulb as well.

          Although Edison was right about the flow, he could not find the reason behind it. He moved on to other experiments.

           Later, it was proved that Edison, with his experiment, discovered the basis of the vacuum tube. And the modified light bulbs were later used to control the flow of electrons through vacuum. 

          An electronic amplifier is a tool that can amplify or increase the power, current, or voltage of a signal. It could be either a separate piece of equipment, or an electrical circuit within another device, but in general, amplifiers are used in almost all electronic equipment that we see around. They are particularly used in wireless communications and broadcasting.

          Before the amplifiers were introduced, mechanically coupled microphones were used to serve the purpose in telephone repeaters.

          In 1906, the triode was invented. It was the first electronic device that could amplify signals. It is a fundamental form of vacuum tube developed by the American inventor Lee De Forest. He had only a little understanding of how the tube worked.

          However, the discovery revolutionized electrical technology, and laid the foundation of electronics. It also made possible radio broadcasting, talking motion pictures, and countless other applications.

 

         Different kinds of electric lamps were invented by masters in the past.

         The English inventor Humphrey Davy’s electric arc lamp was one such creation that made great changes in the field of electricity and lighting.

         However, the arc lamps were not flawless. Their biggest disadvantage was that they were not fit for practical use. They emitted too much of light and also, burnt out quickly. Nevertheless, the principle of arc lamps was used till the 1900s by various inventors for developing electric lights and bulbs. Among them were Warren de la Rue and William Staite.

            In 1840, the British scientist Rue developed a light bulb using coiled platinum filament instead of copper. Staite, on the other hand, had been working on increasing the longevity of conventional arc lamps. In 1848, he developed a clockwork mechanism. Through this, he was able to regulate the movement of the carbon rods used in the lamps that eroded very quickly. 

Rajeev Motwani (March 26, 1962 – June 5, 2009) was a professor of Computer Science at Stanford University whose research focused on theoretical computer science. He was an early advisor and supporter of companies including Google and PayPal, and a special advisor to Sequoia Capital. He was a winner of the Godel Prize in 2001.

Education

Rajeev Motwani was born in Jammu and grew up in New Delhi. His father was in the Indian Army. He had two brothers. As a child, inspired by luminaries like Gauss, he wanted to become a mathematician. Motwani went to St Columba’s School, New Delhi. He completed his B.Tech in Computer Science from the Indian Institute of Technology Kanpur in 1983 and got his Ph.D. in Computer Science from the University of California, Berkeley in 1988 under the supervision of Richard M. Karp.

Fields

• Theoretical computer science


• Data privacy


• Web search


• Robotics


• Computational drug design

Awards

• Godel Prize in 2001


• Okawa Foundation Research Award


• Arthur Sloan Research Fellowship


• National Young Investigator Award from the National Science Foundation


• Distinguished Alumnus Award from IIT Kanpur in 2006


• Bergmann Memorial Award from the US-Israel Bi-National Science Foundation


• IBM Faculty Award

To read more about Rajeev Motwani Click https://en.wikipedia.org/wiki/Rajeev_Motwani

        The story of the invention of the electric bulb was very interesting. Even though many believe that it is Thomas Alva Edison who discovered the light bulb, it was not so. He played a major role in the development of the light bulb, and its popularity. The story of the light bulb begins long before Edison patented the first commercially successful bulb in 1879.

          Alessandro Volta’s invention of the battery in 1800, gave inspiration to many scientists. One among them was Humphrey Davy. He produced the world’s first electric lamp by connecting voltaic piles to charcoal electrodes. It cannot be called an electric bulb as such. It was an electric arc lamp, and he introduced it in 1802. It was named so for the bright arc of light emitted between its two carbon rods. However, Davy’s arc lamp wasn’t a very practical source of lighting. It was much too bright for use in a home, and it burned quickly. But the principles behind this arc light were used throughout the 1800s, and many took inspiration from this invention.

          Another person who made significant contributions to the making of the electric bulb is Sir Joseph Wilson Swan.

          Swan was an English chemist. During the 1850s and 1860s, he conducted many experiments on bulbs using carbon filaments. Most of them failed, because the vacuum pumps used in those times were not good, so they couldn’t remove enough air from the lamps. Besides, the lamp deposited a dark layer of soot in its inner surface. This obscured the light.

          In 1878, Swan demonstrated an improved working lamp. It had a better vacuum, and carbonized thread as a filament. The method of processing was such that the bulb avoided early blackening. Soon after the demonstration, Swan was granted a UK patent. After that, light bulbs were installed in homes in England. In 1880, he received a US patent too.

              For his contributions, Swan was knighted in 1904. The same year he also received the prestigious Hughes Medal, instituted by the Royal Society of London. 

          We saw that during the 1800s, many inventors have worked hard to develop an effective light bulb. But, the most successful among these inventors was Thomas Alva Edison.

          Edison’s serious research into making a practical incandescent lamp began around 1878. He wanted to invent a safe, yet cheap electric light that could replace the earlier ones. Between 1878 and 1880, he conducted many experiments, with carbon filaments, platinum, and other metals. In 1879, he successfully tested a bulb with a carbon filament that lasted 13.5 hours.

          The following year, Edison and his team discovered that a carbonized bamboo filament could last over 1200 hours. This marked the beginning of commercially made light bulbs in 1880.

          As we know, this is just one of the many inventions made by Edison.

          Thus, Edison’s contributions remain unparalleled and, for his tireless work, he was rightfully described as one of the greatest inventors. 

Scientists and inventors have used a number of filaments for incandescent bulbs in the past. But today, the most popular one is the tungsten filament.

It was William David Coolidge, who developed a method to manufacture tungsten filaments in 1910.

The biggest advantage of tungsten was that it had a high melting point, and was able to withstand heat and corrosion. That is exactly what attracted inventors to it. Besides, using inert gases inside the bulb increased its luminescence.

As years passed, the element was used in other lamps too, including halogen, fluorescent, mercury vapour etc. Tungsten is perhaps the most durable type of filament used in bulbs even today.

It is said that Thomas Alva Edison himself knew that tungsten would prove to be the best choice for filaments. But in his day, the technology and machinery required to produce the wire in fine form was not available.

          As you may already know, incandescent and fluorescent are two types of light bulbs commonly used for various lighting applications.

          Incandescent light bulbs are older, but are still used in our houses. They come in the form of a glass sphere, with a very thin filament inside. It is the tungsten filament that we mostly use now, and it is surrounded by an inert gas. In these bulbs, light is produced by heating the metallic filament until it starts to emit light.

         A fluorescent bulb is totally different. It is a glass tube coated with phosphorous, containing mercury vapour. When the gas inside is excited, these lamps produce light. Unlike incandescent lights, they come in different shapes and sizes.

 

Continue reading "How is a fluorescent lamp different from an incandescent lamp? "

        A compact fluorescent light (CFL) bulb or lamp is a type of fluorescent lamp that is designed to replace incandescent lamps. They are known by different names - as compact fluorescent light, or energy-saving light, or as compact fluorescent tube. CFLs come in different shapes and forms, and are primarily known for their effectiveness and long life.

        The modern, spiral shaped CFL bulb that we use today in our houses was developed by Edward Hammer in the late 1970s.

        Although there are different reasons why people use CFLs, the most important feature of these lights is their ability to save energy. It is said that they consume 75 per cent less energy compared to incandescent lamps.

        Compared to ordinary lights, CFLs are more expensive, but they last longer. One can use them for months together, but not ordinary bulbs.

 

 

         An ammeter is an instrument used to measure the flow of electric current in a circuit. It measures current in terms of amperes, which is the unit of current. The speed and force of a current can be measured using this instrument.

         In the past, the instrument relied on the Earth’s magnetic field to take the readings of current. But as technology improved, better ammeters were designed and developed. Ammeters are mostly used in science laboratories. Other than scientists, electricians also use this instrument, to check the electric circuit.

        There are smaller units of reading to amperes, namely, milliamperes and microamperes. These are measured using milliammeters and microammeters respectively.

        There are two types of ammeters - analogue and digital. In analogue ammeters, there is a needle that points to the reading. In digital ammeters, they are displayed digitally.

 

        A voltmeter is an instrument that measures the voltage between two points in an electric circuit. It can be connected to a circuit by joining its positive and negative wires to where the voltage is. With such an arrangement, the instrument is said to be parallel to the electrical circuit.

       A voltmeter can be used for many purposes. For instance, to check whether there is any more electricity left in a battery.

       In an analogue voltmeter, the pointer indicates the number of volts. In a digital voltmeter, the reading will be displayed digitally. There are also voltmeters that can be mounted on a transformer, and other huge devices.

       Yet another variety is a voltmeter that uses amplifiers in them. Such meters can measure very small, or tiny voltages of microvolts, or even less.

 

         A galvanometer is a tool that measures the flow of electric charges through a wire. This basic device consists of a coil placed in a magnetic field. It can be used for detecting and comparing small electric currents.

        The ideas of galvanometers are known to have developed from an observation made by Hans Orsted in 1820. He had found out that the needle of a magnetic compass deflects near a wire that has electric current passing through it. But it was Johann Schweigger who built the first sensitive galvanometer in the same year. Galvanometers, since then, came to commercial use.

        A galvanometer can be used as an ammeter, as well as a voltmeter. By connecting a shunt in parallel to the coil, it acts an ammeter, and if the shunt is connected in series with the galvanometer coil, it becomes a voltmeter.