My Science School

          A Leyden jar was the first device that could store electric charge. It was a glass jar with metal foil wrapped to its inside and outside surfaces. The jar would be partly filled with water, and had a wire running into it through the top part of the jar.

          There are two names involved with the invention of the jar. One is Ewald G. von Kleist, a German inventor who is said to have accidentally created it in 1745. The other is Pieter van Musschenbroek of Leyden, Holland, who ‘discovered’ the same thing in 1746. The latter invention spread through the world quickly, and thus Pieter gained more popularity for the invention.

          At first, it was thought that the electric charge was stored in the water inside the jar. In the 1700s, Benjamin Franklin studied much about this and proved that charge was stored in the glass. Hence, the later versions of Leyden jars had just metal foil wrapped inside and outside the glass.

          Technically, a Leyden jar is the prototype of the modern day capacitor which is used in almost all electronic equipment today.

 

                Benjamin Franklin invented the lightning rod in 1749. A lightning rod is a metal rod mounted on top of elevated structures like a building, tree, ship etc.

                It is electrically bonded with a wire with the ground or ‘earth’ through an electrode. Such an object protect a structure while lightning strikes. The idea behind it is that when lightning hits the building or tree, it will strike the rod.

              As a result, the electric power from lightning will be conducted to the ground through the wire, instead of passing through the building or tree. Thus, the structure can be saved from electrocution.

             Historians say that lightning rods were used in ancient times, and were particularly seen in the Sri Lankan kingdom of Anuradhapura, thousands of years ago. However, in the modern age, it was Benjamin Franklin who introduced the idea to the world. His aim was to create a tool that could save people from the dangers of the natural phenomenon. Through a series of experiments including the famous one using kite, he created the ‘Franklin rod’. 

            An electric motor is a device that converts electrical energy into mechanical energy. It works on the principle of electromagnetism.

            The first electrical motor is known to have been invented by a Scottish monk Andrew Gordon, in the 1740s. His motor was a simple electrostatic device.

            Almost a century later, British scientist Michael Faraday explained the conversion of electrical energy into mechanical energy by means of electromagnetism. The motor he created through the experiments was primitive, but it paved the way for later inventions. In 1822, British physicist Peter Barlow invented the first device to be powered by electromagnetism – known as Barlow’s Wheel.

            A decade later, British scientist William Sturgeon developed the first machine to be run on direct current. A few years after that, inventor Moritz Jacobi created the first real rotating electric motor that developed a remarkable mechanical output power. Frank Julian Sprague was the first to introduce a constant speed electric motor.

            All these have together contributed to the advancement of engineering technology in the world.

        Fuel cells are devices that generate electric current through chemical reactions. To put it better, a fuel cell uses chemical energy of hydrogen (or another fuel) to produce electricity in a clean and efficient manner. Its only products are electricity, heat, and water, and hence it is clean.

            There are a wide range of applications for which fuel cells can be used. This includes transportation, emergency power back up, material handling etc. compared to other technologies, fuel cells have many advantages. They are more efficient, and have lower emissions. That is, they do not emit dangerous substances like carbon dioxide or air pollutants, as their only products are water and heat. Yet another advantage is that fuel cells operate in a silent manner.

            The history of fuel cells began with the Welsh physicist Sir William Grove. In 1839, he demonstrated the first crude fuel cells. Although many people have tried to work on the concept of converting chemical energy into electric power, most of them were unsuccessful due to lack of resources.

            The first successful fuel cell was developed by the British engineer Francis Bacon in 1932, using hydrogen, oxygen, an alkaline electrolyte and nickel electrodes.

 

            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. 

        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.