My Science School

             Stephen Gray was an English astronomer who made significant contributions to science. These include his experiments with conduction, insulation, and electrostatic induction.

           One of his experiments was done using a glass tube. Gray observed that when the glass was rubbed with a dry hand or dry paper, it obtained electric charge. As a result, it attracted a feather to the glass, as well as the cork with which it was closed. The cork was in fact, used to keep the dust out when not in use.

          From the experiment, Gray concluded that the ‘attractive virtue’ passed from the tube to the cork.

         To clear his doubts, Gray proceeded with a similar experiment. This time, he attached an ivory ball to a piece of wood, and inserted the other end of the wood into the cork. Once it was done, he confirmed that attraction and repulsion passed to the ball, that too stronger than that on the cork.

         Gray observed that substances like silk do not conduct electricity. And that Earth was somehow responsible for conducting electric charge away from the body.

         For his electrical experiments, Stephen Gray received the first Copley Medal instituted by the Royal Society, in 1731. However most of his works went unacknowledged and he died as a poor man.

 

          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.