My Science School

          The first recorded discovery about the relation between electricity and magnetism was made by Hans Christian Orsted in 1820.

           During an experiment, he noticed that the needle on his compass pointed to a different direction, when a battery near it was turned on. 

 

                                                                                                                                                                                                                                                                                                                      In 1824, William Sturgeon invented an electromagnet. It was made of a horseshoe-shaped piece of iron, wrapped with copper wire. He found out that when current was passed through the wire, it attracted the pieces of iron, and when the electric flow stopped, the magnetization ended too.

 

                By the 1830s, the US scientist Joseph Henry improved the design of the electromagnet. He used an insulated wire, and placed thousands of turns of wire on a single core. This made a big change! With this attempt, electromagnets gained more popularity. 

 

 

 

            There are different waves of light and energy that move around us.

            They come in the form of heat in the atmosphere, or radiation from space, or in any other form. These energy waves are commonly known as electromagnetic radiation. They have electric, as well as magnetic characteristics.

            The scientific definition given to this by experts goes as follows - the energy that is propagated through free space or a material medium in the form of electromagnetic radiation.

            Other than visible light, electromagnetic radiation includes radio waves, microwaves, infrared waves, ultraviolet rays X-rays, and gamma rays. They are classified on the basis of their frequencies or wave-lengths. The fact that the electromagnetic radiations are related to electromagnetism was put forward by a few scientists in the past. The existence of electromagnetic waves was first predicted by the Scottish physicist James Clerk Maxwell. In his electromagnetic theory that he put forth in 1864, he said that light is an electromagnetic disturbance in the form of waves.

           A few years later, German physicist Heinrich Hertz applied Maxwell’s theories to prove the existence of electromagnetic waves. 

          In its simplest terms, electromagnetic induction can be defined as the process where a conductor placed in a changing magnetic field causes the production of voltage across the conductor. This, in turn, causes or ‘induces’ an electric current.

         Many electrical devices that we see daily work on the principle of electromagnetic induction. A common use of this can be seen in electrical generators, transformers, induction cookers, musical instruments etc. The concept of electromagnetic induction was put forth in the early 1830s by the English physicist Michael Faraday.

           He conducted many experiments to study the idea. In one of it, he used a coil of wire, a permanent magnet and a device to detect voltage in the wire. When Faraday passed the magnet through the coil of wire, he saw there was a voltage induced and therefore current too. But it soon disappeared when the magnet stopped moving. From this, Faraday made a few observations. The most important one was that the induced voltage is the result of a changing magnetic field.

           In other words, Faraday discovered a way to produce electrical current by using the force of a magnetic field.

           The voltage induced is known as the electromotive force, or emf.

           Faraday’s findings led to a law linking electricity and magnetism known as the Faraday’s Law of Electromagnetic Induction. 

Thales of Miletus is an important figure in the history of electricity. It is said that he discovered static electricity around 600 BC.

Static electricity was first observed when amber, rubbed with animal fur, got charged, and attracted light objects such as dry leaves, or bits of straw. Even though other people may have noticed this before, it was Thales who first recorded his findings. But Thales has never identified it as static electricity. At that time magnetism was also confused with static electricity.

Later, it was proved that the force that works between amber and animal fur is nothing but static electricity. Thales’ role was remarkable because he was the first to record his findings regarding static electricity. Thales was born in the city of Miletus around the mid 620 BC. He was a philosopher, and astronomer and the one who conducted the earliest studies in electricity. Thales’ findings were recorded but none of them survived to modern times. 

          Otto von Guericke was a German scientist, and inventor who lived between 1602 and 1686.

          He is credited to have made many inventions at a time when there were not many resources to refer to. One of it is the electrostatic generator, known to be the first one ever made.

          It was described as a huge sulphur ball, mounted on a pole inside a glass globe. With the help of a hand crank, the ball was rotated. As a result, the ball rubbed against a pad, generating sparks. This was static electricity, a phenomenon which they could not identify then. But the device became famous, and was used for later experiments with electricity.

            In 1672, Guericke found out that electricity produced through his earlier experiment could cause the surface of the sulphur ball to glow. The concept of electrostatic repulsion was demonstrated for the first time in history through Guericke’s book. 

          The simplest definition for the relay is that it is an electrically operated switch. The device is used where it is necessary to control a circuit by a low-power signal or where a number of circuits have to be controlled by one signal.

          Relays are controlled by electric current, magnetism or temperature. There are two types of relays - electromechanical and solid state. In the former, contacts are opened and closed using a magnetic force. With solid state relays, switching is done electronically.

          Electromechanical relays are general purpose relays. They are more common because they have lower cost, and can switch from AC or DC with equal ease.

     

Continue reading "Why did the relay make history? "

             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.