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.

 

          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.

 

         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. 

          A multimeter is an instrument that measures the voltage, current, and resistance of an electrical device. Also known as a VOM (Volt-Ohm-Milliammeter), they are very useful in providing field measurements or detecting faults with accuracy.

          The first multimeter was invented by Donald Macadie, a British post office engineer who was unhappy with the need to carry separate instruments needed for the maintenance of telecommunication circuits. His invention was the instrument that could measure amperes, volts and ohms, and was named the avometer.

          The device is commonly used by electricians and other experts to troubleshoot problems on appliances, motors, circuits, power supplies and wiring systems. They could use the device on batteries, switches, power sources etc for measuring or diagnosing.

            Multimeters can be analogue or digital. Analogue multimeters are cheaper, but their readings are not as accurate as the digital meters. Recent digital multimeters are advanced enough to measure extremely tiny differences or fluctuations. 

        An ohmmeter is an electrical instrument used to measure resistance of a conductor. Resistance, as we have already seen, is the opposition offered by a substance to the current flow in the device. The unit of measurement for resistance is in ohms; hence the tool to measure it is called an ohmmeter.

        One must know that every device has a resistance, large or small. Resistance in conductors increases with temperature, but decreases in the case of semiconductors.

        Depending on the application, there are micro ohmmeters, milli ohmmeters, and mega ohmmeters used. A micro ohmmeter measures extremely low resistances with high accuracy whereas a milli ohmmeter measures the same and confirms the value of any electrical circuit. A mega ohmmeter measures large resistance values.

        There is a device called Fluke micro ohmmeter. It is used to measure voltage, current, and test diodes.

 

          In simple terms, an oscilloscope is a type of equipment that provides visual images of varying electrical quantities. That means that its main function is to graph an electrical signal as it changes over time. Most oscilloscopes produce a two dimensional graph showing time on the x-axis, and voltage on the y-axis. The signals produced are plotted on a graph.

         There are a number of applications for which oscilloscopes are used. Most of the general purpose instruments are used for maintenance of electronic equipment and laboratory work. It is an important tool for designing, or repairing electronic equipment. Special purpose oscilloscopes are used for analyzing an automotive ignition system or to display the waveform of the heartbeat as an electrocardiogram.

         Oscilloscopes can be divided into two - digital and analogue. Digital oscilloscopes are portable units that are replacing the analogue ones.

Many scientists have, in the past, tried to study the features of charged particles, and the force they exert on other charged particles. But the reason behind this remained a mystery until the French physicist Charles Augustin de Coulomb put forward his theory on the same.

Coulomb’s law, as it is known all over the world describes the electrostatic interaction between electrically charged particles. This law was first published by Coulomb in 1783.

Let’s see what it says. Suppose there are two charged particles. With these is created an electric force. If the charges are stronger, the forces they create will be stronger too. This is the basic idea behind the law. Coulomb also found out that either attraction or repulsion acts along the line between the two charges.

A decade earlier, British scientist Henry Cavendish also made similar observations, but he did not publish them. So, most of the credit went to Coulomb alone.

Georg Simon Ohm was German physicist who formulated the ‘Ohm’s Law’.

       It states that current flow through a conductor is directly proportional to the potential difference or voltage, and inversely proportional to the resistance. The law was important, because it marked a successful start to the analysis of electric circuits.

         In 1827, Ohm published his book titled ‘The Galvanic Circuit Investigated Mathematically’ in which the Ohm’s Law first appeared.

         Although it was later treated as an important work that influenced the theory and applications of electricity, the book did not receive enough acceptances when it was published. It is said that Ohm resigned his post as a teacher from Jesuit Gymnasium of Cologne due to this.

        A few years later, Ohm’s Law started getting noticed, and Ohm was appreciated. In 1841, the Royal Society of London awarded him its prestigious the Copley Medal considering his contribution.

        The physical unit measuring electrical resistance ‘ohm’ was named after him.