My Science School

          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. 

          The concept of electricity cannot be complete without Faraday’s Law of induction. It describes how changing magnetic fields can cause electric current to flow in a conductor.

          The working principles of electric motors, transformers, generators, are all based on Faraday’s Law of Induction.

          Faraday discovered electromagnetic induction in 1831. He had conducted many experiments before concluding his theory. He experimented with magnetic fields that stayed the same, and realized that they do not induce current. Then he experimented by changing magnetic fields, and saw that they induced current and voltage.

          Faraday’s discovery of electromagnetic induction did not receive much acceptance from scientists when it was introduced. But Scottish scientist James Clerk Maxwell realized its importance, and used the ideas as the basis of his quantitative electromagnetic theory.

       Maxwell’s equations refer to a set of four equations that describe the creation and propagation of electric and magnetic fields. They are named after the Scottish physicist James: Clerk Maxwell, who made significant contributions to unify the theories of electricity, magnetism, and light. The early form of these equations was published between 1861 and 1862, and it proposed that light is an electromagnetic phenomenon.

       The equations formed from these laws could give an explanation to many phenomena around. For instance, how hair stands on end when one removed a nylon sweater, how a compass needle points north all the time, how a power station turbine generates electricity etc. Together, they could also describe the transmission of radio waves, and the propagation of light.

       Hence, Maxwell’s equation, along with the Lorentz force law, is said to form the foundation of classical electromagnetism. Lorentz force law describes the force acting on a moving point charge ‘q’ in the presence of electromagnetic fields. 

        A power station is a place where electricity is produced on a large scale for distribution. It is also called a power plant, or power house.

       The electricity generated here, mostly in several thousand watts, is transmitted to power grids through power lines. It is from these grids that people get electricity for homes, schools, businesses etc.

       A majority of the power stations in the world burn fossil fuels to generate electricity. This includes coal, oil, and natural gas. They are called thermal power stations.

       There are also plants that use nuclear power instead. It is said that over 11 per cent of the world’s power is produced by nuclear power stations.

      

Continue reading "What are power stations? "

      Hydroelectric power plants use the force of falling water to generate electricity. It’s one of the safest sources of energy that is also reliable and cheap.

      Some of the earliest hydroelectric power plants were set up in and around London. In the 1870s, English industrialist William George Armstrong built one such plant at Crag-side, in England. This was perhaps the world’s first hydroelectric power scheme. It used water from the lakes on his estate to power the generator.

        In 1882, a central station was built In Godalming, England, using hydroelectric power. This time, it was to provide street and household lighting to the public. But this project ended up as a failure.

       However, many hydroelectric projects were conceived all over the world by then. It is said that in 2015, hydro power generated 16.6 per cent of the world’s total electricity. Almost 150 countries have hydro power plants today, with China being the largest producer of hydroelectricity. 

        The ‘War of Currents’ was the term used to refer to the dispute between two brilliant inventors - Thomas Alva Edison and Nikola Tesla. It happened towards the end of the 19th century, when there arose a question over which was better-direct, or alternating current.

        Edison was the brains behind the development of DC, which ran continually in a single direction. In the early years of electricity, DC was regarded as the standard. But it had a problem; it couldn’t be easily converted to higher or lower voltages.

       Tesla strongly believed that alternating current was a solution to this. AC, which he co-developed could reverse its direction unlike DC, and could also be converted to different voltages using an electrical transformer. It made possible long distance electricity transmission too.

       However, Edison saw Tesla’s argument as a threat to his work. He thus started off a public campaign, trying to discredit AC. The main reasons for the campaign was that Edison did riot want to lose the royalties he had been earning from his DC patents.

      But in spite of all the efforts Edison made, it was Tesla and his AC that won in the end. Today, electricity is mainly powered by alternating current.

 

A thermal power station is where heat energy is used to generate electricity. It is the most conventional, and common source of electric power.

Let’s see how it works. A thermal power plant burns fossil fuels like coal, oil, and natural gas to produce steam. The steam thus formed, creates a pressure that spins the turbine inside the plant. Electric power is generated by these spinning turbines.

The advantages of a thermal power plant is that it requires less initial cost, and less land compared to other power stations. The fuel used - fossil fuel- is also cheap. Many countries in the world depend mainly on thermal power for electricity. It is said that around 40 per cent of the world’s power is made out of fossil fuels.

However, thermal power plants have been criticized for the pollution they cause, due to the large amount of smoke and carbon dioxide emitted. This is a cause of global warming. Besides, the overall efficiency of a thermal power station is below 30 per cent. 

         As we saw earlier, hydroelectric power plants make use of the force of flowing water to generate electricity. There are many reasons why experts hold that hydroelectricity is more acceptable than the other. One of the most significant advantages is that hydroelectric power plants do not require any fuel for power production. They only need water, a renewable source of energy. Thermal power stations need fossil fuels like coal, natural gas, oil etc., to function.

         Since no fuel is required, the cost of electricity produced by hydroelectric plants is also somewhat constant. In the case of other kinds of plants, it depends on the cost of fuels in the international market.

         Another important factor is pollution. Hydroelectric power plants do not burn fuel; hence do not cause pollution either. The heated water that comes out of them threatens aquatic lives too.

         Hydroelectric plants also have longer lives compared to thermal plants. Besides these, hydroelectric plants are known to facilitate irrigation of farms and preventing floods.

         Hence, around 150 countries in the world use this technology for power generation.

 

       As we know, it is flowing water that creates the energy required to generate electricity. Wonder how it works?

      Well, there is a huge amount of energy created from the falling of water. This energy is harnessed by forcing it through a pipe, which is called a penstock. At the end of the pipe, there is a turbine propeller. So, when water flows through the pipe, it reaches the propeller, and turns the blades of the turbine. This spins an electric generator. Hence, as long as water is flowing, the generator will be spun, and there will be electricity.

      There are mainly three ways in which hydroelectric plants are designed.

       The most common type follows a storage system. To put it clearly, there is a dam used in this system. It slows the flow of a river and stores the water in a reservoir above it. When needed, a portion of the water is released into the river flowing below the dam. The pressure thus created from the fall of water, spins turbine generators lying below. From this is created hydroelectricity.

 

Continue reading "How is electricity produced in hydroelectric power stations? "

       Osmotic power is the energy that comes out of the difference in salinity between sea water and fresh water. This energy can be harnessed to generate electricity.

        Sounds strange, doesn’t it? Let’s see how this happens. When we separate fresh water from sea water by a semi permeable membrane, we can see that the fresh water moves through the membrane into the sea-water. This happens by a process called osmosis. It means the movement of something from a less concentrated solution into a concentrated one.

        There is a pressure created by the process of osmosis. This pressure combined with the permeating flow rate together, turns a hydraulic turbine, and produces electricity.

        Statkraft, the Norwegian energy firm was the world’s first test plant that harnessed osmotic power. Experts note that there are many advantages to this kind of power production over others. However, the biggest challenge this technology faces is the cost. Osmotic power plants are just too expensive to install.

        Yet another renewable energy is biomass, a fuel that is developed from organic materials like certain crops, manure, forest debris etc. In biomass power plants, waste is burned to produce steam that runs a turbine, producing electricity. 

Dr. Vasant Ranchhod Gowarikar (25 March 1933 – 2 January 2015) was an Indian scientist. He was the chief of Indian Space Research Organization and also the scientific advisor to the Prime Minister of India in 1991–1993.Gowarikar made valuable contributions to the fields of space research, weather and population. He was well known for his monsoon forecast model as he was the first scientist to develop an indigenous weather forecasting model that predicted the monsoon correctly.

Awards

• Gowarikar was awarded Padma Shri in 1984


• Padma Bhushan in 2008.


•  He also received the Fie Foundation Award.

Career

He had worked with the Indian Space Research Organization  Gowarikar was involved in space research in early career under Vikram Sarabhai when his office was in the building of the local St Mary Magdalene Church in Thumba in Kerala. He pioneered solid propellant development and later served as Director of the Vikram Sarabhai  Space Centre (VSSC) between 1979 and 1985.

Gowarikar also served as the scientific advisor to Prime Minister of India P.V. Narasimha Rao from 1991 to 1993. He had also been the Secretary of Department of Science and Technology.

He was appointed as Vice-Chancellor,Pune University and was chairman of the Marathi Vidnyan Parishad between 1994 and 2000. Gowarikar, along with his associates, also compiled The Fertilizer Encyclopedia (2008) that featured 4,500 entries detailing the chemical composition of fertilizers, and containing information on everything from their manufacturing and application to their economic and environmental considerations.

To read more about Vasant Gowarikar Click https://en.wikipedia.org/wiki/Vasant_Gowarikar