My Science School

         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.

 

 

         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.