Har Gobind Khorana


Har Gobind Khorana (9 January 1922 – 9 November 2011), was an Indian-American biochemist who shared the 1968 Nobel Prize for Physiology or Medicine with Marshall W. Nirenberg and Robert W. Holley for research that showed how the order of nucleotides in nucleic acids, which carry the genetic code of the cell, control the cell’s synthesis of proteins. Khorana and Nirenberg were also awarded the Louisa Gross Horwitz Prize from Columbia University in the same year.



Khorana was born in Raipur, British India (today Tehsil Kabirwala, Punjab, Pakistan) and later moved to become an Indian citizen after the partition of 1947. 



Fields 




  • Molecular biology



Institutions




  • MIT (1970–2007)

  • University of Wisconsin, Madison (1960–70)

  • University of British Columbia (1952–60)

  • University of Cambridge (1950–52)

  • Swiss Federal Institute of Technology, Zurich (1948–49)



Notable awards




  • Nobel Prize in Medicine (1968)

  • Gairdner Foundation International Award (1980)

  • Louisa Gross Horwitz Prize

  • ForMemRS (1978)

  • Albert Lasker Award for Basic Medical Research

  • Padma Vibhushan

  • Willard Gibbs Award



 To read more about Har Gobind Khorana  Click https://en.wikipedia.org/wiki/Har_Gobind_Khorana


Why do we use AC supply in our homes?

          Initially, direct current was used for power transmission. It was only in the 1950s that people realized the merits of alternating current over the other.

          Although the two are used today, alternating current is more accepted worldwide. It is used for bigger appliances as well as in houses. Let us see why.



          One of the main reasons for having AC for domestic purposes is that it causes very low wastage of power. It is seen that even at high voltages above 110 KV, less energy is lost in transmission. Yet another peculiarity of AC electricity is that voltage can easily be changed from high voltage to low and vice versa. This in turn makes it suitable for long distance transmission, unlike DC.



            Alternating current is also known to be capable of powering electric motors. Thus, it is useful for high-end appliances like refrigerators, televisions, computers etc.



            In terms of safety too, AC is preferred to DC power.



            It is for these reasons that most countries in the world favour AC than DC power. 


Why is it said that there are two types of batteries?

         Batteries can be broadly divided into two - primary and secondary.



         Primary batteries are single-use batteries - that are they can be used only once. After that, they should be discarded. They cannot be recharged. Quite a few non-rechargeable batteries are used in our daily life. This includes batteries used in toys, radios, remote controls, flashlights, clocks etc.



         Those batteries that can be recharged and reused are called secondary batteries. Through electric current, these batteries can be recharged.



         Secondary batteries can be seen in many devices including cell-phones, MP3 players etc.



         Yet another example can be seen in cars and trucks. Did you know that there is a lead-acid battery that works every time we start a car? This is how the car gets energy to run the lights and radio when the engine is not running. The battery in the car is recharged while we drive.



         Besides lead-acid, there are other batteries that can be recharged. This includes the nickel-cadmium battery, lithium-ion battery, nickel-metal hydride batteries etc.




Why is it said that a battery is the most popular source of electricity?

          A battery is a device that stores electricity in chemical form inside a closed-energy system.

          Long before the invention of electrical generators and grids batteries proved to be the main source of electricity, and still continue to serve this purpose.



          There are batteries in different shapes. Some are very small, like the ones used in wristwatches, or smart phones, and some are as big as those used in cars and trucks. At the extreme, there are huge battery banks that are the size of rooms.



           All batteries have three parts- an anode (the negative side), a cathode (positive side) and an electrolyte, a liquid or gel that contains electrically charged particles called ions.



          When connected to an external circuit, the ions interact with the other two, and a chemical reaction takes place inside the battery.



          This reaction results in the generation of electric current. This is how batteries function and provide electric power to all appliances in our house including mobile, phones, laptops, flashlights etc.


Why is it said that the history of the battery is interesting?

           Batteries are devices that have been helping mankind for a long time. But nobody knows exactly when they were invented.

         An account of the earliest battery came in 1938 from Baghdad. The story goes that while constructing a railway line in the city, workers uncovered a pre-historic battery. Experts said that the battery belonged to the Parthian Empire, and was at least 2000 years old!



         Luigi Galvani, in 1786, was conducting an experiment when he accidentally touched a dead frog’s legs with two different metals. Suddenly the muscles of its legs contracted. He thought it was because of ‘animal electricity’. But his friend and fellow scientist Alessandro Volta didn’t agree. He guessed that the same effect would be produced if cardboard was soaked in salt water, instead of a frog’s leg. So, he stacked copper and zinc discs, separated by a cloth, and soaked them in salt water. He connected wires to either end of the stack.



                To his surprise, it produced stable current. Thus in 1800, Volta invented the ‘voltaic pile’, the first true battery that produced continuous and stable current. This is believed to have laid the foundation for the modern battery. 




Which is the first practical-purpose battery?

           The Daniell cell is perhaps the first practical purpose battery ever. It was an electrochemical cell developed by the English chemist John Daniell in 1836. The cell offered a long-lasting source of power.



           Let’s see how the cell works. Daniell cell, consist of a copper pot filled with a copper sulfate solution, in which was immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode. The earthenware barrier which is porous, allows ions to pass through, but keeps the solutions from mixing.



           This cell produces current like a voltaic cell does, but with more efficiency. It soon became the industry standard for use. A voltage of over one volt is produced by a Daniell cell. To get a little more voltage, one has to increase the concentration of the solution in which the electrodes are dipped.





 

What is meant by electromagnetism?

Electromagnetism is a basic force of nature. It is the creation of a magnetic field from the movement of electrical charges.

The basic characteristics of this force can be best defined through the example of a copper wire. When electric current is allowed to pass through the wire, it can attract, or magnetize pieces of iron or steel near it. That is, the electromagnetic force causes the attraction, as well as repulsion, of electrically charged particles.



There are two basic concepts behind electromagnetism. The first one is that, any moving charge produces a magnetic field because of its movement. The second one is that, a moving magnetic field can cause current to flow into a conducting loop. This means, if there is a moving bar magnet near a coil of wire that is connected to a meter, it can detect the current flow.



 


Why is the history of the electromagnetic theory interesting?


           The history of electromagnetism cannot be complete without a few names. Let’s take a look at a few of them.



           In 1820, Hans Christian Orsted, a professor at the University of Copenhagen, arranged an experiment for his students. He wanted to explain the heating of a wire by an electric current, and his experiment on magnetic property. For this, he used a compass needle mounted on a wooden stand. Suddenly, he noticed that every time the electric current was switched on, the compass needle moved. Orsted was surprised, and kept working on this for months to study how it happened. However, he was not successful. 



                                                                                                                                                                                                                                                                    But this experiment was taken further by another physicist in France named Andre-Marie Ampere. Through his study, he found out that wires with parallel currents attract each other, whereas those with anti-parallel current repel. He concluded that electricity can be governed by two sets of forces - electric and magnetic. 


Continue reading "Why is the history of the electromagnetic theory interesting?"

Why is it said that many of the phenomena that we witness in our daily life can explained by electro magnetic force?

         Electromagnetism is a phenomenon that works behind almost all forces on Earth. Perhaps the only exception is gravity. Its influence is such that experts believe modern life is run through the electromagnetic phenomenon. Let’s try to understand what this means.



          Take the case of an electric fan. Its motor works on the principle of electromagnetic induction, which keeps it rotating on and on. This in turn, makes the blade hub of the fan to rotate, blowing air. Another example is that of a loud speaker. It is the electromagnetic force that is responsible for the movement of the coil inside. This in turn, results in the production of sound that can be heard over a long distance.



        


Continue reading "Why is it said that many of the phenomena that we witness in our daily life can explained by electro magnetic force? "

What is an electromagnet?

          An electromagnet is a device that can create a magnetic field if electricity is allowed to pass through it.



We can understand it better by comparing it with an ordinary magnet. In normal magnets, magnetic power is always present. But in electromagnets, the magnetic power or field depends on electricity. It can be turned on or off, using a switch. Likewise, the strength of these electromagnets can also be increased by increasing the amount of electric current.



                 There are different parts for an electromagnet. It consists of a coil of wire, made mainly of copper, and a piece of metal. The wire should be wrapped around the metal piece. When electric current is allowed to flow into the wire, a magnetic field is created around the coiled wire, and the metal gets magnetized. This is how an electromagnet is created.



                 Today, almost all equipment that we use, have electromagnets in them.


Why is it said that the introduction of electromagnets was interesting?


          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. 



 



 



 


What is meant by electromagnetic radiation?

            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. 






 


What is electromagnetic induction?

          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. 


Why is it said that Thales of Miletus played a major role in the history of electricity?

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. 




Why is it said that the machine which produced static electricity for the first time was a turning point in history?

          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.