Month: June 2020

The answer is YES !. The Sun rotation varies by latitude and it rotates on its own axis once in about 27 days. How was it possible to detect the rotation of a star of surface temperature about 5800 Kelvin and located at the center of the solar system which is about 152.03 million km away from the Earth ? Sun spots. Yes, Sun spots, as the name suggests,are the darker areas on the surface of the sun. Sun spots are areas where the magnetic field is about 2,500 times stronger than Earth’s. Because of the strong magnetic field, the magnetic pressure increases while the surrounding atmospheric pressure decreases.  This in turn lowers the temperature relative to its surroundings because the concentrated magnetic field inhibits the flow of hot, new gas from the sun’s interior to the surface thereby appearing darker.The number of sunspots has a cyclical increase and decrease over an approximately 11-year period known as the solar cycle. As these spots are located at the surface, they tend to move along solar disc validating the rotation of the sun on its own axis. Sun spots are not just the characteristic features of the sun. Their impact on Earth is indeed devastating. Increased sun spots correspond to increased solar activity which includes Coronal Mass Ejections(CME),solar flares and so on. These phenomena lead to geomagnetic storms, the increase in the Northern and southern lights and a possible disruption in radio transmissions and power grids.

Oscillation is a type of harmonic motion, typically periodic, in one or more dimensions. Elastic property of the material is the most important aspect for a solid to oscillate. However, elasticity is the property of a solid to regain its shape. How can these cause oscillations? Let us consider a spring hanging vertically downward with one end fixed at the wall. The spring is in equilibrium (no external forces acting on it). When we displace the position of the free end of the spring upward (contracting) or downward (stretching), the restoring force comes into play and tends to bring back the spring to its equilibrium position imparting a negative velocity. Inertia on the other hand tries to oppose any change in velocity. When the body reaches the equilibrium position, the negative velocity is maximum producing a negative displacement. The body then overshoots the position of equilibrium. The restoring force is positive (in a direction opposite to the direction of restoring force considered before) and it must now overcome the inertia of negative velocity. The velocity keeps decreasing until it reaches zero but by this time the displacement becomes large and negative where again restoring force comes into play and the tussle ensues. Thus the oscillation of a physical system results from two basic properties elasticity and inertia.

The cooling of one junction and the heating of the other when electric current is maintained in a circuit of material consisting of two dissimilar conductors. Peltier effect was discovered in 1834 by the French physicist Jean-Charles Athanase Peltier. The Peltier effect is the reverse phenomenon of the Seebeck effect. Seebeck effect is the conversion of temperature differences directly into electricity. This effect is named after German Physicist Thomas Johann Seebeck. In 1821, Johann Seebeck discovered that a compass needle would be deflected by a closed loop formed by two metals joined in two places, with a temperature difference between the junctions. This was because the metals responded differently to the temperature difference creating a current loop and a magnetic field. In 1834, Peltier found that an electrical current would produce a temperature gradient at the junction of two dissimilar metals when the current direction was reversed, the cold junction would get hot while the hot would get cold. Applying a current (e- carriers) transports heat from the warmer junction to the cooler junction.The Peltier effect can be used to create a refrigerator that is compact and has no circulating fluid or moving parts. Such refrigerators are useful in applications where their advantages outweigh the disadvantage of their very low efficiency. The Peltier effect is also used by many thermal cyclers, laboratory devices used to amplify DNA by the polymerase chain reaction (PCR). PCR requires the cyclic heating and cooling of samples to specified temperatures. The inclusion of many thermocouples in a small space enables many samples to be amplified in parallel.

What happens when we place hot coffee on a table ? As time passes, the temperature of coffee reduces so that it is equal to the surrounding temperature in which it is placed. The same mechanism is applied in refrigerators. The continuous flow of cold substance in refrigerators makes it a ‘surrounding of low temperature’ that it cools the object placed in it. So how to create this continuous flow ? A refrigerant ( Why not any other substance ? Refrigerant is a substance that can easily undergo phase transition) is passed through a compressor and its pressure is increased. As pressure increases, the temperature also raises due to decrease in volume. This superheated high pressure vapour is passed into the condenser coils( the zig zag wires at the back of refrigerators ) which reduces the temperature of the refrigerant to liquid phase. The high pressure liquid is then passed into the throttling device which is a small diameter spiral valve. When the liquid is passed into this small valve, the temperature reduces( the same way as the perfume that comes out of the small opening of a perfume bottle is found to be cooler). The cold liquid is then passed to the evaporator that is located inside the refrigerator. Through evaporator fans, the cooled air caused by the continuous flow of cooled liquid circulated throughout the refrgerator absorbing heat from the objects placed inside. On evaporation, the liquid undergoes phase change to low pressure vapour and is directed to the compressor. The cycle continues…

How about locating a scar in your hand. One can easily detect it by simply by looking at it with the help of one’s own eyes if that person doesnt have any vision related problems. How about locating a scar on one’s face. One needs to look for a mirror or a camera. How about locating a tumor in one’s body. Now one is in need of a special device to look into the body as one just cannot cut open or operate body every time. This special device is MRI (Magnetic Resonance Imaging). As its name suggests it uses magnetic field for imaging. Our body is made up of millions of atoms. These are in constant random motion. Especially there are a large number of water molecules which contain hydrogen that possess high magnetic moment, meaning it can align itself in presence of magnetic field. So, using magnetic field one can align the protons in one direction. When additional energy in the form of a radio wave is given, the magnetic vector gets deflected causing the hydrogen nuclei to resonate. Different slices of the body resonates with different frequencies. When the radio wave is turned off, the magnetic vector returns to the resting state and causes a signal to be emitted. These signals are used to create the MR images. In a nutshell, the mechanism of MRIs are more like a carbon copy paper where the force applied by the pen is the radiowave.