Daily Science LYF

Lightning and ThunderBolt -  On Earth, the lightning frequency is approximately 44 times per second or nearly 1.4 billion flashes per year  and the average duration is 0.2 seconds made up from many much shorter flashes (strokes) of around 60 to 70 microseconds. Many factors affect the frequency, distribution, strength and physical properties of a typical lightning flash in a particular region of the world. These factors include ground elevation, latitude, prevailing wind currents, relative humidity, proximity to warm and cold bodies of water, etc. Lightning   is a naturally occurring electrostatic discharge during which two electrically charged regions in the atmosphere or ground temporarily equalize themselves, causing the instantaneous release of as much as one Gigajoule of energy. This discharge may produce a wide range of electromagnetic radiation, from very hot plasma created by the rapid movement of electrons to brilliant fl...

Hydrogen Bomb or Thermo-nuclear Weapon- It is the weapon working on the principle of nuclear fusion . A hydrogen bomb is a second-generation nuclear weapon which is more compact and a lower mass makes it very powerful than the first-generation atomic bomb. NOTE-  The first test of a fission (" atomic ")  bomb  released an amount of energy approximately equal to 20,000 tons of TNT (84 TJ). The first thermonuclear (" hydrogen ")  bomb  test released energy approximately equal to 10 million tons of TNT (42 PJ). - So the Hydrogen bomb is 1000 times powerful than an atomic nuclear fission based weapon. Modern fusion weapons consist essentially of two main components: a nuclear fission  primary stage (fueled by U-235 or Pu-239) and a separate nuclear fusion secondary stage containing thermonuclear fuel: the heavy hydrogen isotopes deuterium(D2O)  and tritium(T2O) , or in modern weapons lithium deuteride(LiH) . For this reason, thermonuclear w...

What is Nuclear Fusion? - A reaction in which two or more lighter nuclei fuse to form a heavy nucleus and a large amount of energy is given out is called Nuclear fusion reaction. - Fusion is the process that powers active or main-sequence stars or other high magnitude stars. The Sun is a main-sequence star and thus generated its energy by nuclear fusion of hydrogen into helium. In its core, the sun fuses 500 million metric tons of hydrogen each second into Helium. -  It takes considerable energy to force nuclei to fuse, even those of the lightest element, hydrogen.  When accelerated to high enough speeds, nuclei can overcome this electrostatic repulsion and be brought close enough such that the attractive nuclear force  is greater than the repulsive Coulomb force. The strong  grow rapidly once the nuclei are close enough, and the fusing nucleons can essentially "fall" into each other and the result is fusion and net energy produced. The fusion of lighter nuc...

What is Nuclear Fission? - The reaction in which a heavy nucleus splits into two or more smaller nuclei with the evolution of a large amount of energy is called nuclear fission reaction. - The fission process often produces gamma photons , and release a very large amount of energy. - Nuclear   fission of heavy elements was discovered on December 17, 1938, by German Otto Hahn. - Fission  is a form of nuclear transmutation because the resulting fragments are not the same element as the original atom. - Many types of nuclear reactions  are currently known but Nuclear fission differs importantly from other types of nuclear reactions, in that it can be amplified and sometimes controlled via a nuclear chain reaction  (one type of general chain reaction ). In such a reaction, free neutrons  released by each fission event can trigger yet more events, which in turn release more neutrons and cause more fission. Nuclear Power Plant-   The most important us...

Tidal Energy- Due to the attraction of the moon on sea-water, water surface rises and falls, thus the waves are formed. These waves are called tidal waves and energy possessed by rising and falling water tides is known as tidal energy.  The rise of the sea-water due to gravitational pull of the moon is called high tide whereas the fall of sea-water is called low tide . The tidal waves in the sea build up and recede (rise and fall) twice a day. The enormous movement of water between high tides and low tides provides a very large source of energy in the coastal areas of the world. The tidal energy can be harnessed by constructing a tidal barrage or Tidal dam across a narrow opening to the sea.  At High tide, water flows from the sea into the reservoir and turns the turbine. At low tide, stored water flows out from the reservoir into the sea and turns the turbine. Limitations of the tidal energy-  The rise and fall of water during tides is not high enough to gene...

What is a Solar Cell?                                                            - It is a device to convert solar energy into electrical energy . These cells are made from semiconductor like silicon, gallium, germanium. Solar cells are also known as photovoltaic cells . The efficiency of solar cells made from these materials is about 10-15%. The modern solar cells are made of selenium and have an efficiency of about 25%. The principal advantage of solar cells are that they have no moving parts, require little maintenance and work without the use of the focusing device. Another advantage is that they can be set up in remote and inaccessible places easily where power transmission is expensive.  Construction - To make a solar cell, thin layers (also called wafers ) of a semiconductor having impurities are arranged in such a mann...

Transmission of heat- Heat flows from hot body to a colder body, this flow of heat is called transmission of heat. - Iron seems colder in winter-                                              During winter, the temperature of our body is higher than the room temperature. When we touch iron, the iron rapidly conducts heat from our hand and gives a cold feeling. Wood, on the other hand, is a bad conductor of heat, it conducts heat slowly from our hand and appears cold. - The water from a hand pump is warm in winter and cold in summer- This is because in winter the outside temperature is low and in summer outside temperature is higher as compared to the temperature of water obtained from underground water, which remains practically unchanged due to earth being bad conduct of heat. - Why we use blankets and quilts filled with cotton good in winter- Because the fibres of...

What is Echo?                   - When a person shouts in a big empty hall, we first hear his original sound, after that we hear the reflected sound of the shout. This reflected sound is known as Echo. An echo is nothing but just the reflected sound. So, the repetition of sound caused by the reflection of the sound waves is called an echo.  - The sensation of the sound persists in our brain for about 0.1s, i.e. sound to hear a distinct echo, the time interval between the original sound and the reflected sound must be 0.1s.  - The minimum distance between the source of the sound and the obstacle must be 17.2m. This distance will change with the change in temperature. Echoes may be heard more than once due to successive multiple reflections. The rolling of thunder is due to successive reflections of sound from a number of reflecting surfaces, such as clouds and the land. It is used in measuring the depth of sea and altitu...

What is Friction?                                 When a body slides or rolls over another body or on a surface, then force opposing the motion between those surface of the body which is in contact and work against the motion is called Frictional Force which will be parallel to the surface in contact.  Applications- - Friction also works between our feet and surface of walking, without friction, we can not walk at all. So, friction is necessary for us to walk and it works against our direction of motion. - This is also the reason for earthquakes when the forces causing the rocks to slide exceed the force of friction, the rock will start to move and release a great amount of energy causing the earthquake, that shake the part of the earth. -We Can not drive a car without friction between tyres and road, tyres move forward and friction works backwards lead to move the tyre in forwardin...

What is Wind Mill?               - It is a machine which works with the energy of blowing air or wind. It is the structure similar to a late electric fan that is erected at some height on a rigid support. Principle of Windmill- When the blowing air   or wind strike across the blade of a windmill, it exerts a force on them due to which blade of the windmill start rotating. This rotational motion of the blade can be used to drive a large number of machines like water pumps, flour mills and electric generator. Wind Generator- Windmill used for generating electricity is called wind Turbine and the complete setup of generating electricity by using wind energy is called a wind generator. The end rotates the blade of the wind turbine which in turn rotates the armature or coil of a small electric generator to produce electricity. [ Denmark is called the country of winds. More than 25% of their electricity needs are generated through a vast ...