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Showing posts from August, 2020

ELECTROMAGNETIC WAVES

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                 1. INTRODUCTION In this topic you will learn that how an electric current produces magnetic field and that two current- carrying wires exert a magnetic force on each other. James Clerk Maxwell (1831-1879), argued that this was indeed the case – not only an electric current but also a time- varying electric field generates magnetic field. While applying the Ampere’s circuital law to find magnetic field at a point outside a capacitor connected to a time-varying current, Maxwell noticed an inconsistency in the Ampere’s circuital law. He suggested the existence of an additional current, called by him, the displacement current to remove this inconsistency. Maxwell formulated a set of equations involving electric and magnetic fields, and their sources, the charge and current densities. These equations are known as Maxwell’s equations. Together with the Lorentz force formula, they mathematically express all the basic laws of elect...
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ALTERNATING CURRENT

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                1. INTRODUCTION The electricity which we are using at our home, offices, schools, to run many appliances such as fans, lights, projectors, computers, etc. are Alternating current (a c). The electric mains supply in our homes and offices is a voltage that varies like a sine function with time. Such a voltage is called alternating voltage (a c voltage) and the current driven by it in a circuit is called the alternating current (a c current). Today, most of the electrical devices we use require a c voltage. This is mainly because most of the electrical energy sold by power companies is transmitted and distributed as alternating current. The main reason for preferring use of a c voltage over d voltage is that a c voltages can be easily and efficiently converted from one voltage to the other by means of transformers. Further, electrical energy can also be transmitted economically over long distances. AC circuit exhibit characteristics ...
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Marathon

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                  Marathon measurements  » 1 Marathon distance = " 42.2 kilometres (km)"  = "26.2 miles"  » Half Marathon distance =0.5 Marathon =         " 21.0975 kilometres " = "13.1094 miles" » 21.1 kilometres  (13.1094 mile) is as far as: It's more than 52 laps around a track or 38 CN Towers or 231 football fields. » There are six lessons to consider before you begin you journey for half or 0.5 marathon and the full or 1 marathon: 1) Do a proper training for near about 2 years and increase you running distance every day. It is a wrong, if you are deciding to run 21.1 kilometres in the first trial. Running – smart, injury-free running – is a slow build. Choose a half marathon that's six months from now and develop a plan where you're not in a rush. It take about five weeks to get a base level of fitness – essentially where five kilometres didn't kill you. After that, you can increase you runni...
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ELECTROMAGNETIC INDUCTION

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              1. INTRODUCTION Electricity and magnetism were considered separate and unrelated phenomena for a long time. In the early decades of the nineteenth century, experiments on electric current by Oersted, Ampere and a few others established the fact that electricity and magnetism are inter-related. They found that moving electric charges produce magnetic fields. For example, an electric current deflects a magnetic compass needle placed in its vicinity. This naturally raises the questions like: Is the converse effect possible?Can moving magnets produce electric currents? Does the nature permit such a relation between electricity and magnetism? The answer is resounding yes! The experiments of Michael Faraday in England and joseph Henry in USA, conducted around 1830, demonstrated conclusively that electric currents were induced in closed coils when subjected to changing magnetic fields. In this topic, we will study the phenomena asso...
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MAGNETISM AND MATTER

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                1. INTRODUCTION This topic deals with the magnetism and the matter. Basically, there are three mainly known matter surrounding us -Solid, Liquid and Gaseous. And two more not mainly known matters - Plasma state and Bohr's Einstein Condensate. Magnetic phenomena are universal in nature. Vast, distant galaxies, the tiny invisible atoms, humans and beasts all are permeated through and through with a host of magnetic fields from a variety of sources. The earth’s magnetism predates human evolution. The word magnet is derived from the name of an island in Greece called magnesia where magnetic ore deposits were found, as early as 600 BC. Shepherds on this island complained that their wooden shoes (which had nails) at times stayed struck to the ground. Their iron-tipped rods were similarly affected. This attractive property of magnets made it difficult for them to move around. The directional property of magnets was also known since ancie...
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MOVING CHARGES AND MAGNETISM || MOVING CHARGES AND MAGNETISM Class 12 Notes || Class 12 Notes || Notes ||

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                     1. INTRODUCTION This topic deals with the moving charges and the magnetic effect. Both Electricity and Magnetism have been known for more than 2000 years. However, it was only about 200 years ago, in 1820, that it was realised that they were intimately related. During a lecture demonstration in the summer of 1820, Danish physicist Hans Christian Oersted noticed that a current in a straight wire caused a noticeable deflection in a nearby magnetic compass needle. He investigated this phenomenon. He found that the alignment of the needle is tangential to an imaginary circle which has the straight wire as its centre and has its plane perpendicular to the wire. It is noticeable when the current is large and the needle sufficiently close to the wire so that the earth’s magnetic field may be ignored. Reversing the direction of the current reverses the orientation of the needle. The deflection increases on increasing ...
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CURRENT ELECTRICITY || CURRENT ELECTRICITY Class 12 Notes || Notes ||

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            1. INTRODUCTION All the charges whether free or bound, were considered to be at rest. Charges in motion constitute an electric current. Such currents occur naturally in many situations. Lightning is one such phenomenon in which charges flow from the clouds to the earth through the atmosphere, sometimes with disastrous results. The flow of charges in lightning is not steady, but in our everyday life we see many devices where charges flow in a steady manner, like water flowing smoothly in a river. A torch and a cell-driven clock are examples of such devices.          2. ELECTRIC CURRENT Imagine a small area held normal to the direction of flow of charges. Both the positive and the negative charges may flow forward and backward across the area. In a given time interval t, let q+ be the net amount (i.e., forward minus backward) of positive charge that flows in the forward direction across the area. Similarly, let q–...
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ELECTROSTATIC POTENTIAL AND CAPACITANCE || Electrostatic Potential and CapacitenceClass 12 Notes || Notes ||

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               1. INTRODUCTION In this topic you will learn about the electrostatic potential and the capacitance. When an external force does work in taking a body from a point to another against a force like spring force or gravitational force, that work gets stored as potential energy of the body. When the external force is removed, the body moves, gaining kinetic energy and losing an equal amount of potential energy. The sum kinetic and potential energies is thus conserved. Forces of this kind are called conservative forces. Spring force and gravitational force are examples of conservative forces.  Coulomb force between two (stationary) charges is also a conservative force. This is not surprising, since both have inverse-square dependence on distance and differ mainly in the proportionality constants – the masses in the gravitational law are replaced by charges in Coulomb’s law. Thus, like the potential energy of a mass in a gravitationa...
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QUANTUM NUMBERS (Principal, Azimuthal, Magnetic and Spin)

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                  QUANTUM NUMBERS  Orbitals represent regions in the space around the nucleus where the probability of finding the electron is maximum. A large number of electron orbitals are possible in atom. These can be distinguished by their size, shape and orientation of the orbitals. To describe each electron in an atom in different orbitals, we need a set of three numbers known as quantum numbers. These are designated as n, l and m. In addition to these three numbers another quantum number is also needed which specifies the spin of the electron. These four numbers are called quantum numbers. These are discussed below: 1. Principal quantum number (n) :  This quantum number determines the main energy shell or level in which the electron is present. It is denoted by n. It can have whole number values starting from 1 such as n = 1, 2, 3, 4 ... This quantum number also identifies as shell. The shell with n 1 is called the first sh...
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Diagonal Relationship between Beryllium and Aluminium || Relation between Beryllium and Aluminium

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  Diagonal Relationship between Beryllium and Aluminium The ionic radius of Beryllium (Be 2+) is estimated to be nearly 31 pm; the charge/radius ratio Or e/m ratio is nearly the same as that of the Al 3+ ion. Hence beryllium resembles aluminium in these ways. Some of the similarities are given below: » Like Aluminium, Beryllium(be) is not readily attacked by acids H+ donor because of the formation of an oxide film on the surface of the metal by reacting with oxygen, i.e. they are rendered passive by nitric acid. » Beryllium hydroxide[[Be(OH)4]2] dissolves in excess of alkali to give a beryllate ion, [ Be(OH)4]2– just as aluminium hydroxide[Al(OH)3] gives aluminate ion, [Al(OH)4] » The chlorides of metals beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong as Lewis acids They are used as Friedel Craft catalysts. » Beryllium(Be) and aluminium(Al) ions have strong tendency to form complexes, (Be...
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Math question

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A tower, x metre, has a flagstaff at its top. The tower and flagstaff subtends equal angles at a point distant y metre from the foot of the tower. Then find the length of the flagstaff ( in metre). 
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Solar System, Planets, Moons, Asteroid Belt,Kuiper Belt and Oort Cloud, Comets and Meteoroids

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 The solar system consists of the Sun, which is a star at its center, and all the celestial bodies bound by its gravitational pull. These bodies include planets, moons, asteroids, comets, and other objects. Key Components of the Solar System: The Sun : The Sun is the center of the solar system and contains about 99.86% of its mass. It is a star primarily composed of hydrogen and helium, providing the heat and light that sustains life on Earth. Planets : There are eight recognized planets in the solar system: Mercury : The closest planet to the Sun, known for extreme temperature variations and no atmosphere. Venus : Similar in size to Earth but with a thick, toxic atmosphere and surface temperatures hot enough to melt lead. Earth : The third planet from the Sun, the only known planet to support life, with water and a breathable atmosphere. Mars : Known as the Red Planet, it has a cold, dry surface and signs of past water. Jupiter : The largest planet, a gas giant, w...
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