# Current Affairs UPSC

#### Measurements and Motion

MEASUREMENTS AND MOTION     MEASUREMENTS   The process of comparing an unknown physical quantity with respect to a known quantity is known as measurement. When we say that the length of our bedroom is 10 feet it implies that the bedroom is 10 times the known quantity ?foot? (feet is the plural of foot). So, measurement of any physical quantity consists of two parts - (i) a numerical value and (ii) the known quantity. The known quantity is called the unit of that physical quantity. Measurement is an integral part of physics. Physics is the foundation on which engineering, technology and other sciences are based.   PHYSICAL QUANTITIES Quantities which can be measured are called physical quantities. Velocity, acceleration, force, area, volume, pressure, etc. are some examples of physical quantities.   Kinds of Physical Quantities There are two kinds of physical quantities   Fundamental physical quantities: Fundamental physical quantities are those which do not depend on other quantities and also independent of each other. They are seven in number viz; length, mass, time, thermodynamic temperature, electric current, luminous intensity and amount of substance.   Derived physical quantities: Derived physical quantities are those which are derived from fundamental physical quantities. For example, velocity is derived from the fundamental quantities length and time, hence it is a derived physical quantity.   UNITS To measure a physical quantity it is compared with a standard quantity. This standard quantity is called the unit of that quantity. For example, to measure the length of a desk, it is compared with the standard quantity known as ?metre?. Thus, ?metre? is said to be the unit of length.   Types of Units There are two types of units:   Fundamental units: Fundamental units are those units more...

#### Non - Metal

NON - METALS   Non-metals occupy the upper right hand comer of the periodic table. Seventeen elements are generally classified as non-metals. Their names as per their states in the normal conditions are: Gases: hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon. Liquid: bromine. Solid: carbon, phosphorus, sulphur, selenium, and iodine.   PROPERTIES OF NON-METALS Physical Properties
• Non-metals are neither malleable nor ductile.
• They are brittle (break easily).
• They do not conduct heat and electricity.
• They are not lustrous (not shiny). They are dull.
• They are generally soft (except diamond which is extremely hard non-metal).
• They may be solid, liquid or gases at the room temperature.
• They have comparatively low melting points and boiling points (except diamond which is a non-metal having a high melting point and boiling point).
• Non-metals have low densities, that is, non-metals are light substances.
• Non-metals are non-'sonorous. They do not produce sound when hit with an object.
Chemical Properties of Non-Metals Non-metals are more reactive with metals than with other non-metals. Generally non-metals react with each other at a high temperature.   Action of Air: Non-metals do not react with air at room temperature except white phosphorus.   Action of water: Generally, non-metals do not react with water. However, chlorine dissolves in water and form an acidic solution.   Displacement of one non-metal by another from salt solution: Just like metals, non-metals also differ in their reactivity’s. Among halogen family (i.e. Cl, Br, I and F) the most reactive is chlorine (Cl). The order of reactivity is Cl > Br > I. Thus chlorine can displace Br and I from solutions of bromides (NaBr) and Iodides (Nal).   Reaction with metals: Non-metals with high electronegativity (F, Cl, Br etc.) generally reacts with alkali and alkaline earth metals to form ionic compounds.   Handy Facts Allotropes are different from of the same element. Different bonding arrangements between atoms result in different structures with different chemical and physical properties. For example: The all tropes forms of carbon are white, red and black phosphorous. The term allotropy is referred to element only another term polymorphism is used to mean the ability of solid to exist in more than one term or crystal structure.   SOME IMPORTANT NON-METALLIC ELEMENTS Hydrogen The discovery of hydrogen is credited to Henry Cavendish in 1766, although it had been isolated as early as 1671 by Robert Boyle.   Isotopes of Hydrogen Three isotopes of hydrogen exist and all occur naturally.
• $^{\text{1}}\text{H}$is sometimes called Protium, It is abundent in nature. It is the only hydrogen isotope lacking neutrons.
• The second isotope, $^{2}\text{H}$, is called deuterium
Handy Facts D-element bonds are more difficult to break than H-element bonds and this fact allows the mechanisms or many chemical reactions to be examined. ${{D}_{2}}O$itself is important as a material that slows neutrons in nuclear reactors.
• The third isotope,$^{3}\text{H}$, Tritium is radioactive.
• more...

#### Laws of Motion, Force, Work, Energy & Power, Centre of Mass

LAWS OF MOTION, FORCE, WORK, ENERGY & POWER, CENTRE OF MASS     LAWS OF MOTION AND FORCE   Everybody in this universe stays in a state of rest i.e., no change in position of a body wrt time or of uniform motion i.e., change in position of a body wrt time. This chapter is concerned about the cause of rest or motion (i.e., force) and its effect (i.e., acceleration or deceleration) and their relationship.   NEWTON'S LAWS OF MOTION Newton’s First Law of Motion According to this law, an object continues in a state of rest or in ci state of motion at a constant speed along a straight line, unless compelled to change that state by a net force. In other words, if ci body is in a state of rest, it will remain in the state of rest and if it is in the state of motion, it will remain moving in the same direction with the same velocity unless an external unbalanced force is applied on it. This law is also called law of inertia. It gives qualitative definition of force.   Handy Facts A common misconception about Newton’s first law of motion is that a force is required to keep an object in motion. This is not so. Experiments done on air tracks (where there is a negligible friction) show that no force is required to keep an object moving with constant velocity. We get this misconception because friction is always present in our everyday lives.   Inertia and Mass A greater net force is required to change the velocity of some objects than of others. The net force that is just enough to cause a bicycle to pick up speed will cause an imperceptible change in the motion of a freight train. In comparison to the bicycle, the train has a much greater tendency to remain at rest. Accordingly, we say that the train has more inertia than the bicycle. Quantitatively, the inertia of an object is measured by its mass. Inertia is the natural tendency of an object to remain at rest or in motion at a constant speed along a straight line. The mass of an object is a quantitative measure of inertia. The greater the mass, the greater is the inertia of body.   Types of Inertia Inertia of rest: The tendency of the body to continue in state of rest even when some external unbalanced force is applied on it is called inertia of rest.   Science in Action
• When a carpet is suddenly jerked the dust fly off, because due to the sudden jerk the carpet moves but the dust on account of inertia of rest is left behind.
• The passenger standing in a bus tends to more...

#### Atoms, Molecules and Nuclear Chemistry

ATOMS, MOLECULES AND NUCLEAR CHEMISTRY     ATOMS AND MOLECULES   The combination of different elements to form compounds is governed by some basic rules. These rules, collectively called ‘laws of chemical combination’.   LAW OF CHEMICAL COMBINATIONS Law of Conservation Mass: Lavoisier, who is widely regarded as the father of modem chemistry gave the law of conservation of mass. This law states that in any chemical reaction, the mass of the substances that react equals the mass of the products that are formed.   Law of Definite Proportions: This Jaw was given by Joseph Proust, a French chemist, in 1799. Proust’s law of definite proportions states that different samples of the same compound always contain its constituent elements in the same proportion by mass.   Law of Multiple Proportions: In 1803 Dalton gave this law. As per this law if two elements combine to form more compounds, the masses of one element combine with a fixed mass of the other element, are in the ratio of small whole numbers.   The Law of Gaseous Volume: When gases react, the volumes consumed and produced, measured at the same temperature and pressure, are in ratios of small whole numbers. This is also known as Gay-Lussac’s Law.   Dalton’s Atomic Theory The hypotheses about the nature of matter on which Dalton’s atomic theory is based can be summarized as:
• Matter consists of indivisible atoms.
• All the atoms of a given chemical element are identical in mass and in all other properties.
• Different chemical elements have different kinds of atoms and in particular such atoms have different masses.
• Atoms are indestructible and retain their identity in chemical reactions.
Laws of Chemical Combination and Dalton’s Theory
• Dalton’s fourth postulate explains the law of conservation of mass.
• The fifth postulate is an attempt to explain the law of definite proportions.
ATOMS Atoms are building blocks of all matter. On the basis of Dalton’s atomic theory, we can define an atom as the basic unit of an element that can enter into chemical combination. The size of an atom is extremely small and not visible to eye. The comparative idea regarding the size of atom can be had from the following:   more...

#### Evolution and Ecological Biodiversity

EVOLUTION AND ECOLOGICAL BIODIVERSITY     EVOLUTION     The branch of life science for the study of ‘origin of life’ and evolution of different forms of life on earth was called bio evolution or evolutionary biology by Mayer, (1970). The word evolution means to unfold or unroll or to reveal hidden potentialities. Evolution simply means an orderly change from one condition to another. Evolution is slow but continuous process which never stop.   ORIGIN OF LIFE
• Origin of life is the process by which living organisms developed from inanimate matter which is generally thought to have occurred on Earth between 3800 – 4200 millions years ago. First life evolved 3800-4200 million years back. There are several theories about the origin of life, like big bang theory, theory of special creation, theory of eternity, cosmozoic theory etc.
Chemosynthetic Theory of Origin of Life The widely accepted theory is the Chemosynthetic theory of origin of life proposed by A.I. Oparin. It states that life has originated on earth through a series of combinations of chemical substances in the distant past. All these processes took place in water.
• The early atmosphere contained ammonia ($N{{H}_{3}}$), water vapour (${{H}_{2}}O$), hydrogen (${{H}_{2}}$), methane
($C{{H}_{4}}$). At that time there was no free oxygen.   Miller and Urey Experiment           CHEMICAL EVOLUTION AND ORGANIC EVOLUTION         Comparative Anatomy and Morphology
• Different animals and plants show dissimilarities in their structure but in some characters they show similarity. These similarities provide one of the most concluding evidence of organic evolution.
• Similarities are of two types: homology and
Let us discuss some of the important sources that provide evidences/or evolution.
• Homologous organs: Homologous organs are similar in origin (or are embryo logically similar) but perform different functions.
For example, the forelimbs of humans and the wings of birds look different externally but their skeletal structure is similar.   ·
• Analogous organs: Analogous organs have different origin but perform similar functions.
For example, the wings of a bird and a bat are similar in function but this similarity does not mean that these animals are more closely related.   Vestigial organs
• The organs which are present in reduced form and do not perform any function in the body but correspond to the fully developed functional organs of related animals are called vestigial organs.
• Human body possess about 180 vestigial organs. Some of these are - nictating membrane, muscles of pinna (auricular muscles), vermiform more...

#### Force of Gravity, Solids & Fluids

FORCE OF GRAVITY, SOLIDS & FLUIDS     FORCE PF GRAVITY     Earth attracts everybody towards itself with a force known as ‘gravity’. Due to the force of gravity the ball thrown upwards doesn’t go upwards but it falls downwards after covering some vertical distance. Actually, every object attracts every other object towards itself with a force. This force is called the gravitational force. Gravitational force is one among the four fundamental forces. It is always attractive in nature.   NEWTON'S UNIVERSAL LAW OF GRAVITATION   Newton came to the conclusion that any two objects in the Universe exert gravitational attraction on each other. Any two particles of matter anywhere in the universe attract each oilier with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them, i.e., $F\propto \frac{{{m}_{1}}{{m}_{2}}}{{{r}^{2}}}$     or      $F=\frac{G{{m}_{1}}{{m}_{2}}}{{{r}^{2}}}$ Here, the constant of proportionality G is known as the universal gravitational constant. It is termed a “universal constant” because it is thought to be the same at all places and all times. $G=6.673\times {{10}^{-11}}N{{m}^{2}}/k{{g}^{2}}.$   Handy Facts The value of universal gravitational constant, G is very small hence gravitational force is very small, unless one (or both) of the masses is huge.   Important Characteristics of Gravitational Force
• Gravitational forces are always attractive and always acts along the line joining the two masses.
• Gravitational force is a mutual force hence it is action-reaction force, i.e., ${{\vec{F}}_{12}}=-{{\vec{F}}_{21}}$.
• Value of G is small, therefore, gravitational force is weaker than electrostatic and nuclear forces.
• Gravitational force is a central force because $F\propto \frac{1}{{{r}^{2}}}$
• The gravitational force between two masses is independent of the presence of other objects and medium between the two masses.
Importance of the Universal Law of Gravitation The universal law of gravitation successfully explained several
• the force that binds us to the earth
• the motion of the moon around the earth
• the motion of planets around the Sun and
• the tides due to the moon and the Sun.
MASS AND WEIGHT The quantity of matter in a body is known as the mass of the body. Mass is quantitative measure of inertia. Mass is an intrinsic property of matter and does not change as an object is moved from one location to another. Weight, in contrast, is the gravitational force that the earth exerts on the object and can vary, depending on how far the object is above the earth’s surface or whether it is located near another body such as the moon. The relation between weight W and mass m $E=\frac{G{{M}_{E}}m}{{{r}^{2}}};\,\,\,\,\,\,\,\,\,\,\,\,\,W=mg$ As         ${{g}_{moon}}=\frac{1}{6}{{g}_{earth}}$ therefore,             ${{w}_{moon}}=\frac{1}{6}{{w}_{earth}}$ Inertial and Gravitational Mass The mass more...

#### Sound, Oscillations Heat & Thermodynamics

SOUND, OSCILLATIONS HEAT & THERMODYNAMICS     Sound is a form of energy that we hear. A vibrating object i.e., anything  that  moves  back  and  forth, to-and-fro from side to side, in and out and up and down produces sound, as the object (vibrating) has a certain amount of energy. Sound requires material medium-a solid, a liquid or a gas to travel. If there is no medium to vibrate then no sound is possible, sound cannot travel in a vacuum. Air is a poor conductor of sound compared with solids and liquids.   WAVE Due to the vibratory motion of the particles of the medium a periodic disturbance is produced in a material medium. This is called a wave. In the absence of medium solid, liquid or gas sound wave is not being propagated but light (electromagnetic) waves travel through the vacuum.   Types of Waves On the basis of the requirement of medium, waves are of two types   Mechanical Waves A mechanical wave is a periodic disturbance which requires a material medium for its propagation. The properties of these waves depend on the medium so they are known as elastic waves, such as sound-waves, water waves, waves in stretched string etc. On the basis of motion of particles the mechanical waves are classified into two parts. Transverse wave: When the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave, the wave is known as the transverse wave. For example, waves produced in a stretched string, waves on the surface liquid. These waves travel in the form of crests and troughs. These waves can travel in solids and liquids only. Longitudinal wave: When the particles of the medium vibrate along the direction of propagation of the wave then the wave is known as the longitudinal wave. For example sound wave in air, waves in a solid rod produced by scribing etc. These waves travel in the form of compressions and rarefactions. These waves can travel in solids, liquids and gases.   Electromagnetic Waves The waves which do not require medium for their propagation are called electromagnetic waves. This means that these waves can travel through vacuum also. For example, light waves, X-rays, y-rays, infrared waves, radio waves, microwaves, etc. These waves are transverse in nature.   Difference between sound waves and electromagnetic waves
• Sound waves are longitudinal whereas electromagnetic waves are transverse.
• Sound waves travel at a speed of 340/ m/s whereas electromagnetic waves travel at a speed of3xl08 m/s
• Sound waves do not pass through a vacuum but electromagnetic waves (light) do.
Basic Terms Related to Sound Waves Time Period (T): Time taken in one complete vibration (full cycle) is called it's time period. Frequency (v): Frequency is defined as the number of vibrations (or oscillations) completed by a particle more...

#### Elements Classification and Chemical Bonding

ELEMENTS CLASSIFICATION AND CHEMICAL BONDING     CLASSIFICATION OF ELEMENTS   Four major attempts made for classification of the elements are follows:
• Newlands’ Law of Octaves
• Mendeleev’s Periodic Law & Periodic Tables
• Modern Periodic Table
Dobereiner’s Triads In 1829, J.W. Dobereiner, a German chemist made groups of three dements each and called them triads.
• All three elements of a triad were similar in their physical and chemical properties. He proposed a law known as Dobereiner’s law of triads,
• According to this law, when elements are arranged in order of increasing atomic mass, the atomic mass of the middle element was nearly equal to the arithmetic mean of the other two and its properties were intermediate between those of the other two.
Newlands’ Law of Octaves John Alexander Reina Newlands in 1863-64 noted that every eighth element showed similar physical and chemical properties, when the elements are placed in the increasing order of their atomic masses. This was called the Newlands law of octaves.   The law states that when elements are placed in the increasing order of atomic masses, the properties of the eighth elements are repeated.   Mendeleev’s Periodic Law and Periodic Table On arranging the elements in the increasing order of atomic masses, it was observed that the elements with similar properties repeat periodically. In 1869, Mendeleev stated his observation in the form of the following statement winch is known as the Mendeleev’s Periodic Law The chemical and physical properties of elements are periodic function of their atomic masses. Mendeleev arranged the elements in the form of a table which is known as the Mendeleev’s Periodic Table as below:
• Elements were arranged in increasing order of their atomic masses in horizontal rows till element whose properties were similar to those of the first element was came across.
Salient Features of Mendeleev’s Periodic Table The following are the main features of this periodic table:
• The elements are arranged in rows and columns in the periodic table.
• The horizontal rows are called periods. There are six periods in the periodic table. These are numbered from 1 to 6 (Arabic numerals). Each one of the 4th, 5th and 6th periods have two series of elements.
• All the elements present in a particular group are chemically similar in nature. They also show a regular gradation in their physical and chemical properties from top to bottom.
Modern Periodic Law and Periodic Table The Modern Periodic Law states that the chemical and physical properties of elements are periodic functions of their atomic numbers, i.e. if elements are arranged in the order of their increasing atomic number, the elements with similar properties are repeated more...

#### Electricity, Magnetism and Light

ELECTRICITY, MAGNETISM AND LIGHT     ELECTRICITY, MAGNETISM     Electricity is the branch of physics in which we study electric charges, at rest (electrostatics or static electricity) and in motion (current electricity). When we switch on the bulb of our rooms, it glows immediately. An electric signal in a conductor travels at a speed of light in vacuum. An electric current flowing in a conductor produces a magnetic field or magnetism around it.   ELECTRIC CHARGES Charge is something associated with matter due to which it produces and experiences electric and magnetic effects. Every atom contains two types of charged particles: (i) Positive charge (Proton) and (ii) Negative charge (electron) The magnitude of elementary positive or negative charge is same and is equal to$1.6\times {{10}^{-19}}C$. Charge is a scalar quantity and its SI unit is ampere second or coulomb (C).   Basic Properties of Electric Charge (i) Similar charges repel and opposite charges attract. (ii) Charge is conserved i.e., the charge can neither be created nor be destroyed but it may simple be transferred from one body to other. Charge is transferable.   CONDUCTORS AND INSULATORS The materials which allow electric charge (or electricity) to flow freely through them are called conductors.   The materials which do not allow electric charge to flow through them are called non-conductors or insulators.   Examples of good conductors are metals, impure water etc. Examples of insulators are quartz, glass, air, rubber, etc. Silver is the best conductors of electricity.   CLOUD FORMATION, THUNDERING AND LIGHTNING Clouds are very small droplets of water in the form of vapour. Clouds roam about in the sky with the wind. Generally, a patch of cloud develops an electric charge on it by friction. As a result of friction the upper layers of cloud (which are away from earth) get positively charged and the lower layers of cloud (which are facing earth) get negatively charged. Dry and pure water are bad conductors of electricity, hence clouds continue to carry the charge on them till the intensity of charge between the two gets too high. When two patches of cloud bearing different charges cone face to face they get attracted to one another and the electrons from negatively charged cloud jump to the positively charged cloud. The jumping of electrons between the clouds results in a big spark. The heat from the spark results in sudden expansion of air setting the air in violent waves which are heard by us as thunder. The spark is seen as a flash of lightning first and then followed by a thunder, a little later. To protect tall buildings from damage by lightning, a lightning conductor is fixed on them.   COULOMB’S LAW more...

#### Genetics and Biotechnology

GENETICS AND BIOTECHNOLOGY     GENETICS   Heredity is the transmission of genetic characters from parent to off springs. Individuals of same species have some differences, these are called variation.   MENDEL’S FINDINGS
• Mendel’s Law of Dominance and Recessive
• Each of the ${{f}_{1}}$ generation plant shows inheritance of Y allele from one parent and a G allele from the other. When the ${{f}_{1}}$ plants breed, each has equal chance of passing on either Y or G allele to each offspring.
In all the seven traits that Mendel examined, one form appeared dominant over the other i.e., it marked the presence of the other allele, e.g.
 Relative sizes Radius (in meter) Example ${{10}^{-10}}$ Atoms of hydrogen ${{10}^{-4}}$ Grain of sand ${{10}^{-1}}$ Water melon $0.2\times {{10}^{-1}}$
 BASIC TERMS USED IN INHERITANCE STUDIES ·   Allele: It is an alternative form of a gene which are located on same position (loci) on the homologous chromosome. Term allele was coined by Bateson. ·   Homozygous: A zygote is formed by fusion of two gametes having identical factors is called homozygote and organism developed from this zygote is called homozygous. Ex. TT, RR, tt. ·   Heterozygous: A zygote is formed by fusion of two different types of gamete carrying different factors is called heterozygote (Tt, Rr) and individual developed from such zygote is called heterozygous. ·   Hemizygous: If individual contains only one gene of a pair then individual is said to be hemizygous. Male individual is always hemizygous for sex linked gene. ·   Phenotype: It is the external and morphological appearances of an organism for a particular character. ·   Genotype: It is the genetic constitution or genetic make-up of an organism for a particular character. ·   Back cross: A back cross is a cross in which ${{F}_{1}}$individuals are crossed with any of their parents. ·   Test cross: When ${{F}_{1}}$ progeny is crossed with recessive parent then it is called test cross. ·   Monohybrid test cross: The progeny obtained from the monohybrid test cross are in equal proportion, means 50% is dominant phenotypes and 50% is recessive phenotypes. It can be represented in symbolic forms as follows. ${{F}_{1}}$progeny (hybrid) $\times$ Recessive parent   Monohybrid test cross ratio =1:1 ·   Dihybrid test cross: The progeny is obtained from dihybrid test cross are of four types and each of them is 25%.

• Law of Segregation: According to this law, for any particular trait, the pair of alleles of each parent separate and only one allele passes from each parent to an off spring. Allele in a parent’s pair of allele is inherited as a matter of chance (we now know segregation of alleles occurs during the process of meiosis).
• Law of Independent Assortment: This is also known as ‘Inheritance law’. According to this law, different pairs of alleles are passed to offspring independently of each more...

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