Knowledge of Science

                         Cell  Cell -   The cell is the fundamental unit of life. All plants and animals are made up of cells. Cell is the microcosm (having a definite boundary with in) which constant chemical activities and flow of energy proceed. Cell is the structural and functional unit of all organisms.       The body of an organism may contain one cell as in Unicellular organisms. Each cell has the capacity to perform all vital activities like nutrition, growth, respiration, irritability, movement and reproduction etc. Discovery of cell - The cell was discovered by the scientist Robert Hooke in 1665, when he worked on the wooden cork. He cut the thin slices of wooden cork and see these thin slices of cork in the self made microscope. Then he saw the honey comb like structures . These structures are called cell by the scientist Robert Hooke in 1665. **  The cell which is discovered by the scientist Robert Hooke was a dead cell.  ** The first living cell (B

Real images and virtual images  (1) Real images-   The image which can be obtained on a screen is called a real image .  In a cinema hall , we see the images of actors and actresses on the screen. So, the images on a cinema screen is an example of real images. A real image is formed when light rays coming from an object actually meet at a point after reflection from a mirror ( or refraction through a lens ). A real image can be formed on a screen because light rays actually pass through a real image. Real images can be formed by a concave mirror. A convex lens can also form real images. (2) Virtual images-  The image which cannot be obtained on a screen is called a virtual image . A virtual image can be seen only by looking into a mirror ( or a lens) . The image of our face formed by a plane mirror cannot be obtained on a screen, it can be seen only by looking into the mirror. So the image of our face in a plane mirror is an example of virtual image. Virtual images are

                    Ohm's law  Ohm's law gives a relationship between current and potential difference. According to Ohm's law -      At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its end.         If I is the current flowing through a conductor and V is the potential difference ( or voltage) across its ends,then according to Ohm's law -              I ~ V   ( At constant temperature)       or,  V~ I       or,   V =  R  ×  I Where R is a constant called       " resistance'' of the conductor.  The SI unit of resistance is ohm. The value of this constant depends on the nature, length,are a of cross - section and temperature of the conductor.                                       V          Resistance R = --------                                        I The above equation is a mathematical expression of Ohm's law.

        Apiculture ( Bee Keeping)  Bee keeping or Apiculture ( L. apis = bee, culture= cultivate ) is the rearing, care and management of honey bees for obtaining honey, wax and other substances. Honey is known to have medicinal value. It is found to be quite useful in the treatment of various disorders of human beings related to digestion, dysentery, vomiting and stomach or liver ailments.              Bee keeping being ,a low investment enterprise, has become a favourite source of some extra income for the  farmers .Bee keeping is also helps in cross pollination of flowers. Products obtained from Apiculture -  (1) Honey -   Honey is a sweet, viscous edible fluid containing sugars , water, minerals, vitamins, amino acids, enzymes and pollen. Sugars present in honey include levulose , dextrose, sucrose and dextrin. Minerals of honey are calcium, iron, phosphate and manganese. The colour,flav fla and odour of honey usually depends on the flowers from which nectar is gathered.

                       Acids * Acids are those compounds    which gives Hydrogen ions (H+ ion) in aqueous solutions. For example-        HCl --------> H+    +  Cl`        (aq)            (aq)       (aq) * Acids are those compounds which makes hydronium ions in aqueous solutions. For example-           HCl --------> H+    +  Cl`        (aq)            (aq)       (aq) H+  +   H2O ------->  H3O+                            (Hydronium ion) * Acids are those compounds which is reacts with bases and form salts and water. For example- NaOH  +  HCl -------> NaCl +H2O (Base)     (Acid)      (Salt)   (Water) * Acids are those compounds which are bitter in taste.    For example- citric acid , lactic acid etc. *Organic acids and mineral acids- (1) Organic acids-   The acids present in plant materials and animals are called organic acids.  For example- Acetic acid, formic acid etc. (2)Ino rganic acids-   The acids prepared from the

                  Force  When we want to open a door, we have to push the door handle. And when we want to close the door, we have to pull the door handle with our hands. This means that to move a body or an object, it has either to be pushed or pulled.           A push or pull on a body is called force. The direction in which a body is pushed or pulled is called the direction of force.         Forces are used in our everyday actions like pushing, pulling, lifting, stretching, twisting and pressing. For example - A force is used when we push (kick) a football.   Effects of force -       A force cannot be seen. A force can be judged only by the effects which it can produce in various bodies or objects around us . A force can produce the following effects -  1) A force can move a stationary body. 2) A force can stop a moving body. 3) A force can change the speed of a moving body. 4) A force can change the direction of a moving body. 5) A force can change the sha

        Dalton's atomic theory  The theory that all matters is made up of very tiny indivisible particles (atoms) is called atomic theory of matter. Dalton put forward his atomic theory of matter in 1808.       The various postulates or assumptions of Dalton's atomic theory of matter are as follows- (1) All the matter is made up of very tiny particles called atoms. (2) Atoms cannot be divided. (3) Atoms can neither be created nor be destroyed. (4) Atoms are of various kinds. There are as many kinds of atoms as are elements. (5) All the atoms of a given element are identical in every respect, having the same mass, size and chemical properties. (6) Atoms of different elements differ in mass, size and chemical properties. (7) Chemical combination between two or more elements consists in the joining together of atoms of these elements to form molecules of compounds. (8) The numbers and kind of atoms in a given compound is fixed. (9) During chemical combina

               The Gas law  (A) Boyle's law -  This law is given by the scientist Robert Boyle in 1662. According to this law-   The volume of a given mass of a gas is inversely proportional to its pressure provided the temperature remains constant.                                                                                 1  v     =   -----            ( at constant                     p          temperature )  Or,     pv =  k = constant Let the pressure and volume of any  gas is p   and V  and the                        1           1   pressure and volume    of the same  amount of the same gas be p  and v      then -  2           2     p   v    =   p    v  = constant       1    1         2    2  (B) Charles' law-    This law is given by the scientist J. Charles in 1787. According to this law- At constant pressure, the volume of a given mass of a gas is directly proportional to its absolute temperature.      V   ~  T  (at

Laws of chemical combination (1)Laws of conservation of mass-  This law is given by the French scientist A. Lavosier in 1774.            According to this law- In any physical or chemical change the total mass of the products is always equal to the total mass of the reactants. This law is also represents as - Matter is neither be created nor be destroyed in any physical or chemical change but it transformed into one form to another form.     For example-    2H2O  ------> 2H2  + O2   36 gram      4 gram   32 gram (2)Law of constant proportion- This law is given by the French scientist Proust in 1799.            According to this law- In any chemical compound , the elements presents in the compound are always present in a fixed proportion by mass.    For example- (a)In the compound CO2 the ratio of Carbon and Oxygen is always found in the 3:8 by mass. (b)  In the compound H2O the ratio of Hydrogen and Oxygen is always found in the 1:8 by mas

वांट हॉफ कारक(van't Hoff factor ) वांट हॉफ (1886) ने विलेय पदार्थो के आणविक संयोजन तथा वियोजन का विस्तृत अध्ध्यन किया तथा विलेय पदार्थ के विलयन में संयोजन या वियोजन की सीमा को व्यक्त करने के लिए एक कारक i की कल्पना की | इस कारक को वांट हॉफ कारक कहते हैं | इसे निम्न प्रकार परिभाषित किया जा सकता है - किसी अणुसंख्य गुणधर्म के प्रायोगिक मान (observed value ) तथा सामान्य मान (calculated value ) के अनुपात को वांट हॉफ कारक i कहा जाता है | गणितीय रूप में,      किसी अणुसंख्य गुणधर्म का प्रायोगिक                       मान (observed value ) i =  --------------------------------------------       किसी अणुसंख्य गुणधर्म का  सामान्य             मान (calculated value )                         ∆                           obs  या,        i =    ------------                         ∆                           cal वाष्प दाब में अवनमन के लिए,                    (∆p)                           obs           i =    ------------                    ( ∆p)                            

  उत्प्रेरण (Catalysis )  रासायनिक अभिक्रियाओं की गति किसी विशिष्ठ पदार्थ की थोड़ी सी मात्रा की उपश्थिति से प्रभावित हो सकती है | इस प्रकार के पदार्थो को उत्प्रेरक कहा जाता है तथा इस घटना को उत्प्रेरण कहते हैं | उत्प्रेरण पद को सर्वप्रथम बर्जीलियस ने सन 1836 में प्रयोग किया था | (A) धनात्मक उत्प्रेरण ( positive catalysis )-  वे उत्प्रेरक जो अभिक्रिया के वेग को बढ़ा देते हैं उन्हें धनात्मक उत्प्रेरक कहा जाता है तथा इस घटना को धनात्मक उत्प्रेरण कहते हैं | जैसे -                        Pt         2H2O2 --------> 2H2O + O2 (B) ऋणात्मक उ त्प्रेरण ( Negative  catalysis )-  वे उत्प्रेरक जो अभिक्रिया के वेग को घटा  देते हैं उन्हें ऋणात्मक उत्प्रेरक कहा जाता है तथा इस घटना को ऋणात्मक उत्प्रेरण कहते हैं | जैसे - टेट्रा एथिल लेड (TEL ) की उपश्तिथि द्वारा पेट्रोल का अपस्फोटन कम हो जाता है |       उत्प्रेरण के प्रकार ( Types of Catalysis ) (1) समांग उत्प्रेरण (Homogeneous catalysis )--    जब उत्प्रेरक व अभिकारक एक ही प्रावस्था में स्थित होते हैं तथा अभिक्रिया तंत्र पूर

फैराडे के विद्युत् अपघटन के नियम (Faraday's laws of electrolysis) माइकल फैराडे ने सन 1832 में  विद्युत् अपघटन का गहन अध्ययन किया और इलेक्ट्रोडो पर मुक्त उत्पादों की मात्रा व प्रवाहित विद्युत् धारा की मात्रा के बीच सम्बन्ध के लिए दो नियम दिए | इन्हे फैराडे के विद्युत् अपघटन के नियम कहते हैं | ये नियम निम्न हैं - (1) फैराडे का  विद्युत् अपघटन का प्रथम नियम -  विद्युत् अपघटन की प्रक्रिया में किसी इलेक्ट्रोड विशेष पर मुक्त या एकत्रित पदार्थ का द्रव्यमान विलयन में प्रवाहित की गयी विद्युत् धारा की मात्रा ( कुल आवेश ) के समानुपाती होता है |   यदि विलयन में विद्युत् (आवेश ) के Q कूलम्ब को प्रवाहित करने पर किसी इलेक्ट्रोड पर एक पदार्थ के W ग्राम मुक्त होते हैं , तो फैराडे के   विद्युत् अपघटन के  प्रथम नियम के अनुसार ,          आवेश = विद्युत् धारा × समय या ,       Q = I × t या ,        W = Z × I × t जहाँ Z एक स्थिरांक है , जिसे विद्युत् रासायनिक तुल्यांक कहते हैं | (2) फैराडे का  विद्युत् अपघटन का द्वितीय  नियम -   जब श्रेणीक्रम में जुड़े विभिन्न विद्युत् अपघट्यो के

अणुसंख्य गुणधर्म (Colligative properties ) विलयनों के वे गुण जो विलायक की एक निश्चित मात्रा में उपश्थित विलेय कणो की संख्या पर निर्भर करते हैं किन्तु विलेय की रासायनिक प्रकृति पर निर्भर नहीं करते हैं, अणुसंख्य गुणधर्म कहलाते  हैं |            विलयनों के महत्वपूर्ण  अणुसंख्य गुणधर्म निम्न हैं - (1) वाष्पदाब में सापेक्ष अवनमन  (2) क्वथनांक में उन्नयन  (3) हिमांक में अवनमन  (4) परासरण दाब      (1) वाष्पदाब में सापेक्ष अवनमन -  किसी वाष्पशील विलायक में एक अवाष्पशील विलेय को मिलाने पर उसके वाष्पदाब में कमी उत्पन्न होती है | यदि किसी शुद्ध विलायक का वाष्पदाब p° तथा विलयन का वाष्पदाब p हो तो         वाष्पदाब में अवनमन =p° - p तथा  वाष्पदाब में सापेक्ष अवनमन = p° - p                                                  --------                                                    p° राउलट के नियम के अनुसार , p° - p  --------- = x (विलेय )     p°  (2) क्वथनांक में उन्नयन -   किसी विलेय पदार्थ को किसी विलायक में मिलाने पर उस विलायक के क्वथनांक में वृद्धि हो जाती है , इसे

Some important model of Atom   (कुछ महत्वपूर्ण परमाणु मॉडल ) (A) टॉमसन का परमाणु मॉडल -  जे. जे. टॉमसन ने 1904 में परमाणु का प्रथम मॉडल दिया | इसे टॉमसन का तरबूज मॉडल भी कहते हैं | इसके अनुसार परमाणु इलेक्ट्रोनो तथा धन आवेशित द्रव्य से मिलकर बना है | परमाणु गोलाकार  अति सुक्ष्म तथा विद्युत् उदासीन कण है |परमाणु में धन आवेशित द्रव्य समान रूप से फैला हुआ है तथा इलेक्ट्रान धन आवेशित द्रव्य में इस प्रकार धँसे हुए हैं जैसे तरबूज में बीज धँसे रहते हैं | (B) रदरफोर्ड का परमाणु मॉडल -  अर्नेस्ट रदरफोर्ड ने  अल्फ़ा - कणों के प्रयोग से नाभिकीय मॉडल दिया | इस मॉडल के अनुसार - 1) परमाणु गोलाकार, अति सूक्ष्म तथा विद्युत् उदासीन कण है | 2)परमाणु का समस्त धनावेश तथा लगभग समस्त द्रव्यमान उसके केंद्र में एक सूक्ष्म आयतन में संचित रहता है | 3)परमाणु में इलेक्ट्रान तथा प्रोटोन होते हैं |परमाणु में  प्रोटोन उसके नाभिक में तथा इलेक्ट्रान  नाभिक के बाहर होते हैं | 4)परमाणु में इलेक्ट्रान नाभिक के चारो ओर जिन पथो पर घूमते हैं, उन्हें इलेक्ट्रोनो की कक्षाएं कहते हैं |इलेक्ट्रान नाभिक के चार

  Redox reactions     The word redox is made up by the two words (red+ ox) . Red means reduction and ox means oxidation. So, the redox reaction is the type of reaction in which reduction and oxidation both are takes place. Example- Zn  + cuSo4 = ZnSo4  + Cu (1) Oxidation reaction -  The reaction in which the electron are loss by the atom, molecules or ions is known as the oxidation reaction. Example- Na = Na+   +  e-                   OR Oxidation is the process in which oxygen is added in the atoms, molecules or ions is known as the oxidation reaction. 2Mg + O2  = 2MgO (2) Reduction reaction- The reaction in which the electron are gain by the atom, molecules or ions is known as the oxidation reaction. Example- Cu + e- = Cu-                OR Reduction is the process in which oxygen is removed by the atoms, molecules or ions is known as the reduction reaction. Example- 2H2O = 2H2 + O2

        Types of fungi  On the basis of the nutrition the fungi are classified into several groups. These are- 1)Parasite- These fungus are obtained their food from any living beings or from any living tissues. If fungi obtain their food from the outer surface of the living (host) then it is called the ectoparasites and if they obtain their food from the inner side of the living then it is called as the endoparasite. Parasites are of two types- a)Obligate parasites- These fungus are obtained their food from the only living host. example- Puccinia b) Facultative saprophytes - These parasites obtained their food from dead and decaying matters in the absence of living beings as a saprophytes. example- Mucor 2) Saprophytes- These fungus are obtained their food from the dead and decaying matters. They are two kinds- a) Obligate saprophytes- These fungus are obtained their food from only dead organic matter. Example- Mucor b) Facultative parasites- These saprop

Head and mouth parts of Anopheles female mosquito 1) It transmits malarial disease and acts as intermediate host for plasmodium. 2) Mouth parts are piercing and sucking type, composed of labrum-epipharynx,needle shaped mandibles and maxillae , Hypopharynx,maxi maxillary palps and labium. 3) Maxillary palps are simple and equal to labium or proboscis. 4) Antennae possess a few short hairs at joints. 5)Head is freely movable on a delicate and slender neck,having large black compound eyes and antennae. 6) Clypeus articulates with Labrum and epipharynx.

Head and mouthparts of Housefly(Musca domestica) 1) Housefly belongs to order Diptera and contains sponging mouth parts, adapted for sucking liquid food. 2) These insects lack the cutting apparatus. 3) Head, besides ocelli and antennae, bears mouth parts. Antennae are aristate. 4) Mouth parts are composed of proboscis, short maxillary palps,labrum- epipharynx and hypopharynx. Mandibles are absent. 5) Maxillae are represented by short and unjointed maxillary palps before the rostrum. 6) Labrum is fused with the epipharynx and forms a narrow slender tube opening ventrally. 7) Hypopharynx is narrow structure. Containing salivary duct and fits into the tube constituted by labrum- epipharynx. 8) Proboscis is retractile,fleshy and differentiated into basal rostrum, middle haustellum and upper labellum. Labellum contains pseudo-tracheal ,canals,bounded by pseudo-tracheal membrane. Labium forms a tube and encloses labrum-epipharynx and hypopharynx. 9) Hypopharynx and la