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 Science Important Topics:- ☺Sexually transmitted diseases(STDs) 1. Bacterial infections: (a) GONORRHOEA                                       (b) SYPHILIS 2. Viral infections: (a) AIDS- Acquired Immuno Deficiency Syndrome                                (b) GENITAL WARTS ☺Fertilisation and post fertilisation changes        The fusion of nucleus of the sperm and ovum is known as fertilisation. This process in human takes place in the following ways: 1. The male gamete enters into the female genital tract by the process of copulation or mating. 2. Fertilisation takes place in the oviduct or Fallopian tube. 3. Fertilisation only occurs, if egg is present in the oviduct. 4. When male and female gametes fuse to each other it will form Zygote. 5. The zygote undergoes various mitotic division to form an embryo. 6. The embryo sinks down and reaches into the soft and thick lining of the uterus. 7. The embedding of the embryo in the thick lining of the uterus in known as implantation. 8. After d

 Last Important Revision@CBSE TOPPER 1. Why leaves become yellow in the absence of light? Ans:   Presence of light is quite necessary for plants because in presence of light plants by the  process of photosynthesis synthesizes their food.  In the absence of light the process of photosynthesis is not possible. For synthesis of food presence of a pigment called chlorophyll is also necessary which absorbs the  sunlight and helps in photosynthesis process.  The colour of this pigment is green and therefore most of the plants exhibit green  colour. But when there will be no sunlight, no photosynthesis takes place and as plant will not get energy there will be no chlorophyll in the plant after some time and thus plant start becoming yellow in  the absence of light. 2. Which raw materials are responsible for the release of O2, in photosynthesis? Ans:   Water and carbon-dioxide are the two raw materials responsible for the release of oxygen during photosynthesis. Water is absorbed from soil th

  Electricity AC : An electric current whose magnitude changes with time and direction reveres periodically is called alternating current . It is denoted by AC. Source of AC are hydro-electric generators, thermal power generations and nuclear power generators etc. The number of cycles completed by the AC in one second is called the frequency of AC. The frequency of AC in India is 50 Hz. Frequency 50 Hz means that AC changes its directions after 1/100 second. DC: An electric current whose magnitude is either constant or variable but the direction remains the same is called Direct current. It is denoted by DC. Sources of DC are voltaic cell, a dry cell, battery, DC generators etc. MAJOR DIFFERENCE BETWEEN AC AND DC: AC: Alternate Current        AC reverses its direction periodically.        Electric power can be transmitted over long distances without much loss of energy.        Alternating voltages can be stepped up or stepped down as per requirement, using transformer. DC: Direct Cur

Life Process   ( Assertion and Reasoning Questions ) Following questions consist of two statements – Assertion (A) and Reason (R).  Answer these questions selecting the appropriate option given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is not the correct explanation of A. (c) A is true but R is false. (d) A is false but R is true. 1. Assertion: Interauricular septum separates left ventricle from right atrium.     Reason: Interventricular septum separates left ventricle from right ventricle 2. Assertion: All the arteries carry oxygenated blood from the heart to various organs.    Reason: Pulmonary vein carries deoxygenated blood to the heart. 3. Assertion: Translocation of sugar occurs through the phloem.      Reason: It is achieved by diffusion of sugars through phloem. 4. Assertion: Resins and gums are stored in old xylem tissue in plants.     Reason: Resins and gums facilitates transport of water molecules. 5. Assertion: L

  LIGHT  REFLECTION AND REFRACTION 1. Write down four important characteristics of image formed by a plane mirror. Ans: Image is virtual, erect, laterally inverted and same size as object. 2. Define the following terms in relation to concave spherical mirror: a. Pole b. Centre of curvature c. Radius of curvature d. Principal focus e. Principal axis f. aperture g. Focal length Ans:  a. Pole : The mid point of the mirror is known as Pole. b. Centre of curvature:  The centre of curvature of a spherical mirror is the centre of that sphere of which mirror is a part. c. Radius of Curvature: The distance between pole and centre of curvature is called radius of curvature of the mirror. d. Principal Focus: The point on the axis of a mirror to which parallel rays of light converge or from which they appear to diverge after reflaction. e. Principal axis:   The straight line passing through the pole and the center of curvature of the spherical mirror  is called the principal axis of a spherical

Chemical Reactions and Equations ( Assertion and Reasoning Questions ) Following questions consist of two statements – Assertion (A) and Reason (R).  Answer these questions selecting the appropriate option given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both A and R are true but R is not the correct explanation of A. (c) A is true but R is false. (d) A is false but R is true. 1. Assertion (A) : Decomposition of vegetable matter into compost is an example of exothermic reactions. Reason (R) : Exothermic reaction are those reactions in which heat is evolved. 2. Assertion (A) : When HCl is added to zinc granules, a chemical reaction occurs. Reason (R) : Evolution of a gas and change in colour indicate that the chemical reaction is taking place. 3. Assertion (A) : Calcium carbonate when heated gives calcium oxide and water. Reason (R) : On heating calcium carbonate, decomposition reaction takes place. 4. Assertion (A) : Brown fumes are produced when

  Chapter - 15 Our Environment  ( Assertion and Reasoning Questions )   👀 Each of these questions contains an assertion followed by reason.   👀  Read them carefully and answer the question on the basis of following options. You have to select the    one that best describes the two statements. (a) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion. (b) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. (c) If Assertion is correct but Reason is incorrect. (d) If Assertion is incorrect but Reason is correct. 1.  Assertion (A) : In an ecosystem, the function of producers is to convert inorganic compounds into                                      organic compounds.       Reason: (R) : Green plants, the producers, transduce solar energy. 2.  Assertion (A) : Ecology is study of relationship between living organisms and their environment.             Reason (R) :    The biotic community and non-living

  Electricity  Very Short Answer Type Questions👇  1. By what other name is the unit Joule⁄Coulomb called?  Ans: Potential Difference is said to be 1 Volt between two points if 1 Joule of work is done in moving 1 coulomb of electric charge from one point to another.  2. Which of the following statements correctly defines a volt?  (a) A volt is a joule per ampere.  (b) A volt is a joule per coulomb .   Ans: The second statement defines "volt" correctly.  Explanation : One Volt is the electric potential energy per unit charge, and is measured in joules per coulomb.  3. What do the letters p.d. stand for?   Ans:   p.d. stands for potential difference . Potential difference between two points in a circuit is the work done in moving unit charge (i.e. one coulomb) from one point to the other.  4. Which device is used to measure p.d.?   Ans: Voltmeter is a device which is used to measure potential difference between two point in an electric circuit.  5. What is meant by saying

  Magnetic Effect of Electric Current 1.G ive reason for the following: (i) There is either a convergence or a divergence of magnetic field lines near the ends of a current carrying straight solenoid. (ii) The current carrying solenoid when suspended freely rests along a particular direction.   Ans: (i) There is either a convergence or a divergence of magnetic field lines near the ends of a current carrying straight solenoid because it behaves similar to that of a bar magnet and has a magnetic field line pattern similar to that of a bar magnet. Thus the ends of the straight solenoid behaves like poles of the magnet, where the converging end is the south pole and the diverging end is the north pole. (ii) The current carrying solenoid behaves similar to that of a bar magnet and when freely suspended aligns itself in the north-south direction. 2 .  Find the direction of magnetic field due to a current carrying circular coil held: (i) vertically in North – South plane and an observer looki

  Lymphatic System A system of lymph vessels and lymph nodes in the human body which transports the lymph from the body tissues to the blood circulatory system is called LYMPHATIC SYSTEM. The lymphatic system consists of the following parts: (i) Lymph capillaries (ii) Larger lymph vessels (iii) Lymph nodes (iv) Lymph LYMPH : Lymph is a colourless liquid which somewhat similar in composition to plasma. Important points for Lymph: 1. Lymph contains large protein molecules and digested food. 2. Lymph also contains germs from the cells and fragments of dead cells. 3. Lymph is another medium of circulation in the human body. 4. Lymph flows in only one direction from body tissues to the heart. 5. Lymph contains a special type of white blood cells called LYMPHOCYTES which help in fighting infection and disease. The Functions of Lymph ( Lymphatic System) 1. Lymph takes part in the nutritive process of the body. 2. Lymph carries digested fat for the nutritive process. 3. Lymph protects the bod

  Important : Control and Coordination 1. What are ‘hormones’? State one function of each of the following hormones:          (i) Thyroxine (ii) Insulin Ans . Hormones are the chemical substances which coordinate and control the activities of living organisms and also their growth.          (i) Function of Thyroxine:           This hormone regulates the metabolism of carbohydrates and fats.         (ii) Function of insulin:          This hormone helps in regulating sugar level in the blood. 2. Name and explain the function of the hormone secreted by the pituitary gland in humans. Ans. Hormones secreted by pituitary gland along with their functions are:        1. Growth hormone : It regulates growth and development of bones and muscles.        2. Trophic hormone : It regulates secretion of hormones from other endocrine glands.        3. Prolactin hormone : It regulates the function of mammary glands in females.        4. Vasopressin hormone : It regulates water and electrolyte balance

  Important Q/A Electricity Q. 1. If a body has positive charge, then what does it mean? Ans:   If a body has positive charge it means that it has less no. of electrons than the no. of protons. Due to this imbalance of the charges, the body will attract the negative charged body. Q. 2. In which direction does current flow in an electric circuit? Ans:   In an electrical circuit the current flows from the positive to the negative. The conventional current always flows in the direction opposite to the direction of flow of the electron. Q. 3. Write a low resistance device name which is always connected in series with the device through which the current is to be measured. \ Ans:   Ammeter is a device that is connected in series so as to measure the current through the circuit. It has a very low resistance so that maximum current passes through it and thus the correct amount of current through the circuit can be measured. Q. 4. Write a high resistance device name which is always connected i

  1. List the factors on which the resistance of a uniform cylinder conductor of given material depends. And: Factors on which the resistance of a conductor depends: (I) Length of conductor:  Resistance is directly proportional to the length of conductor. This means resistance increase with increase in length of the conductor.  This is why long wirescreate more resistance to the electric current. (ii) Area of cross section:  Resistance is inversely proportional to the area of cross section of the conductor. This means resistance decrease with increase in area of cross section of conductor and viceversa. This is why, a thick copper wire create less resistance to electric current. (iii) Temperature : Resistance is directly proportional to the temperature. (iv) Nature of material : Resistance depends on nature of material. Some materials like silver are good conductor of electricity while some like plastic are bad conductor of electricity.

  Important Biology 1. Placenta is extremely essential for foetal development. Give reason. Ans:  1. The developing embryo gets nutrition from the mother's blood with the help of placenta. 2. Placenta contains villi on the embryo's side of the tissues and blood spaces on the mother's side surround the villi provide a large surface area that facilitates passages of nutrition and oxygen to embryo from mother through blood. 3. Waste substances produced by embryo are removed through placenta into mother's blood. 2. Uterine lining becomes thick and spongy after fertilization. give reason. Ans: Every month one egg is released by the ovary and uterus prepares itself to receives a fertilized egg. As a result, the lining of the uterus becomes thick and spongy. This is required for nourishing and embryo after fertilization. 3. Name the reproductive and non reproductive parts of the bread mould. Ans: 1. Reproductive part: Sporangia (knob like structure)          2. Non reproductiv