CBSE ADDA

The first direct experimental evidence for the electrical nature of matter came from the experiments of  Michale Faraday . He showed from his experiments that electricity is composed of particles called ‘atoms of electricity’. It was  George Johnstone Stoney , an Irish Physicist who first proposed the word ‘ electron ‘ for atom of electricity’ in 1891.His contribution to research in this area laid the foundations for the eventual discovery of particles by  J.J. Thomson in 1897. In 1878, Sir William Crooke,  while conducting an experiment using a  discharge  tube, found certain visible rays travelling between two metal electrodes. These rays are known as Crooke’s Rays or  cathode rays . The  discharge  tube used in the experiment is now referred to as Crookes tube or more popularly as Cathode Ray  Tube (CRT). Cathode Ray Tube :  It i...

Q1 What is meant by electric current? Ans-Electric Current : Flow of electrons. Q2 What is an electrc circuit? Ans -Electric Circuit : The closed path in which electric current flows. Q3 Under what conditions a circuit is said to be complete? Ans-Current can flow through a circuit only if it is complete i.e. all its parts are made up of a conductor. Q4 What is a switch? Ans -Switch is used to close and open a circuit. When switch is ‘ON’ circuit is complete and current flows through it and when it is ‘OFF’ circuit breaks (air is an insulator) and flow of current stops. Q5 Draw the symbols for various Components of an electric circuit ? Cell : Source of electric current.   Battery : Combination of 2 or more cells  Connecting Wires – generally insulated Copper wires.  Electric Bulb – Key or switch-Open key-Closed key Note : When cells are connected to form a battery positive terminal of one is always connected to negative terminal of the other. Q6 What is a ...

7th WASTE WATER STORY Q1. State various uses of water. Ans. Water is used for: • Drinking • Cooking • Washing clothes, utensils • Generating electricity • Bathing • Habitat for various organisms etc. Q2. What is waste water? Ans. The dirty water which contains various impurities like dust, polythene bags, Vegetable peels, kitchen waste, oil & water that goes down the drains from sinks, showers, toilets, laundries etc is waste water. Waste water can not be used further. Q3. What are the various causes of water pollution? Ans. water is polluted by various factors like: • Bathing of cattle in river bodies. • Washing of clothes & utensils by people in rivers. • Discharging wastes from factories, industries in nearby river bodies & ponds. Q4. When is World Water Day celebrated? Ans. World Water Day is celebrated on 22nd March. Q5. What is sewage? Ans. The waste water that is being generated at homes, industries, agricultural activities, human a...

Objective type Questions: 1. Out of convex mirror and concave mirror, whose focus is situated behind the mirror? Ans: The focus of convex mirror is situated behind it. 2. For what position of an object, a concave mirror forms an enlarged virtual image? Ans: Object between pole (P) and focus (F) of the concave mirror. 3. If the focal length of a concave mirror is 25cm. What is its radius of curvature? Ans: Focal length = Radius of curvature / 2 25 = R / 2 R = 25 X 2 = 50cm. 4. A ray of light falls on a mirror normally. What are the values of angle of incidence and the angle of reflection? Ans: Both angle of incidence and the angle of reflection are zero. 5. What is the focal length of a plane mirror? Ans: Infinite. 6. Which spherical mirror is called a divergent mirror? Ans: A convex mirror is called a divergent mirror. 7. What is the angle of incidence, when a ray of light falls on the spherical mirror from its centre of curvature? Ans: The angle of incidence is zero, w...

REPRODUCTION IN PLANTS CLASS7th CORE ASSIGNMENT Q1. Describe the different methods of asexual reproduction . Give examples. A.There are different methods by which plants reproduce asexually. They are vegetative propagation, budding,fragmentation and spore formation. The vegetative parts of a plant are the roots, stems and leaves. When new plants are produced from these parts, the process is called vegetative propagation. 1. Budding- A bulb like projection grows on the parent organism. It grows and may eventually break away from the parent. E.g. yeast, hydra, corals, sponges. 2. Fragmentation- The organism breaks up into two or more fragments after maturation. These fragments grow into new individuals. E.g. spirogyra, hydra 3. Spore formation- A spore is a tiny, spherical and unicellular body protected by a thick wall. Under favourable conditions, a spore germinates and develops into a new individual. E.g. mosses, ferns, moulds Q2. Describe the various ways by w...

OBJECTIVES OF THIS LESSON Periodic Classification of Elements After completing this lesson, you will be able to: ! state different historical classifications of elements in brief; ! state main features of Mendeleev’s periodic table; ! explain the defects of Mendeleev’s periodic table; ! state modern periodic law; ! describe the features of the long form of periodic table; ! define various periodic properties; ! discuss the trends in various periodic properties in the periodic table. The first classification of elements was as metals and non-metals. This served only limited purpose mainly because of two reasons: 1. All the elements were grouped in to these two classes only. The group containing metals was very big. 2. Some elements showed properties of both-metals and non-metals and they could not be placed in any of the two classes. Dobereiner’s triads In 1829, Dobereiner, a German scientist made some groups of three elements each and called them triads.He obs...

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CBSE MATH STUDY: 9th 10th CBSE Sample paper for maths and science 2... GENERAL INSTRUCTIONS : 1. All questions are compulsory. 2. The question paper consists of 34 questions divided into four sections, namely Section A : 10 questions (1 mark each) Section B : 8 questions (2 marks each) Section C : 10 questions (3 marks each) Section D : 6 questions (4 marks each) 3. There is no overall choice. However, internal choice has been provided in 1 question of two marks, 3 questions of three marks and 2 questions of four marks each. 4. Use of calculators is not allowed. 10th_maths_sample_paper_2011-2012 - 1 Download File 10th_maths_sample_paper_2011-2012 - 2 Download File 10th_maths_sample_paper_2011-2012 - 3 Download File Fore more solved sample paper visit NEW Addition

CBSE PHYSICS: X phy Human Eye and Colourful World : X CBSE PHYSICS Questions for Practice 1. A person can see only objects beyond 1m. From his eyes. Name the defect of the eye. 2. Out of lig...

chemistry adda: X Science Guess Paper – 2012 Carbon and its compou... : Guess Paper – 2012 Class – X Subject - Science Carbon and its compounds Answer the following questions: Section A – one mark ea...

CBSE PHYSICS: IX Science WORK, POWER AND ENERGY Guess Paper – 2... : 1. What is the work done by a force equal to? 2. Name two factors on which kinetic energy depends. 3. What is the commerc... CBSE PHYSICS

MCQ and Study notes Air pollution is described as any change in the composition of air either by physical or chemical methods so as to cause harmful effects on health. The substances which contaminate the air are called air pollutants. Sources of Air Pollution are : 1. Natural sources 2. Man-made (anthropogenic) sources. Natural sources: Volcanic eruption, forest fire, sea salt sprays, biological decay, photochemical oxidation of terpenes oil , marshes, pollengrains, spores, etc., Man made sources : Industrial emissions, vehicles, aeroplanes, power stations and burning of fuels, etc., Mainly air pollution is caused due to burning of fuels to run vehicles, and from chimneys of factories and power stations. The Green House Effect : Some of the infrared radiation from the earth passes through the atmosphere but most is absorbed and re-emitted in all directions by greenhouse gas molecules and clouds. This warms up the Earth’s surface and the lower atmosphe...

CTET/TET Sample Model Question Paper 2012  Child development and Pedagogy CTET examination papers can be downloaded from given link Mathematics Science  English Language child-pedagogy CTET or Other state Tet model paper

CBSE PHYSICS: IX Physics Sound NCERT Solutions Explain how sound is produced by your school bell. When the bell continues to move forward and backward, it creates a series of compressions and rarefactions. In this  way a bell  produce the sound . Why sound waves are called mechanical waves? Sound waves need the material medium to vibrate and propagate. Hence, these waves are known as mechanical waves. Sound waves propagate through a medium because of the interaction of the particles present in that medium. Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend? Sound needs a medium to propagate. Since there is no material medium on the moon due to absence of atmosphere, you cannot hear any sound on the moon. Page 166 : Which wave property determines (a) loudness, (b) pitch? (a) Amplitude of sound wave determines the loudness of a sound. The amplitude of a sound directly proportional to amplitude of wave. If the amplitude...