CBSE ADDA

Page 47          1. What are canal rays? Ans: Canal rays are positively charged radiation s that can pass through perforated cathode plate. These rays consist of positively charged particles known as protons 2. If an atom contains one electron and one proton, will it carry any charge or not? Ans: An atom containing one electron and one proton will not carry any charge they make an atom neutral. Page 49 3. On the basis of Thomson’s model of an atom, explain how the atom is ne utral as a whole. Ans:  According to Thomson’s model of the atom, an atom consists of equal number of negatively and positively charged particles. The negatively charged particles are embedded in the positively charged sphere and balance their charges. Thus, they make an atom neutral. 4. On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom? Ans: protons (positively-charged particles) 5. Draw a sketch of Bohr’s model of an atom w

1. A bat ate 1050 dragon flies on four consecutive nights. Each night she ate 25 more than on the night before. How many did she eat on first night?  (a) 225         (b) 250    (c) 275         (d) 300 Sol:  (a) Let no. of dragonflies ate by bat an first day = x   and   second day = x + 25   third day  = x + 50  fourth day  = x + 75    A/Q   x + x + 25 + x + 50 + x + 75 = 1050  x = 224 2. A cuube has  (a) 8 vertices, 12 edges and 6 flat surfaces.               (b) 4 vertices, 6 edges, 6 flat surfaces. (c) 4 vertices, 12 edges and 4 flat surfaces.  (d) 8 vertices, 6 edges, 4 flat surfaces. Sol:  (a) 4. In the word Mathematics , the ratio of number of consonants to the number of vowels is (a) 4:7 (b) 7: 4 (c) 5:6 (d) 6:5 Sol: (b) 7:4 5. Who is the father of Geometry?     (a) Pythagoras (b) Thales    (c) Archimedes (d) Euclid. Sol: (d) Euclid 6. A milkman mixes 20 liters of water with 80 liters of milk. After selling one-fourth of this m

8 th      Stars and the solar system    Assignment                     1.  Define:  Celestial objects, Phases of Moon, Light year, Constellation, Asteroids, Meteors, Meteorite, Comets, and Crescent Moon 2. Why do phases of moon occur? 3. Explain the surface of moon. 4. What is the distance of the Alpha centaury? 5. Why does stars appears to move from East to West? 6. Why does pole star does not appear to move? 7. Name a constellation which can be seen (a) during summer  (b) during winter 8. How can we locate pole star using the constellation Ursa major (draw diagram also) 9. Name the brightest star in the sky which is located closed to Orion 10. (a) Name the planet nearest to Sun                                          (b)Name the brightest planet in the sky       (c)Which planet is often called a morning or an evening star?       (d)Name a planet which rotates from east to west       (e)Which planet is called Red planet?        (f)Which is the la

Work sheet: Subject – Maths, Class – VIII- Chapter: Probability 1. A coin is tossed twice. Find the robability of getting both tails? 2. Find the probability of getting even number between 10 to 25. 3. A die is thrown once. Find the probability of getting a prime number. 4. One card is drawn from a well shuffled deck of 52 cards. Find the probability of getting a face card. 5. What is the maximum value of the probability for an event? 6. A bag contains 9 red, 7 white and 4 black balls. A ball is drawn at random. Find the probability that the ball drawn is not red. 7. In the word “EDUCATION” find the probability of getting a vowel. 8. Out of 400 bulbs in a box, 15 bulbs are defective. One bulb is taken at random from the box. Find the probability that the bulb is not defective. 9. A die is thrown once. What is the probability of getting a multiple of 3. 10. A card is drawn from a pack of 52 cards. Find the probability of drawing a red face card. 11. A bo