Saturday, 20 April 2013

Chapter 16. LIGHT | Science | CBSE Class VIII (8th) | Solved Exercises

Question 1. Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room. Explain.

Answer : We can not see objects in the dark room without the presence of light or a lighted object it self . We may see an object only when, the light from an object enters our eyes.

Sunday, 14 April 2013

Chapter 15. SOME NATURAL PHENOMENA |Science | CBSE Class VIII (8th) | Solved Exercises

Select the correct option in Questions 1 and 2.
Question 1. Which of the following cannot be charged easily by friction?

  1. (a) A plastic scale
  2. (b) A copper rod
  3. (c) An inflated balloon
  4. (d) A woolen cloth.
Answer : (b) A copper rod

Monday, 8 April 2013

Chapter 14. CHEMICAL EFFECTS OF ELECTRIC CURRENT | Science | CBSE Class VIII (8th) | Solved Exercises

Things to remember....

  1. Some liquids are good conductors of electricity and some are poor conductors.
  2. Most liquids that conduct electricity are solutions of acids, bases and salts.
  3. The passage of an electric current through a conducting liquid causes chemical reactions.
  4. The resulting effects are called chemical effects of currents.
  5. The process of depositing a layer of any desired metal on another material, by means of electricity, is called electroplating.

Friday, 5 April 2013

Chapter 13. SOUND |Science | CBSE Class VIII (8th) | Solved Exercises

Things to remember....

  1. Sound is produced by vibrating objects.
  2. In human beings, the vibration of the vocal cords produces sound.
  3. Sound travels through a medium (gas, liquid or solid). It cannot travel in vacuum.
  4. It sends the signals to the brain. This process is called hearing.
  5. The number of oscillations or vibrations per second is called the frequency of oscillation.

Chapter 12. FRICTION |Science | CBSE Class VIII (8th) | Solved Exercises

Things to remember....

  1. Friction opposes the relative motion between two surfaces in contact. It acts on both the surfaces.
  2. Friction depends on the nature of surfaces in contact.
  3. For a given pair of surfaces friction depends upon the state of smoothness of those surfaces.