CBSE Class 8 Science Chapter 12 Some Natural Phenomena Short Answer Questions
Question 1. You might have observed on a dry day that when you touch the screen of a television or computer monitor (with a picture tube), you get a slight shock. Why does it happen?
Answer: It happens because the television screen or computer monitor is charged and has static charges. When we touch them with our hands, which are uncharged, the charges attract our hands and transfer through our hands, and we get a small shock.
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Question 2. In an electroscope, if a negatively charged body is brought in contact with the metal clip, the strips of the electroscope diverge. If another charged object carrying an equal amount of positive charge is brought in contact with the clip, what will happen?
Answer: As it is clear from the figure, whether we bring a positive or negative rod, the strips will always repel because an equal amount of charges are transferred to the strips, and like charges always repel each other.
” Cbse Class 8 Science Chapter 12 Saqs “
Question 3. The strips of an electrosope diverge when a charged body is brought in contact with the Mental cup. Now, the clip is touched gently by our hand. What will happen to the strips? explain
Answer: If we touch the strip while standing on ground (not on any insulating base), the charges will pass through our hand to the ground because they will get the path to flow and strips will not diverge.
Question 4. During the construction of a building, the lightning conductor was left hanging in the air by mistake. Would the lightning conductor still be effective? Explain.
Answer: Lightning conductor will not work, it left hanging in the air because in order to work, it must be installed properly and grounded using any metal (copper) plate.
” Tectonic Plates And Earthquakes “
Question 5. Explain the concept of the lightning rod. Also, explain how it protects the buildings?
Answer: The device which is used to protect tall buildings from the effect of lightning is called lightning conductor. Also, metallic rod is installed in the walls of the buildings during its construction and one end of the rod is kept out in air and the other end is fixed in the ground. So, it provides an easy route for transfer ofelectric discharge to the earth.
Question 6. Identify the lightning conductor and the copper plate in the figure.
Answer:
” Some Natural Phenomena Class 8 “
Question 7. Give the name of the scientist who established the relation between sparks produced by amber and thunderstorms. Explain in brief.
Answer: There was an American scientist, Benjamin Franklin, who established that sparks produced by amber are similar to the sparks produced by thunderstorm. For this, he flew a kite tied with a silken thread which had an iron key attached to it on rainy day. So, during lightning, he experienced the shock through iron key, which proved that clouds also carried charges.
Question 8. If air and cloud are good conductors of electricity, do you think lightning could occur? Explain.
Answer: No, there will not be lightning at all because all the charges collected in the clouds will continuously transfer through the air, and there will be no lightning.
Question 9. Explain the electric discharge that occurs in clouds.
Answer: During thunder, negative charges accumulate near the clouds, and positive charges accumulate near the ground.
So, when these charges meet, then electric discharge takes place between ground and clouds. So a large amount of energy released in the form of thunder and lightning.
Question 10. If the materials used for constructing a building were good conductors, do you think lightning would strike the building? Will the lightning conductor still be required to be installed in the building?
Answer: Lightning will not strike the building in such a case because all the lightning striking the building will reside on the surface of the building. Now, there is no need to install any lightning conductor because all the work oflightning conductor is done by the conducting material itself.
” Earthquake Causes And Effects “
Question 11. Mention three precautions that you will take to protect yourself if an earthquake strikes when you are
Answer: Three precautions during an earthquake inside the house are as follows
- Instead of running away, we should get under a desk, table, or bench.
- Pick a safe place where things will not fall on you, away from windows, bookcases or tall heavy furnitures.
- Wait at your safe place until the shaking stops.
Question 12. Is it possible to predict the occurrence of an earthquake?
Answer: No, scientists have tried lots of different ways of predicting earthquake but none have been successful so far. They have a pretty good idea of where an earthquake is most likely to hit but they still cannot tell exactly when it will happen.
” Static Electricity Experiments Class 8 “
Question 13. What is an earthquake?
Answer: An earthquake is a sudden shaking or trembling of the earth that lasts for a very short time.
Question 14. What causes an earthquake?
Answer: The outermost layer of the Earth is fragmented. Each fragment is known as a plate. These plates are in continuous motion. When these plates collide with one another, they cause disturbance in the Earth’s crust. This disturbance shows up as an earthquake on the Earth’s surface.
” Lightning And Thunder Explanation “
Question 15. What could cause a disturbance inside the Earth?
Answer: The movement of tectonic plates, when it collide with one another, then it cause a disturbance inside the Earth.