NCERT Solutions Class 8 Science Chapter 12 Some Natural Phenomena

Class 8 science chapter 12 - Some Natural Phenomena will introduce students to two important natural phenomena- lightning and earthquakes and the preventive measures which can be taken to reduce destruction caused by these phenomena.

This Article contains NCERT Solutions for Class 8 Science Some Natural Phenomena prepared by some of India’s top subject matter experts at ALLEN. Some natural phenomena Class 8 NCERT Solutions are presented in a clear and comprehensive manner so that the students can easily grasp the concepts. In addition, by solving the class 8 science chapter 12 some natural phenomena question answer, the students will be able to learn the important areas of the chapter and the nature of the questions they are likely to encounter in the examinations, which will help them prepare for the tests. Very often, questions appearing in the final exams come precisely from the NCERT textbooks.

Along with NCERT Solutions, students can also take help from some natural phenomena NCERT Solutions for Class 8 Science notes which give a brief overview of all the topics in class 8 some natural phenomena which prove to be helpful for students in their last minute exam revision.

1.0NCERT Solutions for Class 8 Science Chapter 12 PDF

Students can download some natural phenomena class 8 solutions from the table below which are available to be downloadable in pdf format for easier accessibility.

2.0NCERT Questions with Solutions Class 8 Science Chapter 12 - Detailed Solution

• Which of the following cannot be charged easily by friction? (a) A plastic scale (b) A copper rod (c) An inflated balloon (d) A woollen cloth. Solution Option (b) is correct. Insulating materials can be easily charged by friction. Copper is a highly conducting material. Therefore, a copper rod cannot be charged easily by friction.
• When a glass rod is rubbed with a piece of silk cloth the rod (a) and the cloth both acquire positive charge. (b) becomes positively charged while the cloth has a negative charge. (c) and the cloth both acquire negative charge. (d) becomes negatively charged while the cloth has a positive charge. Solution Option (b) is correct. The glass rod becomes positively charged, while the silk cloth has a negative charge. When an object is charged by rubbing it against another object, the two objects get oppositely charged. By convention, it is considered that the charged acquired by the glass rod is positive and charged acquired by the cloth is negative.
• Write $T$ against true and $F$ against false in the following statements: (a) Like charges attract each other (T/F) (b) A charged glass rod attract a charged plastic straw (T/F) (c) Lightning conductor cannot protect a building from lightning (T/F) (d) Earthquakes can be predicted in advance (T/F) Solution (a) False Like charges repel each other, unlike charges attract each other. (b) True A charged glass rod has a positive charge while a charged plastic straw has a negative charge thus, they attract each other as unlike charges attract each other. (c) False Lightning conductor is a device to protect a building against lightning. (d) False Although the causes of earthquakes is known, but no instrument could be invented to detect it till now. Hence, earthquakes cannot be predicted in advance.
• Sometime, a crackling sound is heard while taking off sweater during winters. Explain. Solution When a sweater is taken off, the woollen sweater gets charged because of the friction between the sweater and the body. Thus, an electric discharge (spark) takes place between the body and the sweater. This produces a crackling sound, even a spark (light) can be see if the sweater is taken off in a dark room.
• Explain why a charged body loses its charge if we touch it with our hand. Solution When we touch a charged object, our body conducts its charges to the earth. That is why a charged body loses its charge, if we touch it with our hand.
• Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage? Solution The Richter scale has the readings from 1 to 10 . The reading of magnitude 3 on the Richter scale would be recorded by a seismograph. If the Richter scale gives a reading of magnitude 3 , then the earthquake is not likely to cause much damage. Generally, earthquake of magnitudes higher than 7 is considered destructive in nature.
• Suggest three measures to protect ourselves from lightning. Solution (1) If you hear thunder, rush to a safer place like a house or a building. If you are travelling by car or by bus, you are safe inside with windows and doors of the vehicle shut. (2) Lightning can strike telephone cords, electrical wires and metal pipes. During a thunderstorm contact with these should be avoided. (3) Bathing should be avoided during thunderstorms to avoid contact with running water.
• Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon? Solution The nature of charges present on the surface of charged balloons are similar. Since like charges repel each other, two charged balloons repel each other. When a charged body is brought near an uncharged body, the near end of the uncharged body acquires opposite charge and far end acquires similar charge due to process of induction. Since the opposite charge is near as compared to the similar charge, there is a net attractive force between them. Hence, an uncharged balloon is attracted by another charged balloon.
• Describe with the help of a diagram an instrument which can be used to detect a charged body. Solution The leaf electroscope is an instrument used to detect the presence of electric charge on a body. It contains a vertical metal rod, with a round metal ball or knob on top, housed in a box. The metal rod and the box are insulated with each other by hard rubber or amber. Two very thin leaves of gold (or aluminium) are attached to bottom end of the rod. Detection of presence of charge on a body using electroscope : When the electroscope is uncharged, the two leaves hang parallel and vertically downwards due to its own weight [see figure(a)]. Suppose a negatively charged rod touches the knob. Because the metal is a good conductor, electrons travel down the rod into the leaves.Both the leaves become negatively charged as they gain electrons [see figure(b)]. Because the leaves have similar charges, they repel each other. When the positively charged glass rod is brought into contact with the metal knob of an uncharged electroscope, electrons flow out of the metal leaves and onto the rod. The leaves repel each other because each leaf becomes positively charged as it loses electrons [see figure(c)].

• List three states in India where earthquakes are more likely to strike. Solution Jammu and Kashmir, Gujrat, and Uttaranchal.
• Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself? Solution (1) Try to find a clear spot, away from buildings, trees and overhead power lines. Drop to the ground. (2) If you are in a car or a bus, do not come out. Ask the driver to drive slowly to a clear spot. Do not come out till the tremors stop.
• The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain. Solution Carrying umbrella is not a good idea at all during thunderstorms. As a lightning flash travels toward the ground from a nearby cloud, it looks for the tallest object. This is because all the objects attached to the ground acts as ground or earthed objects. So lightning takes the shortest path to travel and thus, falls on the tallest object. If you're holding an umbrella in an area surrounded by taller buildings, it's not so risky. But if you are the only tall object in the place surrounding you, the lightning flash will fall on you. Thus, carrying umbrella is not a good idea at all during thunderstorms.

3.0What Will Students Learn in Chapter 12: Some Natural Phenomena?

• Lightning: Its occurrence, the scientific explanation of it, and safety precautions to avoid damage during a thunderstorm.
• Earthquakes: What causes earthquakes, how do we measure them, and measures to reduce impact.
• Electrostatic Charge: Phenomenon of static electricity and its significance from nature's perspective.
• Protection from Natural Hazards: Strategies and strategies available to protect from lightning and earthquakes.