Some Natural Phenomena Question Answers: NCERT Class 8 Science

Welcome to the Chapter 15 - Some Natural Phenomena, Class 8 Science - NCERT Solutions page. Here, we provide detailed question answers for Chapter 15 - Some Natural Phenomena.The page is designed to help students gain a thorough understanding of the concepts related to natural resources, their classification, and sustainable development.

Our solutions explain each answer in a simple and comprehensive way, making it easier for students to grasp key topics and excel in their exams. By going through these Some Natural Phenomena question answers, you can strengthen your foundation and improve your performance in Class 8 Science. Whether you're revising or preparing for tests, this chapter-wise guide will serve as an invaluable resource.

Some objects can be charged by rubbing with other objects.
There are two kinds of charges: positive and negative.
Like charges repel and unlike charges attracts.
The process of transfer of charge from the charged object to the earth is called earthing.
The process of electric discharge between clouds and the earth or between different clouds causes lightening.
Lightening conductors can protect building from the lightening effects.
Earthquake is caused by the disturbance inside the crust.
Destructive energy of an earthquake measured on Richter scale. The earthquake measuring one or more on Richter scale can cause damage to life and property.
Earthquake generally occurs at the boundaries of the Earth’s plate. These boundaries are called as fault zone.
Topmost layer of the earth is called as crust.
Discharge may be defined as the transmission of electricity through a medium in an applied electric field.
Electroscope is an instrument which is used to detect the presence of the electric charge on body.
In a dark sky, on a rainy day, when a shiny streak of light appears accompanied with the thunder is called as lightening.
An instrument which is used to record the details of earthquake is known as seismograph.
Sound caused by the lightening is called as thunder.
A storm with lightning and thunder is known as thunderstorm.
The giant waves which are caused by earthquake or volcanic eruptions under the sea called as tsunami.

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Exercise 1 ( Page No. : 199 )

Q1	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.
Ans:	(b) Copper rod Copper rod can be easily changed by friction because it is a highly conducting material. Non- conducting materials are the only one which can be easily charged by friction.

Q2	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.
Ans:	(b) Becomes positively charged while the cloth has a negative charge. On rubbing two objects becomes charged, they get oppositely charged. By convention it is assumed that the charge acquired by the cloth is negative and the charge acquired by the glass rod is positive.

Q3	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)
Ans:	(a) False This statement is false because like charges repel each other whereas opposite charges attracts each other. (b) True This statement is true because a charged plastic straw has negative charge and a charged glass rod acquires positive charge. As we know opposite charge attract each other, so the charged glass rod attracts the charged plastic straw. (c) False This statement is false because a lightening conductor conducts all the atmospheric charges to the Earth directly during a lightening, leaving the building safe. (d) False This statement is false because there is no such instrument which detect the upcoming earthquake.

Q4	Sometime, a crackling sound is heard while taking off sweater during winters. Explain.
Ans:	During winters, while taking off a sweater, a crackling sound is heard. This is because the particles of sweater gets charged and these particles attracts or repel each other when they comes in contact with each other. Hence, due to this attraction or repulsion, a cracking sound is produced.

Q5	Explain why a charged body loses its charge if we touch it with our hand.
Ans:	The human body is a conductor, so when we touch a charged body, the charge passes through our body to the ground and the body loses its charge. This discharging phenomena is known as electric discharge.

Q6	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?
Ans:	The destructive energy of an earthquake is measured on the Richter scale. It has readings 1 to 10. An earthquake measures 3 on this scale can be recorded by a seismograph. It does not cause much damage.

Q7	Suggest three measures to protect ourselves from lightning.
Ans:	Measures to protect ourselves from lightening are as follows: Take shelter in a house or building. Do not take a bath under running tap water. Do not stand under a tree. Do not touch conducting materials like electric wires, poles etc. Do not use umbrella with a metallic rod. Do not run across a large open field. If you cannot find a safe place, squat down in a low lying place. Unplug all the electrical appliances if you are at home. Do not use landline phones.

Q8	Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
Ans:	When a charged balloon is placed near an another charged balloon. They repel each other due to like charges present on them. However, a charged balloon attracts an uncharged balloon because it induces an unlike charge on the near surfaces of the uncharged balloon.

Q9	Describe with the help of a diagram an instrument which can be used to detect a charged body.
Ans:	An electroscope can be used to detect whether a body is charged or not. In an electroscope, two metal foils are hanged with the help of a conductor in the glass jar with lid. When a charged body touches this conductor then its charges get transferred to the metal foil and they separates due to like charges. This shows that an electroscope detect charges.

Q10	List three states in India where earthquakes are more likely to strike.
Ans:	In India, earthquakes are more likely to strike in Gujrat, Rajasthan and Kashmir.

Q11	Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?
Ans:	The following precautions can be taken to protect from an earthquake when we are outside our home: Find a clear spot away from the buildings, trees and overhead power lines. If you are in a car, do not come our till the tremors stop. Ask the driver to drive the car or bus slowly to the clear spot.

Q12	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.
Ans:	The umbrella has a metallic rod with a sharp point. It is a good conductor and allows electric current to pass through it. If there is a lightening, it would be dangerous to move under the umbrella. So, I would not carry an umbrella when going out the day on which the weather department has predicted a thunderstorm.