NCERT Solutions Class 8 Science Chapter 15

NCERT Solutions for Class 8 Chapter 15

Learning about the natural world using observation and experimentation is known as science. Scientists gain knowledge of the natural world by conducting studies that provide evidence that helps answer their questions. Experiments or observations of the natural environment are a part of the research. Scientists conduct research using different scientific methods. Science is divided into several branches, each of which is further subdivided into more focused research fields.

NCERT Class 8 Science Chapter 15 is Some Natural Phenomenon. Natural phenomena such as Lightning and Earthquakes are discussed in class 8 science chapter 15 along with precautions that should be taken to reduce the damage caused by these events. In addition, it features a discussion of many other natural wonders. For example, it covers Lightning's cause, effects, attributes, magnitude, and electroscope operations.

NCERT Solutions does wonders for students who are preparing for their examinations. Extramarks has come up with Class 8 Science Chapter 15 Solutions. These NCERT Solutions of Some Natural Phenomena Class 8 are made exclusively by the experts of Extramarks after thorough research. They try to meet all the requirements of the students.

Extramarks can be a one-stop solution for all students' problems. Apart from NCERT Solutions for Class 8 Science Chapter 15- Some Natural Phenomenon, NCERT Solutions of other subjects, Additional Questions, Sample Papers, Revision Notes, CBSE past years’ question papers, and a lot more can be found on the Extramarks website. 

Key Topics Covered in NCERT Solutions for Class 8 Science Chapter 15

The key topics covered in NCERT SOLUTIONS are enlisted below to make it easier for students.

Introduction to Natural Phenomenon
Static Charges 
Lightning
Earthquakes

 

Let us look at Extramarks' in-depth information on each subtopic in NCERT Solutions for Class 8 Science Chapter 15- Some Natural Phenomena.

Introduction to Natural Phenomenon

Natural phenomena refers to any disaster or physical process that occurs naturally.

Lightning and earthquakes are two natural disasters that NCERT Solutions for Class 8 Science Chapter 15 discusses.

Static Charges 

Any atom, we know, is made up of subatomic particles like electrons, protons, and neutrons. These particles have one thing in common: they have electrical charges. For example, protons have a positive charge, while electrons have a negative charge. Although we know that atoms have a balanced charge, this charge can easily fall out of order. If the proportion of positive and negative charges in an item is balanced, it is termed as electrically neutral.

Methods of Charging:

  • Rubbing which causes friction or induction are the two processes that could charge a body.
  • Static charges are the electrical charges created by rubbing.

Charging by Rubbing

Another important aspect that Extramarks NCERT Solutions for Class 8 Science Chapter 15 explains is Charging by rubbing. When we rub two items together, electrons are transferred between them, and the objects become charged. For example, when we brush a rubber balloon against animal hair, the rubber balloon draws the electrons from the animal fur. As a result, rubber has an overabundance of electrons, whereas fur has an electron deficit. Similarly, we may charge a plastic comb by rubbing it across dry hair.

Charged Objects

Charged objects are items that carry a charge through rubbing or other processes.

Transfer of Charges

Using excellent conductors (metals), charges can be transferred from one conducting substance to another using excellent conductors (metals). The migration of an electron from one atom to another causes charge transfer, states NCERT Solutions for Class 8 Science Chapter 15.

Electroscope

An electroscope is a scientific instrument that can detect the presence of an electric charge on a person's body. The first electroscope with a pivoting needle, dubbed versorium, was created in 1600 by the British physician William Gilbert.

An electroscope on top is made up of a metal detector knob which is then connected to a pair of metal leaves hanging from the bottom of the connecting rod.

The charge is detected using an electroscope using the Coulomb electrostatic force, which causes the test charge to move. Because the electric charge of an item is equal to its capacitance, an electroscope may be used as a primitive voltmeter. The device that measures the charge quantitatively is called an electrometer.

The passage of electrons into or out of the leaves is how an electroscope responds to the presence of a charge. The leaves split in both circumstances. It's vital to remember that the electroscope can't tell if the charged object is positive or negative; it simply looks for an electrical charge.

Discharged  Objects

Discharged objects are those that have lost their charge due to a transfer.

Earthing

Earthing is transferring charges from a charged item to the Earth.

Lightning

Extramarks NCERT Solutions for Class 8 Science Chapter 15 explains the story of Lightning and its aspects in the following section.

Air currents rise upwards during thunderstorms, whereas water droplets fall downwards. This results in charge separation between clouds and the ground.

When the magnitude of charges grows, air (generally a poor conductor) begins to conduct and permits electricity to flow. Lightning is named from the dazzling streaks of light and sound that accompanies the charge movement.

Electric Discharge

An electric discharge is the movement of charge from cloud to cloud or cloud to ground resulting in the separation of positive and negative charges.

Lightning safety steps to follow

Outside the house:

  • Find a secure spot or take refuge under a small tree.
  • Stay inside a car or vehicle with the doors and windows closed.
  • Metal poles should be avoided.
  • Avoid lying on the ground. Crouch with your head between your hands instead.

Inside the house:

  • Contact with telephone and electrical cables should be avoided.
  • Bathe sparingly.
  • Disconnect all electrical appliances.

Lightning Conductors

Lightning conductors help in the protection of structures from Lightning. They are made out of a taller-than-the-building metal rod inserted into the walls during construction. They extend to the ground and serve as a direct path for electric discharge following lightning strikes.

The above section of Extramarks NCERT Solutions for Class 8 Science Chapter 15 explains the story of Lightning and its various aspects. In addition, refer to the Extramarks website to gain more information or study material for all classes.

Earthquakes

Extramarks NCERT Solutions for Class 8 Science Chapter 15 briefly discusses Earthquakes in the following section.

An earthquake is a brief shaking of the ground caused by a movement deep under the surface of the Earth. The four layers that make up the Earth on the inside are called the crust, mantle, outer core, and inner core. The crust comprises many different layers that protect the inner layers. It is fragmented into smaller plates. These plates are constantly moving. Each time they clash or travel above/below each other, they cause a disturbance in the crust. This contact causes an earthquake.

What causes an Earthquake?

Earthquakes get triggered due to tectonic shifts in the Earth's crust. Orogeny occurs when the tectonic plates glide over one another, resulting in tremors and volcanic eruptions. Vibrations spread in all directions due to these disruptions. As the plates move closer together, tension builds up, broken by shock waves, which release the stored energy.

Movement of Plates

Each portion of the Earth's crust is referred to as a plate. These plates are continually moving and can collide under one another, resulting in a surface earthquake.

Fault or Seismic Zones

On the Earth's crust, plate boundaries are weak zones where earthquakes are most prone to occur. They’re called Seismic or fault zones. 

Measuring the strength of the Earthquake

  • An earthquake's strength is measured in magnitude on a scale. The Richter Scale is the name for this scale.
  • A devastating earthquake is one with a Richter magnitude greater than 7.
  • This is not a linear scale. i.e. a two-fold increase in destructive energy equals 1000 times more destructive energy.

Seismic Waves

Seismic waves are created when tremors deep within the ground cause waves.

Seismograph

A device that detects and records the intensity of seismic waves is called a seismograph. When an earthquake occurs, it contains a metal rod or a pendulum that can vibrate. A pen is linked to the metal rod, which records the waves on paper. Scientists examine the waves and then generate an earthquake map. This also aids in determining the magnitude of the Earthquake.

How do you stay safe from an Earthquake?

Outdoors:

  • Find an area that is free of overhead wires and structures.
  • If you're in a car, pull over to a safe area and stay inside until the tremors end.

Indoors:

  • Stay beneath a table until the shaking stops.
  • Stay away from tall, hefty items.

Structural Measures:

  • Build mud buildings with light roofs in seismically active locations to reduce damage.
  • Fix shelves and cupboards to the walls.
  • Some structures catch fire during earthquakes, necessitating suitable firefighting apparatus.

Extramarks NCERT Solutions for Class 8 Science Chapter 15 has discussed the Earthquake and its impacts in the above section. Extramarks provides material that is ready to solve all your doubts and queries. Refer to Extramarks today.

NCERT Solutions for Class 8 Science Chapter 15 Exercise and Solutions

The best way to comprehend all of the concepts of each chapter is to study the NCERT Solutions for that chapter. As a result, Extramarks provides NCERT Solutions for each chapter. Subject experts prepare these Solutions to fulfill all of the needs of the students. Click on the below links to view NCERT Solutions for Class 8 Science Chapter 15:

Class 8 Science Chapter 15: Very Short Answer Type Questions

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Key Features of NCERT Solutions for Class 8 Science Chapter 15

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Q.1 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-

The correct option is (b).

Explanation: Charging by friction is possible only in non-conducting materials. As the copper rod is a conducting material therefore, it cannot be charged by friction.

Q.2 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-

The correct option is (b).”

Explanation: When an object is rubbed with another object, the two objects acquire charges. By convention, it is considered that the charge acquired by the glass rod is positive and charge acquired by the cloth is negative.

Q.3 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 attracts 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
Explanation: Like charges always repel each other while unlike charges attract each other.

(b) True
Explanation: A charged glass rod has positive charges on its surface while a charged plastic straw has negative charges on its surface.

(c) False
Explanation: The lightning conductor transfers all the atmospheric charge to the Earth. Hence, lightning does not affect the building.

(d) False
Explanation: There is no instrument in the world which can predict the earthquake in advance.

Q.3 Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain.

Ans-

The sweater gets charged when it is taken off. It is because of the friction between the sweater and the body. Thus, crackling sound is produced during this process.

Q.5 Explain why a charged body loses its charge if we touch it with our hand.

Ans-

When a person touches a charged object, its charge is conducted by his body to the earth. Hence, the charged body loses its charge.

Q.6 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-

Richter scale is used to measure the destructive energy of an earthquake. This scale has the readings from 1 to 10. Seismograph is used to measure the reading of magnitude 3 on the Richter scale. When Richter scale shows a reading of magnitude 3, the earthquake will not cause much damage. An earthquake of magnitudes higher than 5 is considered destructive in nature.

Q.7 Suggest three measures to protect ourselves from lightning.

Ans-

  1. Keep away from electrical wires, telephone cables, metal pipes, etc.
  2. If you are driving car, then remain there until the lightning is over. Close the windows of the car immediately.
  3. During lighting, do not take bath in running water.

Q.8 Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

Ans-

Two charged balloons have similar nature of charges. As like charges always repel each other hence, two charged balloons will repel each other. When a charged balloon is brought near an uncharged balloon, the uncharged balloon acquires charges on its surface due to induction. Since unlike charges attract each other, a charged body always attracts an uncharged body. Therefore, an uncharged balloon is attracted by another charged balloon.

Q.9 Describe with the help of a diagram an instrument which can be used to detect a charged body.

Ans-

It consists of a metal rod. At one end of the rod, two leaves of aluminium foil are fixed and at the other end, there is a metal disc. The leaves of aluminium foil are placed inside a conical flask and the flask is corked to isolate the leaves from air. When the metal disc is touched with a charged body, the aluminium strips move away from each other. This happens because some of the charges of the body are transferred to the strips through the metal rod. This method of charging a body is called charging by conduction. The nature of charges on both the leaves and the charged body are the similar. Hence, both the leaves of the aluminium foil will move away from each other. If the body was not charged, then the leaves of the foil would remain as they were before. They would not repel each other.

Q.10 List three states in India where earthquakes are more likely to strike.

Ans-

Jammu and Kashmir, Gujarat and Assam are three major states of India where earthquakes are more likely to strike.

Q.11 Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?

Ans-

  1. If you are travelling in a bus or a car, then do not come out when an earthquake strikes.
  2. Rush to find an open field away from tall buildings, installations, tall trees, and electric wires and poles during an earthquake.

Q.12 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-

No, One should not carry an umbrella during thunderstorm. The charge flows from the clouds during thunderstorm,and it can travel through the metallic rod of the umbrella. This may give an electric shock to the person who is carrying it. Thus, it is not safe to carry an umbrella during lightning.

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NCERT answers are provided on the Extramarks website to assist students with examination preparation. These solutions are created by specialists and adhere to the CBSE curriculum. The straightforward language and in-depth explanations of each answer help students grasp the concepts. It clarifies the concepts and allows students to strengthen their fundamental understanding of the chapter. Furthermore, the solutions are precise and to the point, assisting students in improving their preparations.

2. According to the 15th chapter of Science of Class 8th, what are the three destructive Natural Phenomena?

The three most damaging natural disasters are cyclones, earthquakes, and Lightning. They are capable of causing significant damage and displacing human habitats. During those devastating occurrences, human life is also at risk. To save lives and offer humanitarian assistance, appropriate measures must be made to limit the damage caused by natural disasters.