Class 8 Exam  >  Class 8 Notes  >  Science Class 8  >  Short Notes - Some Natural Phenomena

Some Natural Phenomena Class 8 Notes Science Chapter 12

Introduction and Lightning

Lightning is a natural event that has intrigued humans for a long time. Many have studied what causes lightning and how it occurs. Benjamin Franklin discovered that there is an electric discharge between clouds that creates a spark. This electric spark between the clouds and the ground is what we see as lightning. His famous kite experiment demonstrated this concept. 
Here is how lightning occurs:

  • The formation of clouds happens when water vapour in the atmosphere condenses.
  • This condensation charges the particles within the clouds.
  • Negative charges gather at the bottom of the cloud, while positive charges accumulate at the top.
  • The increasing charge in the cloud generates a positive charge on the ground nearby.
  • As the charge builds up, the negative charge from the cloud seeks a path to the ground, creating what we know as lightning.

An Electroscope

Some Natural Phenomena Class 8 Notes Science Chapter 12

Question for Short Notes - Some Natural Phenomena
Try yourself:
What did Benjamin Franklin's kite experiment prove about lightning?
View Solution

An electroscope is a device that detects the type of charge on a body. Like charges repel and unlike charges attract each other. This is used in an electroscope. An electroscope consists of a glass jar fitted with a cork lid and a metallic wire passing through it. There are two metallic strips at the bottom of the wire. The upper end of the wire is connected to a metal disc. A body that is positively charged is touched to the metal disc, so that the charge is transferred to the metal strips through the wire, and they diverge from each other on gaining a like charge. Now, if a negatively charged object is brought into contact with the disc, the strips converge towards each other, indicating the unlike charge on the body. Similarly, if a positively charged body is brought in contact with the metal disc, the divergence of the metal strips increases, indicating the like charge on the body. If the metal disc of the electroscope is touched with the hand, it loses its charge to the ground by transfer of charge through the human body. This is called earthing.

Some Natural Phenomena Class 8 Notes Science Chapter 12

Lightning and Safety

Lightning results from the build-up of charges in clouds and can cause significant damage to life and property. Therefore, it is crucial to take protective measures during lightning storms. Safe places to seek shelter from lightning include:

  • Staying indoors and avoiding open areas.
  • Not sheltering under trees or in open spaces if outside.
  • If in a vehicle, remaining inside and keeping doors and windows closed.
  • Tall buildings often have lightning rods, which are metal rods on the roofs connected to a thick copper wire buried underground. If lightning strikes, it is attracted to the rod, allowing the electrical discharge to be transferred safely to the ground.
  • The weather department can provide warnings about developing thunderstorms.

Earthquakes

Some Natural Phenomena Class 8 Notes Science Chapter 12

  • A natural phenomenon that cannot be predicted is an earthquake. The earth consists of three major layers, called the crust, the mantle and the core. The core is further divided into the inner core and the outer core. 
  • The mantle consists of semi-solid material above which the crust floats. The crust consists of oceans and continents. The crust is divided into several parts, called tectonic plates. The regions where one tectonic plate slides against another are referred to as fault zones, and these are the regions where an earthquake is likely to occur. Hence, these zones are referred to as seismic zones.
  • The place in the interior of the earth where an earthquake occurs is the focus, and the region on the surface of the earth that is the closest to focus is likely to experience the largest damage. This region is called the epicentre of the earthquake.

Question for Short Notes - Some Natural Phenomena
Try yourself:
What is the purpose of a lightning rod on a tall building?
View Solution

  • The instrument that measures the severity of an earthquake is a seismograph. It basically consists of a drum that rolls and a pendulum with a stylus that traces the waves of an earthquake on a sheet like a graph paper. The severity of an earthquake is measured on the Richter scale. A major earthquake measures 7 or more on the Richter scale.
     

The document Some Natural Phenomena Class 8 Notes Science Chapter 12 is a part of the Class 8 Course Science Class 8.
All you need of Class 8 at this link: Class 8
Are you preparing for Class 8 Exam? Then you should check out the best video lectures, notes, free mock test series, crash course and much more provided by EduRev. You also get your detailed analysis and report cards along with 24x7 doubt solving for you to excel in Class 8 exam. So join EduRev now and revolutionise the way you learn!
Sign up for Free Download App for Free
93 videos|278 docs|44 tests

Up next

FAQs on Some Natural Phenomena Class 8 Notes Science Chapter 12

1. What are natural phenomena?
Ans. Natural phenomena are the events that occur naturally in the environment and are not man-made. Some examples of natural phenomena are lightning, earthquakes, tornadoes, hurricanes, and volcanic eruptions.
2. What causes lightning?
Ans. Lightning is caused by the buildup of electrical charges in the atmosphere. When there is a difference in electrical charge between the ground and the atmosphere, a lightning bolt can be formed to neutralize the charge.
3. How are earthquakes caused?
Ans. Earthquakes are caused by the sudden movement of tectonic plates, which are the large pieces of the Earth's crust that float on the surface of the planet. When these plates move, they can create shockwaves that can be felt as an earthquake.
4. Can natural phenomena be predicted?
Ans. Some natural phenomena can be predicted, while others cannot. For example, scientists can use weather patterns and other data to predict hurricanes and tornadoes, but earthquakes and volcanic eruptions are much more difficult to predict.
5. Why is it important to study natural phenomena?
Ans. It is important to study natural phenomena because it helps us to better understand the world around us and how it works. By studying natural phenomena, we can learn about the forces that shape the planet and the impact that humans have on the environment. This knowledge can help us to better protect ourselves and the planet.
93 videos|278 docs|44 tests
Download as PDF

Up next

Explore Courses for Class 8 exam
Related Searches

Sample Paper

,

shortcuts and tricks

,

video lectures

,

Summary

,

Some Natural Phenomena Class 8 Notes Science Chapter 12

,

Some Natural Phenomena Class 8 Notes Science Chapter 12

,

Exam

,

Free

,

Some Natural Phenomena Class 8 Notes Science Chapter 12

,

Extra Questions

,

Important questions

,

practice quizzes

,

ppt

,

Previous Year Questions with Solutions

,

MCQs

,

Objective type Questions

,

Semester Notes

,

Viva Questions

,

pdf

,

past year papers

,

study material

,

mock tests for examination

;