CBSE Class 8 Science Chapter 15: Some Natural Phenomena NCERT Solutions

Reviewed by · Updated on

NCERT Solutions PDF Class 8 PDF

This chapter delves into the fascinating world of natural phenomena, focusing on static electricity, lightning, and earthquakes. Students will explore how objects get charged through friction, the behavior of electric charges, and the principles behind lightning conductors. The solutions also cover the measurement of earthquake intensity using the Richter scale and provide essential safety measures to protect oneself during thunderstorms and lightning strikes. Understanding these concepts is crucial for grasping basic physics principles and ensuring safety in natural disasters. These NCERT Solutions offer clear explanations and step-by-step answers to help students prepare effectively for their exams by reinforcing their understanding of the chapter's key topics.

Home

Quick info

BoardCBSE
ClassClass 8
SubjectScience
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 15

Chapter summary

Chapter 15 of the CBSE Class 8 Science syllabus focuses on 'Some Natural Phenomena.' This section provides NCERT Solutions that explain the concepts of static electricity, including charging by friction and the attraction/repulsion of charges. It also covers lightning, its causes, and protection methods like lightning conductors. Additionally, the chapter introduces earthquakes, their measurement on the Richter scale, and safety precautions. The solutions aim to clarify these topics with straightforward explanations.

Learning outcomes

  • Understand the process of charging objects through friction.
  • Differentiate between conductors and insulators regarding electrical charge.
  • Explain the attraction and repulsion between electric charges.
  • Describe the phenomenon of lightning and the function of a lightning conductor.
  • Identify the scale used to measure earthquake intensity.
  • List safety measures to take during lightning and thunderstorms.

Topics covered

Paper topics

  • Charging by Friction
  • Conductors and Insulators
  • Electric Charges
  • Attraction and Repulsion
  • Static Electricity
  • Lightning
  • Lightning Conductors
  • Earthquakes
  • Richter Scale
  • Safety Measures

Important topics

  • Charging by Friction
  • Attraction and Repulsion of Charges
  • Lightning and its Protection
  • Earthquake Measurement (Richter Scale)
  • Safety Precautions

PDF preview

Read page by page below. PDF is streamed from the official NCERT website — no download button on this page.

Loading document …
Page of
Loading page …

Questions and Solutions

Question 1

Which of the following materials cannot be easily charged by friction?

(a) A plastic scale

(b) A copper rod

(c) An inflated balloon

(d) A woollen cloth.

Solution: The correct option is (b) A copper rod. Materials like plastic scales, inflated balloons, and woollen cloths are insulators. Insulators do not allow electric charges to flow through them easily, so they can be charged by friction. A copper rod, however, is a conductor. Conductors allow electric charges to flow through them readily, meaning any charge applied by friction would quickly dissipate, making it difficult to charge easily by this method.

Question 2

When a glass rod is rubbed with a piece of silk cloth, what happens?

(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: The correct option is (b) becomes positively charged while the cloth has a negative charge. When a glass rod is rubbed with silk, electrons are transferred from the glass rod to the silk cloth. Since electrons are negatively charged, the glass rod loses electrons and becomes positively charged. The silk cloth gains these electrons and becomes negatively charged. This process demonstrates charging by friction.

Question 3

State whether the following statements are True (T) or False (F):

(a) Like charges attract each other

(T/F)

(b) A charged glass rod attracts a charged plastic straw

(T/F)

(c) A lightning conductor cannot protect a building from lightning

(T/F)

(d) Earthquakes can be predicted in advance

(T/F)

Solution:

(a) Like charges attract each other (False)

Explanation: Like charges, such as two positive charges or two negative charges, repel each other. Unlike charges, such as a positive and a negative charge, attract each other.

(b) A charged glass rod attracts a charged plastic straw (True)

Explanation: A glass rod rubbed with silk becomes positively charged. If a plastic straw is charged negatively (e.g., by rubbing with wool), then the positively charged glass rod will attract the negatively charged plastic straw.

(c) A lightning conductor cannot protect a building from lightning (False)

Explanation: A lightning conductor is specifically designed to protect buildings from lightning by providing a safe path for the electric current to flow into the ground.

(d) Earthquakes can be predicted in advance (False)

Explanation: Currently, earthquakes cannot be predicted accurately in advance. While scientists can monitor seismic activity, predicting the exact time, location, and magnitude of an earthquake remains a significant challenge.

Question 4

Sometime, a crackling sound is heard while taking off a sweater during winters. Explain why this happens.
Solution: During winter, sweaters are often made of wool, and the inner clothes might be made of synthetic fibres or cotton. When you wear a sweater, friction occurs between the wool fibres of the sweater and the fibres of your inner clothing, as well as between the sweater and your skin. This friction causes a transfer of electrons, leading to the accumulation of static electric charges on the surface of the sweater. When you take off the sweater, especially in dry conditions, the accumulated charges can suddenly discharge through the air between the sweater and your body or the surroundings. This rapid discharge of electricity creates small sparks and the audible crackling sound you hear.

Question 5

Explain why a charged body loses its charge if we touch it with our hand.
Solution: The human body is a relatively good conductor of electricity. When you touch a charged body with your hand, you provide a path for the excess electric charges on the body to flow. These charges transfer from the charged body, through your body, and into the Earth. This process is called earthing or grounding. Since the Earth can absorb a large amount of charge without significantly changing its electrical potential, the charged body loses its accumulated charge, becoming neutral.

Question 6

Name the scale on which the destructive energy of an earthquake is measured. If an earthquake measures 3 on this scale, would it be recorded by a seismograph? Is it likely to cause much damage?
Solution: The scale on which the destructive energy of an earthquake is measured is called the Richter Scale. Yes, an earthquake measuring 3 on the Richter Scale would definitely be recorded by a seismograph. Seismographs are sensitive instruments designed to detect even very small vibrations in the Earth's crust. However, an earthquake of magnitude 3 is considered to be of low intensity. It is unlikely to cause significant damage to buildings or structures and might only be felt as a slight tremor by people in the immediate vicinity.

Question 7

Suggest three measures to protect ourselves from lightning.
Solution: Here are three measures to protect ourselves from lightning:
  1. Seek Safe Shelter: During a thunderstorm, the safest place to be is inside a substantial building, such as a house or a large office building, or inside a hard-top vehicle. Avoid small, open structures like sheds or tents, and stay away from tall, isolated objects like trees.
  2. Avoid Water and Metal: Do not take a bath or shower, wash dishes, or do any activity involving contact with water during a thunderstorm, as water conducts electricity. Also, stay away from metal objects like pipes, radiators, and electrical appliances, as they can conduct electricity.
  3. Stay Indoors and Wait: Once you are in a safe shelter, remain there for at least 30 minutes after the last thunderclap. Thunderstorms can produce lightning even after the rain has stopped or when the storm appears to be moving away.

Common mistakes

  • Confusing attraction with repulsion between charges.
  • Incorrectly identifying conductors and insulators.
  • Underestimating the danger of lightning and not taking adequate safety measures.
  • Misunderstanding the Richter scale's measurement of earthquake intensity.

Revision tips

  • Review the definitions of conductors and insulators.
  • Memorize the rules for attraction and repulsion of charges.
  • Understand the working principle of a lightning conductor.
  • Note down the safety precautions for lightning and earthquakes.
  • Practice identifying true/false statements related to electrical charges and natural phenomena.

Practice MCQs

Q1. Which of the following materials cannot be easily charged by friction?

Q2. When a glass rod is rubbed with silk, what happens to the charges?

Q3. Which statement about electric charges is FALSE?

Q4. What is the primary function of a lightning conductor?

Q5. The destructive energy of an earthquake is measured on which scale?

Frequently asked questions

What is static electricity?

Static electricity is the accumulation of electric charge on the surface of an object. It is often produced by friction, such as rubbing a balloon on hair.

Why do we hear a crackling sound when taking off a sweater in winter?

This sound is due to static discharge. Friction between the sweater and your body causes charges to build up. When you remove the sweater, these charges jump between the sweater and your body, creating sparks and a crackling sound.

What is the difference between a conductor and an insulator?

A conductor allows electric charges to flow through it easily (like metals), while an insulator resists the flow of electric charges (like plastic or rubber).

How does a lightning conductor protect a building?

A lightning conductor provides a low-resistance path for the electric charge from a lightning strike to travel safely into the ground, preventing damage to the building.

What does a reading of 3 on the Richter scale indicate?

A reading of 3 on the Richter scale indicates a minor earthquake. It can be detected by a seismograph but is unlikely to cause significant damage.

What are the essential safety measures during a thunderstorm?

During a thunderstorm, it is safest to stay indoors, away from windows and metal objects. If outdoors, seek shelter in a substantial building or a vehicle, and avoid open fields or tall isolated trees.

Important links

Content reviewed by the NCERT Help team. Editorial Team and update policy

NCERT Solutions PDF PDF on NCERT Help. URL unchanged for search indexing.