CBSE · NCERT · Class 8 Science · Chapter 12

NCERT Solutions: Class 8 Science Chapter 12 - Some Natural Phenomena

12 textbook Q&A12 verifiedFree Content

Chapter-wise NCERT intext questions and exercise answers for Some Natural Phenomena, grounded in the official textbook.

Questions are taken verbatim from the NCERT textbook; answers were grounded against the chapter's content during generation. Items needing review are marked.
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Exercises 12
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1Exercises12 questions
Q.1Which of these cannot be charged easily by friction?v
  1. a. A plastic scale
  2. b. A copper rod
  3. c. An inflated balloon
  4. d. A woollen cloth
Answer:

(b) A copper rod.

Q.2When a glass rod is rubbed with silk cloth, the rodv
  1. a. and cloth both acquire positive charge
  2. b. becomes positively charged while cloth becomes negatively charged
  3. c. and cloth both acquire negative charge
  4. d. becomes negatively charged while cloth becomes positively charged
Answer:

(b) becomes positively charged while the cloth becomes negatively charged.

Q.3Write true or false: like charges attract; charged glass rod attracts charged plastic straw; lightning conductor cannot protect a building; earthquakes can be predicted in advance.v
Answer:

(a) False (b) True, if oppositely charged (c) False (d) False.

Q.4Why is crackling heard while taking off a sweater in winter?v
Answer:

Friction between sweater and body charges them. Discharge of these charges produces tiny sparks and crackling sound.

Q.5Why does a charged body lose charge if touched by hand?v
Answer:

The human body conducts electricity, so charge flows through the body to the earth. This is earthing.

Q.6Name the earthquake scale. If an earthquake measures 3, would a seismograph record it and would it cause much damage?v
Answer:

The Richter scale. A magnitude 3 earthquake is recorded by a seismograph but usually causes little or no damage.

Q.7Suggest three measures to protect ourselves from lightning.v
Answer:

Stay indoors or inside a closed vehicle, avoid open fields and tall trees, and do not use wired phones or touch electrical appliances during a thunderstorm.

Q.8Why is a charged balloon repelled by another charged balloon but an uncharged balloon is attracted?v
Answer:

Two similarly charged balloons repel. A charged balloon induces opposite charge on the nearer side of an uncharged balloon, causing attraction.

Q.9Describe an instrument used to detect a charged body.v
Answer:

A simple electroscope has a metal rod with thin metal leaves. When a charged body touches or comes near the knob, charges spread to the leaves and they diverge, showing charge.

Q.10List three Indian states where earthquakes are more likely.v
Answer:

Jammu and Kashmir, Himachal Pradesh and Assam. Other examples include Uttarakhand and parts of Gujarat.

Q.11What precautions should you take outside during an earthquake?v
Answer:

Move to an open area away from buildings, trees, electric poles and bridges. If in a vehicle, stop in a clear place and stay inside.

Q.12Would you carry an umbrella if a thunderstorm is predicted? Explain.v
Answer:

No. An umbrella with a metal rod can increase the risk of lightning strike in an open area.