Lakhmir Singh Manjit Kaur Class 8 Science 15th Chapter Some Natural Phenomena Solution

Lakhmir Singh and Manjit Kaur Science solution: Some Natural Phenomena Chapter 15. Here you get easy solutions of Lakhmir Singh and Manjit Kaur Science solution Chapter 15 . Here we give Chapter 15 all solution of Class 8. Its help you to complete your homework.

• Board – CBSE
• Text Book – SCIENCE
• Class – 8
• Chapter – 15.

VERY SHORT ANSWER TYPE QUESTIONS :

(1.)  Positive and negative.

(2.) a> Positive, b> Negative

3.) Negative.

4.) Positive charge.

5.) Positive charge.

6.) Negative charge.

7.) a> Negative, b> Positive.

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8.) a> Positive,  b> negative

9.) Electroscope.

10.) Object has electric charge on it.

11.) Lightning.

12.) The light can hit in the tree.

13.) Benjamin Franklin.

14.) Lightning conductor.

15.) Earthquake

17.) Kashmir, western and central Himalayas, the whole of North-East.

18.) Seismograph.

19.)  7.7 on richter scale.

20.)  Richter scale.

21.) To watch The magnitude of an earthquake.

22.) Tsunami, Volcanic eruption.

23.) Focus

24.) (a) False (b) True (c) False (d) False (e) True (f) True (g) False

25.) (a) repel; attract (b) positive (c) negative (d) electrons (e) friction (f) repel (g) earthing (h) electric (i) plate

SHORT ANSWER TYPE QUESTIONS :

26.) When we rub the plastic comb with our dry hair, the plastic comb gets electric charge due to friction. The electrically charged comb then exerts an electric force on the tiny pieces of paper and attracts them.

27.) By using silk cloth.

28.) By using a woolen cloth we i charge a inflated rubber balloon by the method of friction.

29.) With the friction of hair or friction of woolen cloth.

30.) The friction of two ball pen refill can charge two ball pen refill.

31.)  Electroscope will show that the negative charge on the meter.

32.) Electroscope will show that the negative charge on the meter. The plastic comb gets electric charge due to friction.

33.) An electroscope collapse as soon as we touch the metal cap with hand because the leaves of the charged electroscope lose charge to the earth through our body.

34.)  When we touch a charged object, our body conducts its charges to the earth. That is why a charged body loses its charge, if we touch it with our hand.

35.) It will be turned into Earthquake.

36.) Earthquake.

37.) With the help of electroscope.

38.) It might be dangerous because lighting may strike the top end of the metal rod of umbrella.

39.) The person should place his hand on his knees with his head between the hands. This position will make the make the person the shortest object around which is unlikely to be hit by lightning.

40.) Three measures are :

• We should avoid raising an umbrella over the head during lightning.
• The TV antennas and dish antennas fixed on tall buildings are especially prone to lightning areas.
• Lightning can strike metal pipes. Fixed in buildings. So, during a thunderstorms when lighting is taking place, we should avoid touching the metal pipes fixed in a house or buildings.

42.) a> Thick strip of metal.

b> Spike.

c> Highest point of the building.

d> Buried deep in the  ground near the building.

43.) The precautions are :

• We should take shelter under a sturdy table or a kitchen counter
• We should stay away from tall and heavy objects
• If we are in bed, we should just move on the bed to be close to a wall but not get up from the bed.

44.) The precautions are :

• We should stay at a clear spot away from buildings, trees and over-head power lines etc.
• If we are in a car, we should not come out of it. The car or bus should be driven slowly.

LONG ANSWER TYPE QUESTIONS :

46.) The electroscope is a device for detecting charge on an object.

Working of electroscope: 

47.) (a) The bright flash of light which we see in the clouds is called lightning.

Lightning is an electric discharge in the atmospheric between oppositely charged clouds.

(b) Objects on the ground have very little influence on its travelling path, until the stroke comes to a distance very close to the ground. That’s why lightning usually strike tall buildings.

(c) when lightning strikes the earth,it can be cause a lot of destruction by damaging property, tress and killing people.

48.) (a) If lightning strikes, it will hit the top of the lightning conductor. The electric energy of lightning passes through the metal strip and gets dischargesd safely into the ground through the buried metal plate.

The lightning conductor was invented by Benjamin Franklin.

(b) Lightning strikes are more frequent in the hilly areas because such areas clouds are comparatively closer to the ground.

49.) Earthquake is a destructive natural phenomenon which cannot be predicted is advance.

Two main situations are : a> Slide past one another.

b> Collide with one another.

(b) The place inside the earth crust where the earthquake is generated, is called focus

The point on earth’s surface directly above the focus is called epicenter.

50.) Three layers of earth are : Core, Mantle, Crust.

Seismograph is an instrument which measures and records the magnitude of an earthquake in terms of the shock waves it produces.

Higher Order Thinking Skills (HOTS)

71) Two inflated balloons are hanged near each other. Both of them were rubbed using a woolen cloth. Now both the balloons are charged with similar charges. We can see that both the balloons are repelling each other. We know that the same charge particle repel each other, that is the reason when two balloons charged with same charge kept near each other repel each other. On the other hand if only one of the balloons is charged with woolen clothes and the other is kept uncharged then we can see the balloons attracting each other. In this case the charge particles on the charged balloon will produce opposite charges on the uncharged balloon by electric induction. We know that opposite charge attracts each other. That is the reason why when one charged and one uncharged balloon kept near each other they attract one another.

72)

A glass rod can be charged through rubbing when held in hand because glass rod is an insulator which does not conduct electric charges produced on its surface through our hand and body into the earth.

On the other hand an iron rod cannot be charged by rubbing when held in hand because when held in hand because iron rod is a conductor due to which as soon as it gets charged by rubbing, the electric charges produced on its surface flow through our hand and body into the earth and it remains uncharged.

73)

When two objects are rubbed together, then both the objects get charged by friction but with opposite charges. Whether an object will lose electron and acquire positive charge or the gain electron and acquire negative charge depends on the nature of the material of the object. Now if a glass rod is rubbed with a silk cloth, then the glass rod will loose electron and acquire positive charge and silk cloth will acquire negative charge by gaining electrons. When an inflated balloon is rubbed with a woolen cloth then the woollen cloth will acquire positive charge by losing electrons and the inflated balloon will acquire negative charge by gaining electrons.

74)

The Electroscope is a device for detecting electric charge on an object. By using electroscope we can tell whether an object is electrically charged or not.

The electroscope detects the presence of charge in any object. It cannot differentiate between whether the charge on that object is positive or negative. When the metal top of an electroscope is touched with positivelycharged object then the aluminium leaves of the electroscope diverge or open up. Similarly if the metal top of an electroscope is touched with negatively charged object then the aluminium leaves of the electroscope diverge or open up.

75)

Seismograph is an instrument which measures and records the magnitude of an earthquake in terms of the shock waves it produces. The Richter scale is used to express the magnitude or intensity of an earthquake from a scale 1 to 12.An earthquake that is measured 3 on Richter scale will definitely be recorded by a seismograph. An earthquake of magnitude 3 will be felt by us however not likely to cause any serious damage.

For more Chapter solution, click below

• Chapter 1) Crop Production And Management
• Chapter 2) Micro Organisms : Friend And Foe
• Chapter 3) Synthetic Fibres And Plastics
• Chapter 4) Materials : Metals And Non-Metals
• Chapter 5) Coal And Petroleum
• Chapter 6) Combustion And Flame
• Chapter 7) Conservation Of Plants And Animals
• Chapter 8) Cell Structure And Functions
• Chapter 9) Reproduction In Animals
• Chapter 10) Reaching The Age Of Adolescence
• Chapter 11) Force And Pressure
• Chapter 12) Friction
• Chapter 13) Sound
• Chapter 14) Chemical Effects Of Electric Current
• Chapter 16) Light
• Chapter 17) Stars And The Solar System
• Chapter 18) Pollution Of Air And Water