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Ncert Exemplar Solutions Class 8 Science Some Natural Phenomena
Welcome to NCTB Solutions. Here with this post we are going to help 8th class students for the Solutions of NCERT Exemplar Class 8 Science Book, Unit 15, Some Natural Phenomena. Here students can easily find step by step solutions of all the problems for Some Natural Phenomena, Also here our Science teacher’s are solved all the questions with easily understandable language with proper guidance so that all the students can understand easily.
Some Natural Phenomena all Question Solutions :
Multiple Choice Questions :
Question no – (1)
An electroscope is a device which is used to find if an object is
Answer :
The correct answer is option – (a)
An electroscope is a device which is used to find if an object is Charged.
Question no – (2)
Electric current is to be passed from one body to another. For this purpose the two bodies must be joined by
Answer :
Correct option – (c)
For this purpose the two bodies must be joined by Copper wire.
Question no – (3)
The movement of the earth’s plates causes
Answer :
Correct option – (c)
The movement of the earth’s plates causes Earthquakes.
Question no – (4)
Two charged objects are brought close to each other. Choose the most appropriate statement from the following options:
Answer :
Correct option – (c)
The most appropriate statement – they may attract or repel depending on the type of charges they carry.
Question no – (5)
Which of the following is not likely to cause Tsunami?
Answer :
Correct option – (d)
Lightning is not likely to cause Tsunami.
Question no – (6)
The earth’s plate responsible for causing earthquakes is
Answer :
Correct option – (a)
The earth’s plate responsible for causing earthquakes is the crust of the earth.
Question no – (7)
Consider the list of terms given below :
Answer :
Correct option – (a) (i) and (ii)
The boundaries of the earth’s plate are known as Seismic Zone or Mantle.
Question no – (8)
The outermost layer of earth is called
Answer :
Correct option – (c)
The outermost layer of earth is called Crust.
Question no – (9)
Major earthquakes are less likely to occur in
Answer :
Correct option – (d)
Major earthquakes are less likely to occur in Orissa.
Question no – (10)
Consider the list of terms given below
Answer :
Correct option – (a) (i), (ii) and (iii)
Earthquakes can cause (i) Tsunami, (ii) Landslide and (iii) Floods.
Very Short Answer Questions :
Question no – (11)
Answer :
(a) Earthquakes occur all the time all over the world.
= This statement is True.
(b) The plates of the outermost layer of the earth are always in continuous motion.
= This statement is True.
(c) Tremors on the earth can also be caused by the eruption of a volcano.
= This statement is True.
(d) The process of electric discharge cannot occur between clouds and the earth.
= This statement is False
Reason : The process of electric discharge occurs between the earth and the clouds in the form of lightning.
(e) Bathing outdoors should be avoided during thunderstorm.
= This statement is True.
Question no – (12)
Answer :
It is very hard even for scientists to accurately predict the timing and place of an earthquake.
Question no – (13)
Answer :
When the two straws are brought close towards each other the charged straw will attract the uncharged straw because it usual for charged items to attract other uncharged items of same kind.
Question no – (14)
Answer :
The Aluminium strip is replaced by the plastic strips and since plastic is not a good conductor of electricity, so it will not receive any charge from the paper clip. The plastic strips will not show any movement like the Aluminium strips so it will very difficult to predict whether the object is charged or not.
Question no – (15)
Answer :
When the straw A and B are rubbed with a dry cotton cloth they will gain the same type of charge and so the straws will repel each other.
Short Answer Questions :
Question no – (16)
Answer :
A lighting conductor must be connected to the ground by means of a copper plate buried deep into the ground in order for it to work. So if it is kept hanging in the air without joining it to the ground it will a useless installment.
No, the lightning conductor would not be effective at all. The metal conductor should be properly connected to the ground via a long metallic rod dug deep into the ground. After the proper installment then and only then the conductor would work.
Question no – (17)
Answer :
If air and cloud were good conductors of electricity then the electric all charges would not accumulate in the ground and the clouds as the charges would easily flow between them, so this will not result in a charge accumulation and so no lighting will happen.
Question no – (19)
Answer :
If the building were made of conducting materials then the charges that need to be accumulated in the buildings would travel between the charged objects. So the building itself will act as a lightning conductor and so the magnitude of charge will remain insufficient and no lighting would occur.
Question no – (20)
Answer :
The phenomenon simply happens because during dry day the television or monitor accumulate static charges so when we touch the screen of these appliances the charges travel through our fingers, so we face a little shock.
Question no – (21)
Answer :
The role of a lightning conductor is to prevent lighting strike on it by preventing the accumulation of a charge on the buildings by conducting all the charges to the ground via means of a long rod connecting the conductor and the ground.
Question no – (22)
Answer :
If a positively charged object comes in contact with the an electroscope then the metal clip which were in diverged position due to the negative charge will now contract due to neutralization from the positive charge.
Question no – (23)
Answer :
As we touch the strips with our bare hand then the charges on the strip will travel through our hand and into the ground which will then result into the contraction of the metal strips.
Long Answer Questions :
Question no – (24)
Answer :
During a thunderstorm air current moves up while the water droplets moves downward. This movement causes a charge separation between the clouds and the ground. So when the charge separation became so high in nature that even air which is a bad conductor of electricity can’t even prevent the flow of charge. So when the charges meet they produce a streak of lightning with an explosive sound and light.
Question no – (25)
Answer :
The three precautions that I will take at home during time of an earthquake are :
• I would protect my head with a pillow if I am on the bed.
• I would stay away from tall and heavy objects like almirah that could fall on me.
• I would get under a hard object such as bed and a table till the earthquake stops.
Question no – (26)
Answer :
It is safer to use a wireless phone than a wired one because during a lightning strike electrical wires, metal pipes and telephone cords often discharge electricity whereas wireless phone are in no way coming in contact with an electrical wire so it is much safer.
Question no – (27)
Answer :
We should take the following precautions outside during time of a lightning strike :
• We should not take shelter under an umbrella.
• We should not take shelter under a tall object like trees, poles or stay in an open area or an elevated place.
• If we are stuck in an open field we should squat with our knees bent and head between the hands instead of lying down.
• We should not take shelter inside a car, bike, tractor or a construction machinery as they are not safe at all.
Question no – (28)
Answer :
If the metal clip used in the electroscope is replaced by an ebonite rod there would be no effect in the aluminum strips as it is known that ebonite is a poor conductor of electricity so it won’t carry a charge at all if it comes it contact with a charged object. As a result it won’t transfer a charge to the aluminum strips and hence we would not be able to observe any repulsion in the strips.
Other Chapter Solutions :
👉 Crop Production and Management
👉 Microorganisms : Friend and Foe
👉 Synthetic Fibres and Plastics
👉 Materials : Metals and Non-Metals
👉 Conservation of Plants and Animals
👉 Cell-Structure and Functions
👉 Reaching the Age of Adolescence
👉 Force
👉 Friction
👉 Sound
👉 Chemical Effects of Electric Current
👉 Light
