Worksheet solutions for chapter: Some Natural Phenomena for class 8 are provided below.
(1) What is lightning?
Ans-
Lightning in cloud is accumulation of charges in the clouds and produces heat which vibrates and expands the air of surrounding. As the result of it we can hear thunder sound after a flash of light.
(2) Why earthing of buildings is necessary?
Ans-
The process of transferring of charge from a charged object to the earth is called earthing.
Eg:- Leakage of electric current passes through to earth.
(3) If you are in forest and a thunderstorm strikes. What will you do to save yourself?
Ans-
If I am in forest and a thunderstorm strikes I will take shelter under small trees. Lightening always find nearest and shortest path to flow to ground. So, tall trees are the nearest and shortest path for electricity to reach ground. Trees are good conductor of electricity. Therefore, it can be possible that electricity will go through the trunk and branches may fall down. Electricity will flow through you if you are sitting under the tree.
(4) How earthquakes occur?
Ans-
The earth has four layers, crust, mantle, outer core and inner core. Crust is the outer most layer. It is fragmented in seven plates. These plates slide. When they collide or brush past each other, cause disturbance in the earth’s crust. It is called earthquake.
(5) Draw the structure of the earth.
Ans-
(6) What precautions should be taken against earthquake at the time of building construction?
Ans-
The precautions should be taken against earthquake at the time of building constructions.
(i) Consult qualified architects and structural engineers.
(ii) Use mud and timber is good in construction. Roof of the house should be of light material. It will cause less damage.
(iii) Fix cupboards and shelves on the walls.
(iv) Building should have fire extinguishers. It will be very helpful if buildings catch fire at e time of earthquake.
(7) After viewing diagram complete the sentence.
The balloon and plastic rod have _____________ charge because they _____.
Ans-
The balloon and plastic rod have opposite charge because they attract each other.
(8) What instructions will you give to carpenter if you are living in seismic zone?
Ans-
I will instruct him to fix all cupboard and shelves with the walls. Therefore, they will not fall down at the time of earthquake and cause less damage.
(9) Show by a diagram that same charged objects repel each other.
Ans–
(10) Fill in the blanks
(i) The destructive earthquakes have magnitudes higher than ___ on the Richter scale.
(ii) _____ is an instrument which is used by the scientists to record seismic waves.
(iii) The process of transferring of charge from a charged object to the earth is called _____.
Ans-
(i) The destructive earthquakes have magnitudes higher than 7 on the Richter scale.
(ii) Seismograph is an instrument which is used by the scientists to record seismic waves.
(iii) The process of transferring of charge from a charged object to the earth is called earthing.
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