Q1Multiple choice
An electroscope is a device which is used to find if an object is
- (a)charged
- (b)magnetic
- (c)free of cracks
- (d)hot
Show answer
(a) charged
Chapter 15 – Some Natural Phenomena
Class 8 Science · 28 questions · 28 with answers
Questions
Q2Multiple choice
Electric current is to be passed from one body to another. For this purpose the two bodies must be joined by
- (a)cotton thread
- (b)plastic string
- (c)copper wire
- (d)rubber band
Show answer
(c) copper wire
Q3Multiple choice
The movement of the earth’s plates causes
- (a)cyclones
- (b)lightning
- (c)earthquakes
- (d)thunderstorms
Show answer
(c) earthquakes
Q4Multiple choice
Two charged objects are brought close to each other. Choose the most appropriate statement from the following options:
- (a)they may attract
- (b)they may repel
- (c)they may attract or repel depending on the type of charges they carry
- (d)there will be no effect
Show answer
(c) they may attract or repel depending on the type of charges they carry
Q5Multiple choice
Which of the following is not likely to cause Tsunami?
- (a)A major nuclear explosion under sea
- (b)Earthquake
- (c)Volcanic eruption
- (d)Lightning
Show answer
(d) Lightning
Q6Multiple choice
The earth’s plate responsible for causing earthquakes is
- (a)the crust of the earth
- (b)the mantle of the earth
- (c)the inner core of the earth
- (d)the outer core of the earth
Show answer
(a) the crust of the earth
Q7Multiple choice
Consider the list of terms given below: (i) Seismic Zone (iii) Mantle (ii) Fault Zone (iv) Inner Core S OME NATURAL PHENOMENA 87 The boundaries of the earth’s plate are known as
- (a)(i) & (ii)
- (b)(i) & (iii)
- (c)(iii) & (iv)
- (d)(ii), (iii) & (iv)
Show answer
(a) (i) & (ii)
Q8Multiple choice
The outermost layer of earth is called
- (a)mantle
- (b)outer core
- (c)crust
- (d)inner core
Show answer
(c) crust
Q9Multiple choice
Major earthquakes are less likely to occur in
- (a)North East India
- (b)Rajasthan
- (c)Rann of Kutch
- (d)Orissa
Show answer
(d) Orissa
Q10Multiple choice
Consider the list of terms given below (i) Tsunami (iii) Floods (ii) Landslide (iv) Lightning Earthquakes can cause
- (a)(i), (ii) & (iii)
- (b)(ii) & (iv)
- (c)(ii), (iii) & (iv)
- (d)(iii) & (iv)
Show answer
(a) (i), (ii) & (iii)
Q11Multiple choice
State whether the following are True or False.
- (a)Earthquakes occur all the time all over the world.
- (b)The plates of the outermost layer of the earth are always in continuous motion.
- (c)Tremors on the earth can also be caused by the eruption of a volcano.
- (d)The process of electric discharge cannot occur between clouds and the earth. (e) Bathing outdoors should be avoided during thunderstorm.
Show answer
(a) Earthquakes occur all the time all over the world.
(b) The plates of the outermost layer of the earth are always in continuous motion.
(c) Tremors on the earth can also be caused by the eruption of a volcano.
(d) The process of electric discharge cannot occur between clouds and the earth. (e) Bathing outdoors should be avoided during thunderstorm.
Q12Very short answer
Is it possible to predict the occurrence of an earthquake?
Show answer
No
Q13Very short answer
If a charged plastic straw is brought near another uncharged plastic straw, what will happen?
Show answer
The two will attract each other.
Q14Very short answer
The aluminium strips in an electroscope as shown in fig. 15.1 are replaced by plastic strips and a charged body is brought in contact with the metal clip. What will happen? 88 E XEMPLAR PROBLEMS Fig. 15.1
This question refers to a figure in the original PDF.
Show answer
No divergence of strips will take place.
Q15Very short answer
Plastic straws A and B are rubbed with dry cotton cloth. What will happen if they are brought near each other?
Show answer
They will repel each other. SHORT ANSWER QUESTIONS
Q16Short answer
During the construction of a building the lightning conductor was left hanging in the air by mistake. Would the lightning conductor be still effective? Explain.
Show answer
No, it will not be effective. Since lightning conductor was not connected properly to the earth, therefore, the charge will not pass through to the earth.
Q17Short answer
If air and cloud were good conductors of electricity, do you think lightning could occur? Explain.
Show answer
No, it will not occur. The charge separation cannot take place in conductors. Therefore charges will not accumulate on clouds and so lightning cannot take place.
Q18Short answer
Identify the lightning conductor and the copper plate in Fig. 15.2. Fig. 15.2 S OME NATURAL PHENOMENA 89
This question refers to a figure in the original PDF.
Show answer
A is the lightning conductor and B is the copper plate.
Q19Short answer
If the materials used for constructing a building were good conductors, do you think lightning will strike the building. Will the lightning conductor be still required to be installed in the building?
Show answer
No. There is no need to install lightning conductor in the building.
Q20Short answer
You might have observed on a dry day that when you touch the screen of a television or computer monitor (with picture tube), you get a slight shock. Why does it happen?
Show answer
Electric charge gets accumulated on the screen. On touching the screen the charge discharges through our body. Thus, we get a slight shock.
Q21Short answer
Explain how does lightning conductor protects a building from getting struck by lightning.
Show answer
Lightning conductor does not allow the charge to accumulate on a building as it conducts the charge to the earth, protecting building from being struck by lightning. 148 E XEMPLAR PROBLEMS
Q22Short answer
In an electroscope if a negatively charged body is brought in contact with the metal clip, the strips of the electroscope diverge. If now another charged object carrying equal amount of prositive charge is brought in contact with the clip, what will happen?
Show answer
If a positively charged object is brought in contact with the clip of an electroscope, the negative charge given earlier will be neutralised and the strips will collapse.
Q23Short answer
The strips of an electroscope diverge when a charged body is brought in contact with the metal clip. Now the clip is touched gently by our hand. What will happen to the strips? Explain.
Show answer
The charge that was in the electroscope strips will get discharged through our hand. The strips will come back to the original state. LONG ANSWER QUESTIONS
Q24Long answer
Explain how lightning takes place?
Show answer
During the development of a thunderstorm, the air currents move upwards while the water droplets move downwards. These vigorous movements of air currents cause separation of charges. The positive charges collect near the upper edges of the clouds and the negative charges accumulate near the lower edges. There is accumulation of positive charges near the ground also. When the magnitude of the accumulated charges become large, the air cannot resist their flow. As a result negative and positive charges meet producing a streak of bright light and sound, called lightning.
Q25Long answer
Mention three precautions that you will take to protect yourself if earthquake strikes when you are inside the house.
Show answer
(i) Take shelter under a table and stay there till the shaking stops. (ii) Stay away from tall and heavy objects that may fall on you. (iii) If you are in bed, do not get up. Protect your head with a pillow. (If a child gives any other reasonable precautions, it should be accepted)
Q26Long answer
Explain why it is safer to use a wireless telephone instead of a landline telephone during lightning.
Show answer
Lightning is an electrical discharge. During lightning atmospheric electric charge may discharge through landline telephone wires and may become dangerous. Therefore it is safer to use a wireless telephone instead of a landline telephone during lightning.
Q27Long answer
What precautions would you take if lightning occurs while you are outside the house?
Show answer
(i) Stay away from poles or other metallic objects. (ii) Stay away from tall trees. (iii) Stay away from open vehicles like motorbikes, tractors, construction machinery etc. (If a child gives any other reasonable precautions, it should be accepted)
Q28Long answer
If the metal clip used in the electroscope is replaced by an ebonite rod and a charged body is brought in contact with it, will there be any effect on the aluminium strips? Explain.
Show answer
The aluminium strips will not show any repulsion. The charged body will not transfer any charge to the ebonite rod as ebonite rod is an insulator. As a result there will be no charge on the aluminium strips and no repulsion will occur. ANSWERS 149