Some Natural Phenomena Class 8th Physics & Chemistry AP Board Solution

Class 8th Physics & Chemistry AP Board Solution
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  1. Which of the following cannot be charged easily by friction?A. A plastic scale B. A copper…
  2. When a glass rod is rubbed with a piece of silk cloth the rodA. and the cloth both acquire…
  3. Identify True or False sentences among the following: (a) Like charges attract each other…
  4. Sometimes, a crackling sound is heard while taking off sweater during winter. Explain.…
  5. Explain why a charged body loses its charge if we touch it with our hand.…
  6. Name the scale on which the destructive energy of an earthquake is measured. An earthquake…
  7. Suggest three measures to protect ourselves from lightning. .
  8. Explain why a charged balloon is repelled by another charged balloon whereas anuncharged…
  9. List three states in India where earthquakes are more likely to occur. .…
  10. Does your habitation lie in an earthquake prone area? Explain. .
  11. Which place in Andhra Pradesh experiences earthquakes most of the time? .…
  12. When does a piece of matter have a “charge?”
  13. What happens if two objects having the same charge are brought close to each other? What…
  14. Give two examples of effects in your daily life which are caused by transfer of charges.…
  15. Inflate two balloons and rub both of them with a cloth first and then with different…
  16. Which country in the world is frequently effected by earth quakes? Collect the information…
  17. Find out if there is an organization in your area which provides relief to those suffering…
  18. How do you relate the energy release during the collision of fault lines during earthquake…
  19. Describe with the help of a diagram an instrument which can be used to detect a charged…
  20. Color seismic zones in India out line map. .
  21. Prepare a model of seismograph.
  22. How do you appreciate the efforts of scientists to develop an instrument to measurethe…
  23. Suppose you are outside your home and an earthquake occurs. What precaution would you take…
  24. The weather department has predicted that a thunderstorm is likely to occur on a certain…
  25. If earthquake occurs in your area what will you do? .
  26. What are the measures you would take in your house when an earthquake occurs?…

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Question 1.

Which of the following cannot be charged easily by friction?
A. A plastic scale

B. A copper rod

C. An inflated balloon

D. A woollen cloth

E. Piece of wood


Answer:

Only non-conducting materials can be charged by friction


Option (a) Plastic is non-conducting material hence it can be easily charged by friction.


Option (b) Copper is conducting material hence copper rod cannot be easily charged by friction. Therefore, it is the correct option


Option (c) Balloon is non-conducting material hence it can be easily charged by friction.


Option (d) Wool is non-conducting material hence it can be easily charged by friction.


Option (e) Wood is non-conducting material hence it can be easily charged by friction.


Question 2.

When a glass rod is rubbed with a piece of silk cloth the rod
A. and the cloth both acquire positive charge.

B. becomes positively charged while the cloth has a negative charge.

C. and the cloth both acquire negative charge.

D. Becomes negatively charged while the cloth has a positive charge.


Answer:

Option (a) when an object is charged by rubbing it against another object the two objects gets oppositely charged. Hence the same charge cannot be there on both rod and the cloth.


Option (b) by convention, it is considered that the charge acquired by the glass rod is positive and charge acquired by cloth is negative. Therefore, the rod becomes positively charged while the cloth has a negative charge. Hence (b) option is correct.


Option (c) when an object is charged by rubbing it against another object the two objects gets oppositely charged. Hence the same charge cannot be there on both rod and the cloth.


Option (d) by convention, it is considered that the charge acquired by the glass rod is positive and charge acquired by cloth is negative. Hence this option is not correct.


Question 3.

Identify True or False sentences among the following:

(a) Like charges attract each other (T/F)

(b) A charged glass rod attract a charged plastic straw (T/F)

(c) Lightning conductor cannot protect a building from lightning (T/F)

(d) Earthquakes can be predicted in advance (T/F)


Answer:

(a) False


Like charges repel each other and unlike charges attract each other.


(b) True


A charged glass rod has positive charge on its surface while the charged plastic straw has negative charge on its surface. And unlike charges attract each other therefore the above statement is true.


(c) False


During a lightning, the lightning conductor conducts all the atmospheric charges to the earth directly, leaving the building safe. Hence, the lightning conductor protect a building from lightning.


(d) False


The reason for the earthquake can be known, but no instrument could be invented to detect it till now. Hence, earthquakes cannot be predicted in advance.



Question 4.

Sometimes, a crackling sound is heard while taking off sweater during winter. Explain.


Answer:

The crackling sound is heard due to electric discharge between sweater and body. The sweater is made up of wool and the shirt we wear is made up of cotton blended with some synthetic fibers. When we take out the sweater the friction is developed and the transfer of electrons take place from shirt to sweater, this results in building of electric potential.

When enough potential has been accumulated while taking of the sweater it discharges and transfer of electrons take place. This transfer of electrons forms spark and let out sound energy and heat energy. Thus we hear the crackling sound and in dark room we may see the spark lights as well.



Question 5.

Explain why a charged body loses its charge if we touch it with our hand.


Answer:

When we touch a charged object our body conducts its charges to the earth because our body is the conductor of electricity. Therefore a charged body loses its charge if we touch it with our hand. This phenomenon is called as electric discharge.



Question 6.

Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?


Answer:

The destructive energy of earthquake is measured on the Richter scale, this scale is not linear and it has readings from 1 to 10.

The reading of 3 would be recorded by a seismograph. But the earthquake is not likely to cause much damage because generally the earthquake of measure higher than 5 are considered destructive in nature.



Question 7.

Suggest three measures to protect ourselves from lightning. .


Answer:

Protective measures against lighting are as follows.

1. Stay indoors or in completely closed place. If you are moving in the car than remain there until the lighting is over.



2. Do not touch any conductor of electricity like electric wires, telephone cables, metal pipes etc.


3. Do not take shelter under tree because you may get an electric shock due to water present on leaves of tree which will conduct electricity.



4. Switching off and disconnecting all heavy electrical appliances like Television, Air conditioner etc.



Question 8.

Explain why a charged balloon is repelled by another charged balloon whereas anuncharged balloon is attracted by a charged balloon?


Answer:

The nature of the charges present on the surface of the charged balloon is same, Since the like charges repel each other. Therefore the two charged balloons repel each other. As shown in the figure below.


When the charged balloon is brought near the uncharged balloon, the uncharged balloon acquires the charge opposite to the charge of charged balloon and we know that unlike charges repel each other. Therefore the uncharged balloon is attracted by a charged balloon. As shown in the figure below.




Question 9.

List three states in India where earthquakes are more likely to occur. .


Answer:

The three states in India where the earthquakes are more likely to occur are:

1. Jammu and Kashmir Major earthquake occurred on 8th


October2005 in Uri and Tangdhar towns of North Kashmir.


2. Gujarat Here Major earthquake occurred on 26th January 2001. In Bhuj District of Gujarat.



3. Assam in 1897 a devastating earthquake occurred which measured 7.1 on Richter scale.



Question 10.

Does your habitation lie in an earthquake prone area? Explain. .


Answer:

I live in Madhya Pradesh and it is not an earthquake prone area because as we can see in the Map below which describes the earthquake prone areas in India. The Madhya Pradesh which is at center of India is in Low risk zone – II and Moderate risk zone – III.