Class-8 Science Chapter-15 Some Natural Phenomina

         EVENTS CONVENT H.SCHOOL

05/02/2021             CLASS-8                   SLOT-2
Science
Chapter-15 Some Natural Phenomina

_______________________________________

MCQs

Question 1.Like charges when brought near each other then they

(a) repel (√)

(b) attract

(c) sometimes attract and sometimes repel

(d) have no effect

 

Question 2.A device used to test the charge on an object is called

(a) ammeter

(b) electroscope  (√)

(c) seismograph

(d) none of these

 

Question 3.A major earthquake occurred on 8th October 2005 in

(a) Gujarat

(b) Delhi

(c) Haryana

(d) North Kashmir  (√)

 

Question 4.A sudden shaking of the earth lasting for a very short time is known as □

(a) lightning

(b) thunder

(c) earthquake  (√)

(d) Tsunami

 

Question 5.A major Tsunami occurred in the Indian Ocean on

(a) 26th December 2001

(b) 26th December 2002

(c) 26th December 2003

(d) 26th December 2004  (√)

 

Question 6.Instrument used to find the source of seismic waves is known as

(a) seismometer  (√)

(b) voltammeter

(c) galvanometer

(d) ammeter

 

Question 7.Richter scale is used to measure the magnitude of

(a) lightning

(b) charges

(c) earthquake  (√)

(d) rainfall

  

Very Short Questions and Answers:-

Question 1.Why do two charge bodies attract or repel ? [NCT2008]

Answer:When the two bodies have the same charges, they repel each other and when the two bodies have different charges they attract each other.

 

Question 2.Write the one name of method by which object can be charged. 

Answer:Object can be charged by conduction.

 

Question 3.Which of the following cannot be charged easily by friction ? 

 1.A plastic scale.

2.A copper rod. (√)

3.An inflated balloon.

4.A woollen cloth.

 

Question 4.When a glass rod is rubbed with a piece of silk cloth the rod and the cloth both acquire positive charge.

1.becomes positively charged while the cloth has a negative charge. (√)

2.and the cloth both acquire negative charge.

3.becomes negatively charged while the cloth has a positive charge

 

Question 5.Tick T for true and F for false in the following statements : 

1.     Like charges attract each other. (False)

2.    A charged glass rod attract a charged plastic straw. (True)

3.    Lightning conductor cannot protect a building from lightning. (False)

4.    Earthquakes can be predicated in advance. (False)

Question 6.Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain. 

Answer:This crackling sound is heared because due to friction between the hair and sweater the sweater gets charged.

 Question 7.What is meant by earthing ?

Answer:The process of transfer of charges from a charged object to the earth is called earthing.

 Question 8.When does a body become discharged ?

Answer:When a body looses its charges, it is said to be discharged.

Short Questions and Answers

Question 1.Explain why a charged body loses its charge if we touch it with our hand.

Answer:When we touch a charged body with our hand, the body is earthed. This causes the charges flow to the earth and the body looses the charge.

 

Question 2.List three states in India where earthquakes are more likely to strike. 

Answer:Three states in India where earthquakes can occur are Gujarat, Rajasthan and Jammu & Kashmir.

 

Question 3.The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella ? Explain. 

Answer:No, I would not carry an umbrella. The charges produced during a thunderstrom can flow through the umbrella and harm us.

 

Question 4.When a charged plastic straw is brought near a charged plastic straw, there is repulsion between them. What type of charge exists between them ?

Answer:The charge on both the plastic straw are same, since like charges repel each other.

 

Question 5.When a charged balloon is brought near a charged refill, there is attraction between the two. What type of charge exists between the two ?

Answer:The charge on the balloon and a refill are different, because unlike charges attract each other.

 

Question 6.Why is the charging by rubbing known as static electricity ?

Answer:Charging by rubbing is known as static electricity because the charges do not move.

Long Questions and Answers

Question 1.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 the earthquake can be measured on the Richter scale. Yes, an earthquake measuring 3 would be recorded by the seismograph. This earthquake would not cause much damage.

 

Question 2.Suggest three measures to protect ourselves from lightning. [

Answer:We can protect ourselves from lightning by

switching off and disconnecting all heavy electrical appliances.

Not bathing under running tap water.

Not standing near metallic poles.

 

Question 3.Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon ? 

Answer:A charged balloon has the same charge as another charged balloon, so there is repulsion between them because like charges repel each other. On the other hand, an uncharged body always attracts a charged body. Therefore, an uncharged balloon is attracted by a charged balloon.

 

Question 4.Apart from disturbance inside the earth, what are the other reasons of earthquake ?

Answer:Earthquakes can also occur due to underground nuclear explosion, or when a volcano erupts, or when a meteor hits the earth.

Question 5.What are weak zones ?

Answer:Since earthquakes are caused by the movements of plates, the boundaries of the plates are weak zones where earthquakes are most likely to occur.