## Topic outline

• ### Some Natural Phenomena

##### Q1. Fill in the blanks.

i.        The plates of earth's crust are in continual motion.

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

iii.        In an electroscope, the aluminium leaves diverge because like charges repel.

iv.        Earthing is provided in buildings to protect us from electrical shocks due to any leakage of electrical current.

v.        Lightning is also an electric spark, but on a huge scale.

vi.        The outermost layer of the earth is not in one piece. It is fragmented. Each fragment is called a plate.

##### Q2. State True (T) or False (F).

i.        Like charges attract each other. F

ii.        A charged glass rod attract a charged plastic straw. T

iii.        Lightning conductor cannot protect a building from lightning. F

iv.        Earthquakes can be predicted in advance. F

v.        An earthquake of magnitude 6 has thousand times more destructive energy than an earthquake of magnitude 4. T

vi.        Earthquakes tend to occur at the boundaries of earth’s plates. T

##### Q3. List three states in India where earthquakes are more likely to strike.

Ans. Gujarat, Kashmir, Rajasthan

##### Q4. How will you charge a glass rod by the method of friction?

Ans. A glass rod can be charged by rubbing it with silk cloth.

##### Q5. What are the two kinds of electric charges?

Ans. There are two kinds of charges — positive charge and negative charge.

##### Q6. What is a flash of light which occurs in the sky during the rainy season called?

Ans. Lightning

##### Q7. How a ballpoint pen refill can be charged by the method of friction?

Ans. A ballpoint pen refill can be charged by rubbing it against the woolen cloth.

##### Q8. What are the three layers of earth?

Ans. Earth can be divided into three main layers: the core, the mantle and the crust.

##### Q9. What happens when two like charges are brought together?

Ans. When two like charges are brought together then they will repel each other.

##### Q10. What is the purpose of the Richter scale?

Ans. The Richter scale is used to measure the magnitude (or intensity) of an earthquake.

##### Q11. What is directly below the epicenter of an earthquake?

Ans. Focus of an earthquake is located below the epicenter of an earthquake.

##### Q12. What kind of electric charge is acquired by a plastic comb rubbed with dry hair?

Ans. The plastic comb acquires negative charge when it is rubbed with dry hair.

##### Q13. How an inflated rubber balloon can be charged by the method of friction?

Ans. An inflated balloon can be charged by rubbing it against the woolen cloth.

##### Q14. What is focus of an earthquake?

Ans. The place inside the earth’s crust where the earthquake begins is called focus of an earthquake.

##### Q15. What is the instrument used to measure and record an earthquake?

Ans. Seismograph is the instrument which is used to measure and record an earthquake.

##### Q16. What is epicentre of an earthquake?

Ans. The point on the earth’s surface directly above the focus is called epicentre of an earthquake.

##### Q17. What type of electric charge is acquired by a rubber balloon when rubbed with a woolen cloth?

Ans. When balloon is rubbed with a woolen cloth, it acquires negative electric charge.