Ncert solutions science class 8 Solutions for Chapter 15 some natural phenomena

Q1) 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.

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.

An electroscope is a device which is used to find if an object is

(a)charged

(b)magnetic

(c)free of cracks

(d)hot

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

Q2) When a glass rod is rubbed with a piece of silk cloth the rod:-

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.

The movement of the earth’s plates causes

(a)cyclones

(b)lightning

(c)earthquakes

(d)thunderstorms

Q3) Write T against true and F against false in the following statements:

(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)

Write T against true and F against false in the following statements.

(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)

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

Q4) Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain.

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

Q5) Explain why a charged body loses its charge if we touch it with our hand.

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

Which of the following is not likely to cause Tsunami?

(a)A major nuclear explosion undersea

(b)Earthquake

(c)Volcanic eruption

(d)Lightning

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?

Q6) 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?

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

Suggest three measures to protect ourselves from lightning

Q7) Suggest three measures to protect ourselves from lightning.

Consider the list of terms given below:

(i)Seismic Zone

(ii)Fault Zone

(iii)Mantle

(iv)Inner Core

The boundaries of the earth’s plate are known as

(a)(i) & (ii)

(b)(i) & (iii)

(c)(iii) & (iv)

(d)(ii), (iii) & (iv)

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

Q8) Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

The outermost layer of earth is called

(a)mantle

(b)outer core

(c)crust

(d)inner core

Q9) Describe with the help of a diagram an instrument that can be used to detect a charged body

Major earthquakes are less likely to occur in

(a)North East India

(b)Rajasthan

(c)Rann of Kutch

(d)Orissa

Describe with the help of a diagram an instrument which can be used to detect a charged body.

Q10) List three states in India where earthquakes are more likely to strike.

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

Consider the list of terms given below

(i)Tsunami

(ii)Landslide

(iii)Floods

(iv)Lightning

Earthquakes can cause

(a)(i), (ii) & (iii)

(b)(ii) & (iv)

(c)(ii), (iii) & (iv)

(d)(iii) & (iv)

Q11) Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?

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 a thunderstorm.

Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?

Q12) 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.

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.

Is it possible to predict the occurrence of an earthquake?

If a charged plastic straw is brought near another uncharged plastic straw, what will happen?

The aluminium strips in an electroscope as shown in fig. are replaced by plastic strips and a charged body is brought in contact with the metal clip. What will happen?

Plastic straws A and B are rubbed with a dry cotton cloth. What will happen if they are brought near each other?

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.

If air and cloud were good conductors of electricity, do you think lightning could occur? Explain.

Identify the lightning conductor and the copper plate in Fig.

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?

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?

Explain how does lightning conductor protect a building from getting struck by lightning.

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 an equal amount of positive charge is brought in contact with the clip, what will happen?

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.

Explain how lightning takes place?

Mention three precautions that you will take to protect yourself if an earthquake strikes when you are inside the house.

Explain why it is safer to use a wireless telephone instead of a landline telephone during lightning.

What precautions would you take if lightning occurs while you are outside the house?

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.