Multiple Choice Questions.....................
Question 1: An electroscope is a device which is used to find if an object is
(a) charged
(b) magnetic
(c) free of cracks
(d) hot
Solution 1: (a) charged
An electroscope is a device that decides whether or not an object is charged. It is made up of two closely spaced metallic strips.
Question 2: 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
Solution 2: (c) copper wire
Copper is an excellent electrical conductor. Plastic, rubber, and cotton are poor electrical conductors.
Question 3: The movement of the earth’s plates causes
(a) cyclones
(b) lightning
(c) earthquakes
(d) thunderstorms
Solution 3: (c) earthquakes
Earthquakes occur as the earth's plates brush against one another. Buildings and dams may be affected by the earth.
Question 4: 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
Solution 4: (c) they may attract or repel depending on the type of charges they carry
If the charges are similar, they repel each other, while if they are dissimilar, they attract each other.
Question 5: Which of the following is not likely to cause Tsunami?
(a) A major nuclear explosion undersea
(b) Earthquake
(c) Volcanic eruption
(d) Lightning
Solution 5: (d) Lightning
Tsunamis are caused by a disruption deep under the surface of the water. Lightening will not disrupt the sea, but earthquakes, massive nuclear explosions under the sea, and volcanic eruptions can.
Question 6: 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
Solution 6: (a) the crust of the earth
The earth trembles or shakes suddenly as a result of a movement deep within its top layer, known as the crust.
Question 7: 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)
Solution 7: (a) (i) & (ii)
An earthquake is a sudden trembling or shaking of the earth that lasts just a few seconds. Plate tectonics are responsible for earthquakes. Plate boundaries are vulnerable areas where earthquakes are most likely to happen.
Question 8: The outermost layer of earth is called
(a) mantle
(b) outer core
(c) crust
(d) inner core
Solution 8: (c) crust
The crust is the top layer of the Earth, followed by the mantle, outer core, and inner core.
Question 9: Major earthquakes are less likely to occur in
(a) North East India
(b) Rajasthan
(c) Rann of Kutch
(d) Orissa
Solution 9: (d) Orissa
In Orissa, major earthquakes are less likely to occur. Kashmir, the Western and Central Himalayas, the entire North-East, the Rann of Kutch, Rajasthan, and the Indo-Gangetic Plain are the most threatened areas in India.
Question 10: 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)
Solution 10: (a) (i), (ii) & (iii)
Earthquakes can cause Tsunami, Landslide and Floods.
Very Short Answer Questions.................................
Question 11: 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.
Solution 11:
(a) True
(b) True
(c) True
(d) False- Electric discharge takes place between clouds and the earth.
(e) True
Question 12: Is it possible to predict the occurrence of an earthquake?
Solution 12: No, it is difficult to guess when an earthquake would strike.
Question 13: If a charged plastic straw is brought near another uncharged plastic straw, what will happen?
Solution 13: If a charged plastic straw is brought near another uncharged plastic straw then plastic straws will attract one another.
Question 14: The aluminium strips in an electroscope as shown in given figure are replaced by plastic strips and a charged body is brought in contact with the metal clip. What will happen?
Solution 14: If the aluminium strips in an electroscope as shown in given figure are replaced by plastic strips and a charged body is brought in contact with the metal clip then there will be no divergence of strips.
Question 15: Plastic straws A and B are rubbed with a dry cotton cloth. What will happen if they are brought near each other?
Solution 15: Plastic straws A and B are rubbed with a dry cotton cloth. They will repel each other if they are brought near.
Short Answer Questions.................................
Question 16: 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.
Solution 16: It won't work because the charge won't get through to the ground because the lightning conductor isn't wired properly to the ground.
Question 17: If air and cloud were good conductors of electricity, do you think lightning could occur? Explain.
Solution 17: No, lightning would not strike because the isolation of charges in conductors is impossible. As a result, charges will not settle on clouds, and lightning will not occur.
Question 18: Identify the lightning conductor and the copper plate in Fig. 15.2.
Solution 18: The lightning conductor is A
The copper plate is B
Question 19: 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?
Solution 19: If the materials used to construct a building are good conductors, no installing conductor is needed.
Question 20: You might have observed on a dry day that when you touch the screen of a television or computer monitor (with a picture tube), you get a slight shock. Why does it happen?
Solution 20: On the screen, the electric charge builds up. A charge is discharged from our body when we hit the screen. As a result, we are given a mild shock.
Question 21: Explain how does lightning conductor protect a building from getting struck by lightning.
Solution 21: The charge is carried to the earth by the lightning conductor, so it will not collect on the structure. This keeps the building safe from lightning strikes.
Question 22: 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?
Solution 22: If the electroscopic clip comes into contact with a positively charged object, the previously negative charges will be neutralised, and the strips will collapse.
Question 23: 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.
Solution 23: When we touch strips of electroscope with our hand, the charge in the strips is discharged through our hand, and the strips return to their original state.
Long Answer Questions....................
Question 24: Explain how lightning takes place?
Solution 24: The air currents travel upwards as a thunderstorm forms, while the water droplets move downwards. The separation of charges is triggered by the rapid movement of air currents. Positive charges accumulate near the clouds' upper edges, while negative charges accumulate near the clouds' lower edges. Positive charges have accumulated above the ground as well. When the magnitude of the cumulative charges exceeds a certain threshold, the air becomes unable to withstand their flow. As a result, negative and positive charges collide, resulting in a blinding flash of light and sound known as lightning.
Question 25: Mention three precautions that you will take to protect yourself if an earthquake strikes when you are inside the house.
Solution 25:
- When you're in bed, don't get out of it. Using a pillow to cover your head.
- Take cover under a table and wait for the shaking to end.
- Maintain a safe distance from tall and large items that might fall on you.
Question 26: Explain why it is safer to use a wireless telephone instead of a landline telephone during lightning.
Solution 26: Electrical discharge is the mechanism that induces lightning. Electric charge can pass through landline telephone wires during lightning, which is dangerous. As a result, it is better to use a cell phone rather than a landline phone during a lightning storm.
Question 27: What precautions would you take if lightning occurs while you are outside the house?
Solution 27:
- If it's raining, don't bring an umbrella.
- Keep a safe distance from poles and other metallic artefacts.
- Avoid open vehicles such as motorcycles, tractors, building equipment, and open automobiles.
- Get low to the ground and squat. Place your hands on your knees and your head in the space between them.
- Do not seek refuge in open fields, tall trees, park shelters, or elevated locations.
Question 28: 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.
Solution 28: If the electroscope's metal clip is replaced with an ebonite rod and a charged body is put in contact with it, aluminium strips will not repel. Since ebonite is an insulator, no charge will be transferred to it.