Class 8 Science Chapter 12 Practice Question Answers - Some Natural Phenomena

Q1: What are the two natural calamities?
Ans:

• Lightning and
• Earthquake.

Q2: Name other natural calamities except lightning and earthquake.
Ans: Winds, storms and cyclones.

Q3: Name the two types of charges.
Ans:

• Positive; and
• Negative.

Q4: Mention the interactions of two types of charges.
Ans: Like charges repel each other while unlike charges attract each other.

Q5: Name the device used to protect buildings from lightning.
Ans: Lightning conductor.

Q6: In which direction does the shock waves produced by an earthquake travel?
Ans: Both on the surface and inside the earth.

Q7: What happens when two clouds with unlike charges approach each other?
Ans: Lightning strikes

Q8: Who discovered the static electricity or lightning in clouds and when?
Ans: Benjamin Franklin in 1752.

Q9: Lightning is an __________ on a huge scale.
Ans: electric spark

Q10: The electrical charges generated by rubbing two object is__________ electricity.
Ans: static

Q11: The electrical charges can be transferred from a __________ object to another through a __________ conductor.
Ans: charged, metal

Q12: The crust and mantle is broken into pieces known as __________.
Ans: tectonic plates

Q13: __________ is an instrument that records seismic waves.
Ans: Seismograph

Q14: __________ is the sudden shaking and trembling of the earth.
Ans: Earthquake

Q15: Like charges
(a) attract each other
(b) repel each other
(c) no interaction takes place
(d) none of these
Ans: (b)
Explanation: Like charges, meaning charges that have the same polarity (either both positive or both negative), repel each other due to the electrostatic force. This repulsion is a fundamental principle of electrostatics.

Q16: Earthquake of which magnitude of the following cause the maximum damage?
(a) 3.0
(b) 8.0
(c) 5.0
(d) 4.0
Ans: (b)
Explanation: Earthquakes with higher magnitudes on the Richter scale cause more severe damage. A magnitude of 8.0 or higher indicates a major earthquake that can lead to significant destruction, depending on factors like depth, location, and population density.

Q17: Lightning occurs due to
(a) wind
(b) rain
(c) electric discharge
(d) earthquake
Ans: (c)
Explanation: Lightning occurs due to the discharge of accumulated electrical energy in the atmosphere. This discharge can happen between clouds, from clouds to the ground, or even within a single cloud.

Q18: The shaking and trembling of earth is called
(a) tsunami
(b) volcano
(c) earthquake
(d) none of these
Ans: (c)
Explanation: The shaking and trembling of the Earth's surface caused by the sudden release of energy due to the movement of tectonic plates or other geological processes is known as an earthquake.

Q19: The magnitude of an earthquake is measured ii
(a) Kelvin scale
(b) Celsius scale
(c) Decibel scale
(d) Richter scale
Ans: (d)
Explanation: The magnitude of an earthquake is commonly measured using the Richter scale. The Richter scale quantifies the amount of energy released by an earthquake, providing a logarithmic measure of the earthquake's strength.

Value-Based Questions

Q20: Ms. Neena, Science teacher of class VIII, taught children how to protect themselves and what to do during an earthquake. She even performed an earthquake drill in school for better understanding in children. Children enjoyed this drill and learned a lot from this.

1. What to do during an earthquake if you are stuck indoor?
2. What causes earthquakes?
3. How you must keep yourself ready for an earthquake?
4. What values of Ms. Neena is shown here?

Ans:

1. The following must be done if someone had stuck indoor:
   • Stay away from glass, windows, outside doors and walls.
   • Stay away from anything that could fall such as lightning fixtures or furnitures.
   • Get under a sturdy table/desk, hold it firmly and cover your head.
   • Stay calm and do not panic. Stay inside until shaking stops and it is safe to go outside.
2. Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake.
3. We must keep ourself ready for an earthquake by:
   • Having proper knowledge about do’s and don’ts during an earthquake.
   • Keeping a disaster kit ready in the time of need.
   • Helping needy and injured person after an earthquake.
4. Ms. Neena has future vision, scientific temperament, intelligent, compassionate, caring, dedicated, etc.