Class 8 Science
Natural Phenomena
NCERT Solution
Question 1: Which of the following cannot be charged easily by friction?
- A plastic scale
- A copper rod
- An inflated balloon
- A woollen cloth
Answer: (b) A copper rod
Question 2: When a glass rod is rubbed with a piece of silk cloth the rod
- and the cloth both acquire positive charge.
- becomes positively charged while the cloth has a negative charge.
- and the cloth both acquire negative charge.
- becomes negatively charged while the cloth has a positive charge.
Answer: (b) becomes positively charged while the cloth has a negative charge.
Question 3: Write T against true and F against false in the following statements:
- Like charges attract each other
- A charged glass rod attract a charged plastic straw
- Lightning conductor cannot protect a building from lightning
- Earthquakes can be predicted in advance
Answer: (a) F, (b) T, (c) F, (d) F
Question 4: Sometime, a crackling sound is heard while taking off sweater during winters. Explain.
Anwer: When a sweater is taken off, it gets charged because of rubbing. Due to this, we get to hear a crackling sound.
Question 5: Explain why a charged body loses its charge if we touch it with our hand.
Anwer: When a charged body is touched by hand, the human body provides a passage for the charge to the earth. Due to this, the charged body loses its charge.
Question 6: 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?
Anwer: The destructive energy of an earthquake is measured on Richter scale. An earthquake which measures 3 on this scale would be recorded by a seismograph. An earthquake of this intensity is not likely to cause any damage.
Question 7: Suggest three measures to protect ourselves from lightning.
Anwer: Three measures to protect from lightning are as follows:
- Try to remain indoors.
- Do not carry an umbrella during lightning.
- If in open; do not take shelter under a tall tree or any tall structure.
Question 8: Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
Anwer: When both the balloons carry similar charges, they are repelled by each other. But a charged balloon attracts an uncharged balloon because a charge object has a tendency to attract an uncharged object.
Question 9: Describe with the help of a diagram an instrument which can be used to detect a charged body.
Anwer: Structure of Electroscope: It is made of a glass jar. A vertical brass rod is inserted into the jar through a cork. The top of the brass rod has a horizontal brass rod or a brass disc. Two gold leaves are suspended from the brass rod; inside the jar.
Question 10: List three states in India where earthquakes are more likely to strike.
Anwer: Jammu & Kashmir, Himachal Pradesh and Uttarakhand
Question 11: Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?
Anwer: If we are out in the open and an earthquake strikes, we can take following precautions:
- Try to move away from buildings and other structures.
- If you are in a vehicle, ask the driver to take the vehicle far from buildings.
- Keep away from bridges.
Question 12: 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.
Anwer: If a thunderstorm is being predicted then we should not carry an umbrella. The metallic handle of an umbrella can be a potential target for lightning and it is unsafe to carry an umbrella.