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

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.