Q: What causes static electricity in clothes?
A: Static electricity in clothes is caused by friction between different materials, particularly when taking off woolen or polyester clothes, which can result in charge accumulation.
Q: Why should you avoid bathing during a thunderstorm?
A: Bathing should be avoided during thunderstorms because water is a good conductor of electricity, and running water can carry electrical charge if lightning strikes nearby.
Q: What are the two destructive natural phenomena discussed in the chapter?
A: Lightning and earthquakes.
Q: What did ancient Greeks discover about amber around 600 B.C.?
A: They discovered that when amber (a kind of resin) was rubbed with fur, it attracted light objects such as hair.
Q: What happens when two charged balloons are brought near each other?
A: They repel each other because they have the same kind of charge.
Q: What happens when a charged balloon is brought near a charged refill?
A: They attract each other because they have different kinds of charges.
Q: What are static charges?
A: Electrical charges generated by rubbing that do not move by themselves are called static charges.
Q: What is an electroscope and how does it work?
A: An electroscope is a device used to detect whether an object is charged. It consists of aluminum foil strips that repel each other when charged with the same type of charge.
Q: What is earthing?
A: Earthing is the process of transferring charge from a charged object to the earth through a conductor.
Q: How are charges separated in clouds during a thunderstorm?
A: During thunderstorms, air currents move upward while water droplets move downward. These movements cause separation of charges, with positive charges collecting near upper edges and negative charges near lower edges of clouds.
Q: What causes lightning?
A: Lightning occurs when the magnitude of accumulated charges becomes very large and negative and positive charges meet, producing streaks of bright light and sound.
Q: What are three safety measures to be taken during lightning when outside?
A:
Stay away from tall trees
Do not lie on the ground
Squat low on the ground with hands on knees and head between hands
Q: What precautions should be taken inside the house during a thunderstorm?
A:
Avoid contact with telephone cords, electrical wires, and metal pipes
Avoid bathing
Unplug electrical appliances like computers and TVs
Q: What is a lightning conductor?
A: It’s a metallic rod taller than the building, installed with one end in the air and the other buried in the ground, providing an easy route for charge transfer during lightning.
Q: What causes earthquakes?
A: Earthquakes are caused by disturbances deep inside the earth’s crust, usually due to movement of earth’s plates.
Q: What are earth’s plates?
A: The outermost layer of earth (crust) is fragmented, and each fragment is called a plate. These plates are in continual motion.
Q: What are seismic or fault zones?
A: These are weak zones at the boundaries of plates where earthquakes are more likely to occur.
Q: Name three areas in India that fall in the earthquake danger zone.
A: Kashmir, Western and Central Himalayas, and the whole of North-East.
Q: What is the Richter scale used for?
A: The Richter scale is used to express the power (magnitude) of an earthquake.
Q: What magnitude on the Richter scale indicates a really destructive earthquake?
A: Earthquakes with magnitudes higher than 7 on the Richter scale are really destructive.
Q: What building materials are recommended in highly seismic areas?
A: The use of mud or timber is better than heavy construction materials, and roofs should be kept as light as possible.
Q: What should you do if you are in bed during an earthquake?
A: Stay in bed and protect your head with a pillow.
Q: What should you do if you are in a car during an earthquake?
A: Stay in the car and ask the driver to drive slowly to a clear spot. Don’t come out till the tremors stop.
