Some Natural Phenomena: Question and Answers CBSE/NCERT for Class 8 Science Chapter 15
Questions. Which of the following cannot be charged easily by friction?
Non-conducting materials are frequently easily charged by friction. Because of its high conductivity, copper cannot be easily charged by friction.
Questions: When a glass rod is rubbed with a piece of silk cloth, the rod
A piece of silk cloth rubbed on a glass rod will cause the charge to transfer from the rod to the cloth. The cloth acquires a negative charge, whereas the rod gains a positive charge.
Questions: Write T against true and F against false in the following statements.
False Similar charges repel one another, and opposite charges pull together.
While the glass rod has positive charges on its surface, a charged plastic straw has negative charges. They are attracted to one another since their natures are so different.
A lightning conductor transfers the air charges from the lightning directly to the soil. As a result, the structure is shielded from lighting.
Although the cause of the earthquake is known, no tools have been created to predict them. Because of this, earthquakes cannot be foreseen.
Questions: Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain?
Ans: Our shirts are often composed of cotton coupled with certain synthetic fibres, while our sweater is made of wool. The wool sweater charges up when it is removed from the body because of the friction, and electrons are transferred as the sweater is removed. Thus, throughout this procedure, the cracking sound can be heard.
Questions: Explain why a charged body loses its charge if we touch it with our hand?
Ans: The surplus static charges that are present when we touch a charged body with our hands are discharged via our bodies and into the ground. The charged body becomes neutral as a result of losing its charge.
Questions: 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?
Ans: The Richter Scale is used to gauge an earthquake’s destructive power. The scale reads from one to ten. Seismographs would note the earthquake’s Richter scale magnitude 3 reading. A magnitude 3 earthquake is not anticipated to cause further harm, according to the Richter scale. An earthquake with a magnitude of more than 5 is typically thought to be damaging
Questions: Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
Ans: The balloons have the same kind of surface charge, and since opposite charges repel one another, the two charged balloons are repelled by one another. When a charged balloon is brought close to an uncharged balloon, the opposite charge is induced as a result of the induction. The charged balloon draws the uncharged balloon to it in the same way that opposite charges attract one another.
Questions: List three states in India where earthquakes are more likely to strike?
Ans: The three states with the highest risk of earthquakes are Gujarat, Assam, and Jammu & Kashmir.
Questions: 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.
Ans: No, we shouldn’t have an umbrella with us while it’s storming. When a thunderstorm with lightning occurs, electrical charges could transfer from the cloud to the metal rod of the umbrella, potentially shocking the person holding it. Therefore, carrying an umbrella while it is lighting is not safe.
Questions: Why does lightning strike in a storm between two clouds?
Ans: There may be a highly large discharge between two clouds with opposite charges when they are close to one another. During such a discharge, a significant quantity of energy is released in the form of heat, light, and sound. This is the thunder we hear during a storm and the lightning we see.
Questions: Describe how lightning strikes a tree or building?
Ans: Tall structures and trees can be inductively charged by clouds. As a result, the buildings and trees get the opposite charge. If the charge buildup is very heavy, it will readily pass from a cloud to a building or tree. Due to the enormous amount of energy released, this can be extremely dangerous and cause the building or tree to catch fire.
Questions: What applications does lightning have?
Ans: A great usage for lightning is:
(i)Nitrogen oxides are created when airborne nitrogen and oxygen are combined with the heat and light emitted by lightning. Nitric acid, which falls as rain when it rains, is made when nitrogen oxides are dissolved in water. It is converted into nitrogenous chemicals, which are crucial for plant growth, by the Rhizobium bacteria found in plant roots.
(ii) Ozone can also be created from oxygen thanks to lightning. The ozone in the air prevents the sun’s harmful UV rays from penetrating our bodies.
Questions: Describe the causes of earthquakes?
Ans: Numerous portions of the earth’s crust, known as tectonic plates, are broken up. These plates are moving relative to one another because they are floating over the molten lava below. When plates meet, shift apart, or glide over one another, the resulting vibrations travel to the earth’s surface and are felt as earthquakes.
Questions: Describe three things you’ll do in the event of an earthquake?
Ans: If you are in an earthquake, you should follow these precautions:
(i) Take cover under a table if you are confined to your home or another structure; do not move until the shaking stops. Use your arms to cover your head. Don’t use the elevator.
(ii) Avoid standing close to fans, bookcases, mirrors, hanging plants, or windows.
(iii) Get out of your house or school and go somewhere open.
(iv) If you’re outside, stay clear of tall buildings, trees, signs, poles, and electric poles and wires.
(v) Avoid riding in a car or a bus.
Questions: Define seismic waves, hypocenter, and epicenter?
The Hypocenter, also known as the focus of an earthquake, is the location under the earth’s surface from which the earthquake begins. It frequently lies several kilometres below the surface of the planet. The Epicentre of an earthquake is the location on the surface of the earth just above the hypocenter. Seismic waves, which travel throughout the earth as a result of plate collisions, cause the earth’s surface to vibrate.