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GURUKUL CENTRAL ACADMY, CH.- 15- some natural, phenomena, WORKSHEET-1, Refer text book, WORKSHEET-2, A. 1. Conduction 2. Seismic waves 3. Magma 4. Focus, 5. Volcanic eruptions, movement of tectonic plates, 6. Benjamin Franklin, B. Do’s — 4 5 6, C. 1. T 2. F 3.F, , Don’ts — 1 2 3, 4. T 5.T, , TEXTBOOK EXERCISES, Page 167 Try These, 1. F 2. T 3. T 4. F 5. T, Page 170 Try These, 1. conductor, 2. Lightning 3. repel, 4. glass, wood 5. detect, , EXERCISES, A. 1. a., B. 1., , 2. d., , Seismic, 2. Richter scale, 3. earthing, , 3. d. 4. c., , 5. b. 6. c.

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GURUKUL CENTRAL ACADMY, 4. Open space, 5. Richter, C. 1. T, 2. F, , 3. F, , 4. T, , 5. T, , 6. T, , D. 1., , Thunder, 2. All over the earth, 3. Positive charge, 4. Crust, mantle, core, 5. Conductors, , E. 1., , 2., , Building and trees may fall and injure us., , The process of transferring of charge from a charged object to the, earth is known as earthing., Waves which originate when the plates in the surface of the earth, collide with each other are called seismic waves., The intensity of earthquake is maximum at places which are located, on the boundaries of two plates. These weak zones are known as, seismic zones., , Northeast Kashmir, parts of Rajasthan, Rann of Kutch and the IndoGangetic plain, ., 4. Tsunamis are huge and powerful waves of water which travel at a, great speed., 3., , 5., , An electric charge is a physical quantity which is responsible for the, electrostatic force of attraction or repulsion between matter., Generally in a substance, the number of protons and the electrons, is the same. Therefore, the substance is electrically neutral. But, when two objects are rubbed, the balance may get disturbed. One of

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GURUKUL CENTRAL ACADMY, the objects loses some electrons. Now it has more of protons, and, hence becomes positively charged. The object which gains becomes, negatively charged., 6. • During lightning and thunderstorm, open spaces are most unsafe., Take cover immediately., • Look for a large, enclosed building for shelter. Avoid small sheds, and pavilions. Do not stand under a tree., • If you are in a car or a bus, stay inside and keep the windows, rolled up. Do not stay close to any metal object., , F., , 7., , A lightning conductor is a device installed in a tall building to, protect the building from the effect of lightning. It consists of a, thick metal rod. It is longer than the building in which it has to be, installed in the walls of the building during its construction. It has, sharp pointed spikes on the upper end which are fixed at the, highest point of the building. The lower end is connected to a large, metal (copper/aluminium) plate which is buried under the ground., , 8., , It prevents a person from getting electric shocks due to any, leakage of electric current., , 1. When a body comes in contact with the earth, either directly or, indirectly, then the charges are discharged to the earth. If you take, metal wire and connect one end with the strips of an electroscope, and touch the other end with your hand the metal strip comes back, to its original position. This happens as the metal strip loses, charges to the earth through your body. The process of transferring, of charge from a charged object to the earth is known as earthing., Devices for earthing are provided in buildings too., 2., , A physical quantity which is responsible for electrostatic force of, attraction or repulsion between matter is called electric charge.

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GURUKUL CENTRAL ACADMY, Refer Activity 4 “Types of Charges”., , 3., , 4., , 5., , 6., , Electroscope is a device used for the detection and measurement of, electric charge. When a charged object comes in contact with the, metal disc, it transfers its charges to it. The metal rod transfers, these charges to the strips and they repel. We can conclude the, presence of charges. The wider is the repulsion, the bigger is the, magnitude of charge., , Refer page 164., • Take shelter under a strong desk or a strong table till the shaking, stops., • Protect yourself from falling objects. Cover your head with a, pillow., • Avoid taking cover near windows, large mirrors, hanging objects,, heavy furniture, heavy appliances or fireplaces., • Move to an open area where falling objects are unlikely to strike., • Move away from buildings, power lines, signboards and trees., Lightning is a bright flash of electrical discharge produced, alongwith a thunderstorm., Lightning is caused due to electrical discharge. Due to friction with, wind and rain, a positive charge area is built on the ground below, the cloud. The ground electrical charges concentrate around, anything that sticks up such as a mountain, people or tree. The, accumulation of positive charges on the ground causes electrons, collected at the bottom of the clouds to jump. Once the electrons, start, moving, the air around it gets heated and glows. This causes a, lightning to strike.

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GURUKUL CENTRAL ACADMY, , 7., , An electrical neutral object can be charged through three different, processes—by friction, by conduction or by induction., Charging by friction: Rubbing of two objects against each other, produces friction. This friction between them leads to the transfer of, one type of charge from an object to the other. For example, when a, glass rod is rubbed with a silk cloth, negative charges are, transferred from the glass rod to the silk cloth. The glass rod, becomes positively charged, while the silk cloth becomes, negatively charged.