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Basic Science, Lesson : 7, Attraction and Repulsion, Answer the following questions., , 1. Pictures of magnets are given below. Write their names and relation to, the picture., a., b., , Ans) Bar magnet, Ring magnet, Ring magnet., 2. What is meant by magnetic poles?, Ans) The parts of the magnets having greater force of attraction are called, magnetic poles., 3. Why a freely suspended magnet comes to rest in north ?, Ans) A freely suspended magnet comes to rest in north south direction because, the earth acts like a magnet. The north pole of the terrestrial magnet is near the, south pole of the Earth and the south pole of the terrestrial is near the north pole, of the Earth., 4. What is meant by natural magnets? What are their peculiarities?, Ans) Natural magnets are found in nature. They have very poor strength and, therefore they are used rarely., 5. Which alloy is used for making strong magnets?, Ans) Strong magnets are made using alnico which is an alloy of aluminium,, nickel, iron and cobalt., 6. Suggest a way in which a steel rod can be converted into a permanent, magnet by using the following materials., Bar magnet, Insulated copper wire, Cells., Ans) By rubbing with a bar magnet.

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7. Suggest ways to mark the pole of an unmarked bar magnet., Ans) If a long magnet is suspended at its middle using a thread so that it is, capable of free movement in the horizontal plane., it stands in the north south, direction. Even if it is turned a little to oneside it will finally come to rest in the, north south direction., 8. Of two identical substances one is an iron piece and the other is a, magnet. How do you distinguish between the two?, Ans) Suspended the two objects freely by means of a thread. Magnet sets itself, in the north- south direction but the other metal does not set in this direction., , 9., A, , B, , C, , Magnetic substance, , Magnetite, , Cobalt, , South pole, , Nickel, , High permeability, , Natural magnet, , iron, , Very poor strength, , Alnico, , North pole, , Attracts, , Ans), A, , B, , C, , Magnetic substance, , iron, , High permeability, , South pole, , North pole, , Attracts, , Natural magnet, , Magnetite, , Very poor strength, , Alnico, , Nickel, , Cobalt