Wrong match about the uses of polymers is ,
(A)Polystyrene.........Wrapping material, insulator
(B)PVC .........Rain coats, Hand bags
(c) Bakelite ......... Substitute to wool
(D) Glyptal ..........Paints and Lacquers

Which of the following is the incorrect use? (A) Glyptal - Lacquers (B) PVC - Rain coats (C) Nylon 6 6- Bristles for brushes (D) Bakelite - squeeze bottles

Which of the following is a chain growth polymer? (A) Orlon (B) Dacron (c) Glyptal (D) Bakelite

In a village, farmers started cultivating crops all around a lake which was always filled with water. They added lot of materials W to the soil in their fields to increase the yield of crops. Soon they found that the whole surface of water in the lake was covered with a green layer made up of tiny organisms X. After some time, the fish present in the lake started dying in large numbers they could not get sufficient Y due to a process Z which had occurred in lake water and drained out all the Y present in the water of lake. (a) What do you think materials W are ? (b) Name (i) X, and (ii) Y. (c ) What is the process Z known as ? (d) What happens during the process Z which uses up all the Y present in lake water ? (e) What does this example tell us about the use of materials like W ?

Answer the following question: (a) Explain qualitatively on the basis of domain picture, the irreversibility in the magnetisation curve of a ferromagnet. (b) The hysteresis loop of a soft iron piece has a much smaller area than that of a carbon steel piece. If the material is to go through repeated cycles of magnetisation, which piece will dissipate greater heat energy? (c) A system displaying a hysteresis loop such as ferromagnet is a device for strong memory? Explain the meaning of this statement. (d) What kind of ferromagnet material is used for coating magnetic tapes in a cassette player, or for building memory stores in a modern computer? (e) A certain region of space is to be shielded from magnetic fields. Suggest a method.