SCIENCE AND TECHNOLOGY—2004 (Set I— Compartment Delhi)


Q. 1. What wilt be the focal length of a lens whose power is given as + 2.0 D? 1

Q. 2. An alternating electric current has a frequency of 50 Hz. How many times does it change its direction in one second’? 1

Q. 3. Name an ore of zinc other than zinc oxide. By what process can this ore be converted to zinc oxide? 1

Q. 4. Write the name and the chemical formula of the organic acid present in vinegar. 1

Q. 5. Select metalloids from amongst the following elements. 1
(0 Bismuth (ii) Copper (iii) Zinc (iv) Arsenic (v) Iron

Q. 6. An electric bulb draws a current of 0.2 A when the voltage is 220 volts. Calculate the amount of electric charge flowing through it in one hour. 2

Q. 7. The use of dry wood as domestic fuel is not considered as good. State two reasons for it. 2

Q. 8. Explain the term “shooting starts”. How do they acquire brightness? What are they called if they reach the surface of the earth? 2

Q. 9. What are silica and cryolite chemically? State one use for each of them. 2

Q.1O. Give one example each for the formation of (i) addition polymers, and (ii) condensation polymers. 2

Q. 11. (a) State one special use of either pyrex glass or optical glass fibres. What is this based on?
(b) What is safety glass? 2, 1

Q. 12. (a) Which will be more acidic and why?
(i) A solution with pH value of 6.0, or (ii) A solution with pH value of 5.0.

(b) Calculate pH values for 1.0 M HCI solution and 1.0 M KCI solution assuming that the solutes are fully ionised. 1, 2

Q. 13. An object 3 cm high is placed at a distance of 20 cm in front of a convex lens of focal length 12 cm. Find the position, nature and size of the image formed.3
An object 3 cm high is placed at a distance of 9 cm in front of a concave mirror of focal length 18 cm. Find the position, nature and size of the image formed.

Q. 14. The flow of a current in a circular loop of wire creates a magnetic field at its centre. How may existence of this field be detected? State the rule which helps to predict the direction of this magnetic field. 3
How doas the strength of the magnetic field at the centre of a circular coil of wire depend on:
a) the radius of the coil
b) the number of turns of wire in the coil
c) the strength of current flowing in the coil

Q. 15. a) Explain what corrosion of iron means.
b) Why is it that aluminium which is more reactive than iron does not corrode like iron?
c) How is corrosion of iron prevented by coating i with a layer of oil? 3

Q. 16. Write balanced chemical equations for the reactions taking place when:
a) Concentrated sulphuric acid is added to cane-sugar (C12H22O11).
b) Dry blue crystals of copper sulphate are dropped into concentrated sulphuric acid.
c) Steam is passed over red hot iron. 3

Q, 17. Mention any two points of difference between terrestrial planets and Jovian planets. Choose Jovian planets from
a) Jupiter b) Mercury c) Saturn d) Uranus e) Venus

Q. 18. a) How is the fission of 235U brought about?
b) A nucleus has a mass number m and atomic number n. How will these numbers change in the following emissions per atom?5
(i) One alpha particle
(ii) A positron
(iii) A y-ray
(iv) An electron followed by a positron


Describe the construction of a box type solar cooker or show it with the help of a diagram. How is the rise in temperature obtained in this set-up? Mention two advantages and two limitations of solar cookers. 5

Q. 19. a) Express Ohm’s law both by mathematical formula and by a graph line.
b) State S.I. units of (i) resistance and (ii) resistivity.
c) What will be the equivalent resistance R of two resistors R1 and R2 (i) connected in series and (ii) connected in parallel? 2, 1, 2

Q. 20. State briefly the main steps involved in the extraction of iron metal starting with the raw ore. Write the chemical equations for the reactions involved at the various stages. Name the chief impurity present in the metal obtained. 4, 1

a) What is the fermentation process?
b) What role is played by yeast in the conversion of cane-sugar (C12H22O11) to ethanol?
c) How may the following be obtained from pure ethanol? Express chemical reactions by the corresponding chemical equations. 1,1,3
(i) Sodium ethoxide b) Ethy1 ethanoate c) Ethanal


Q. 21. What type of structure has been proposed for the DNA molecule? 1

Q. 22. Mention any two characteristics of homologous chromosomes. 1

Q. 23. Name the structural and functional units of human nervous system. 1

Q. 24. Why is it essential to match the blood groups of the ‘donor’ and the ‘receiver’ persons before arranging transfusion of blood? A person tests as ‘universal donor’. Which group of blood will be acceptable to him for receiving blood transfusion? 2

Q. 25. What is ‘eutrophication’? How does it influence aquatic life? 2
Mention any four practices that can help in conservation and protection of our environment.

Q. 26. State three points of difference between aerobic and anaerobic respiration. 3

Q. 27. Draw a diagram of a flower to show its male and female reproductive parts. Label on it:
a) The ovary b) The anther c) The filament d) The stigma 3

Q. 28. Write the cause of each of the following:
a) Acid rain
b) Depletion of ozone layer in the atmosphere
c) Green house effect in air 3

Q. 29. State the role of excretion in living beings. Describe how excretion takes place in amoeba. 3

Q. 30. Name the main organs of human digestive system in the order in which they are involved in digesting food. In what steps and how does digestion of, and proteins take place in our bodies? 5