SCIENCE AND TECHNOLOGY—2004 (Set II— Compartment Outside Delhi)

Except for the following questions, all the remaining questions have been asked in Set I.

Q. 3. What is the power of a convex lens of focal length 40 cm? 1

Q. 4. Write the name and chemical molecular formula of the compound used for preserving biological specimens. 1

Q. 5. How many times will the direction of a current change in one second if its frequency is 50 Hz? 1

Q. 6. Differentiate between a polymer and a monomer. Name the monomer of natural rubber. 2

Q. 8. Calculate the amount of charge that would flow in 2 hours through the element of an electric bulb drawing a current of 0.25 A. 2

Q. 9. Give two reasons why burning of firewood in traditional chulhas is considered disadvantageous. 2

Q. 12. What is meant by the term ‘pH of a solution’? The pH of rain water collected from two cities A and B was found to be 6 and 5 respectively. The water of which city is more acidic? Find the ratio of hydrogen ion concentration in the two samples of rain water. 3

Q. 14. Draw the pattern of lines of force due to a magnetic field through and around a current carrying circular ioop of wire. How would the strength of the magnetic field produced at the centre of the circular loop be affected if
a) the strength of the current passing through this loop is doubled?
b) the radius of this loop is reduced to one-half of the original radius? 3
With the help of a labelled diagram, explain the construction and the principle of working of a dry cell.

Q. 15. Find the position, nature and size of the image formed by a convex lens of focal length 18 cm of an object 3 cm high placed at a distance 27 cm from it. 3
Find the position, nature and size of the image of an object 4 cm high placed at a distance 10 cm from a concave mirror of focal length 20 cm.

Q. 18. State Ohm’s law. Express it mathematically. Define SI unit of resistance. Derive an expression for the equivalent resistance of three resistors R1 R2 and R3 connected in parallel. 5

Q. 23. Name the scientist who established the laws of inheritance. 1

Q. 28. Differentiate between ‘excretion’ and ‘osmoregulation’. Describe how excretion takes place in amoeba. 3