2006 (Compartment Delhi)
General Instructions: 1. All questions are compulsory. 2. There is no overall choice. However, an internal choice has been pro vided in one question of two marks, one question of three marks and all three questions of five marks. You have to attempt only one of the choices in such questions. 3. Question numbers 1 to 5 are very short answer type questions, carrying one mark each. 4. Question numbers 6 to 12 are short answer type questions, carrying two marks each. 5. Question numbers 13 to 24 are also short answer type questions, carrying three marks each. 6. Question numbers 25 to 27 are long answer type questions, carrying five marks each. 7. Use of calculators is not permitted However, you may use log tables, f necessary. 8. You may use the following values of physical constants wherever necessary. Q. 1. Write two properties of a material used as a suspension wire in a moving coil galvanometer. 1 Q. 2. Name the experiment which establishes the wave nature of a particle. Q. 3. Write the S.I. unit for the activity of a radioactive nuclide. 1 1
Q. 4. The a.c. current gain of a transistor is 120. What is the change in the collector current in the transistor whose base current changes by Q. 5. Name the underlying principle of the working of an optical fibre. 1 1
Q. 6. Define ‘dielectric constant’ of a medium. Briefly explain why the capacitance of a parallel plate capacitor increases, oii introducing a dielectric medium between the plates. 2 Q. 7. Why does a paramagnetic substance display greater magnetisation for the same magnetising field when cooled? How does a diamagnetic substance respond to similar temperature changes? 2 Q. 8. Explain how electron mobility changes for a good conductor when (i) the temperature of the conductor is decreased at constant potential difference and (ii) applied potential difference is doubled at constant temperature. 2 Q. 9. A capacitor and a resistor are connected in series with an a.c....