PHYSICS 2005 (Set I—Compartment Outside Delhi)
Q. 1. Write one condition under which an electric charge does not experience a force in a magnetic field. 1
Q. 2. Write S I unit of magnetic field. 1
Q. 3. When a lamp is connected to an alternating voltage supply, it lights with the same brightness as when connected to a 12V DC battery. What is the peak vlaue of alternating voltage source? 1
Q. 4. Why is the conductivity of n-type semiconductor greater than that of the p-type semiconductor even when both of these have same level of doping? 1
Q. 5. Name the process by which exact reproduction of a document at a distant place can be received. 1
Q. 6. Define the term 'temperature coefficient of resistivity'. Show graphically the variation of resistivity with temperature for nichrome. 2
Q. 7. Write the expression for frequency of an ideal LC circuit. In an actual circuit, why do the oscillations ultimately die away? 2
Q. 8. Monochromatic light is refracted from air into glass .of refractive index n, Find the ratio of wavelengths of the incident and refracted light. 2
Write two conditions necessary for total internal reflection to take place.
Q. 9. An electron and a proton have the same kinetic energy. Which of the two has a greater wavelength? Explain. 2
Q. 10. Define the term threshold frequency and work function in relation to Photoel- ectric effect. 2
Q. 11. Two signals A and B' shown in the figure are used as two inputs of an AND gate. Obtain its output wave form. Draw the logic symbol of AND gate. 2
Q. 12. With the help of diagrams distinguish between forward biasing and reverse biasing of a p-n diode. 2
Q. 13. A system has two charges q A = 2.5 x 10 -7 C and q B = - 2.5 x 10 -7 C located at points A (0, 0, - 15 cm) and B (0, 0, + 15 cm) respectively. Calculate the electric dipole moment of the system. What is its direction? 3
Q. 14. A battery of emf 10 V and internal resistance is connected to a resistor R.
Q. 15. With the help of circuit diagram explain in brief the use of a potentiometer for comparison of emf of two cells. 3
Q. 16. How will a dia-,para-and a ferro-magnetic material behave when kept in a non-uniform external magnetic field? Give one example of each of these materials. 3
Q. 17. With the help of a labelled diagram explain in brief the working of a cyclotron.3
Q. 18. Name the radiations of electromagnetic spectrum which are used in
Q. 19. Using Huygen's principle, explain the refraction of a plane wavefront at a plane surface. Hence prove Snell's law. 3
The figure given below shows an experimental set up for Young's double slit experiment to observe interference of light on the screen OP.
Here path difference SS 2 - SS 1 = . Obtain the condition for (i) constr- uctive, and (ii) destructive interference at any point P in terms of path difference, .
Q. 20. Draw a labelled diagram of experimental setup of Rutherford 's alpha particle scattering experiment. Write two important inferences drawn from this experiment. 3
Q. 21. The sequence of stepwise decays of a radioactive nucleus is
If the nucleon number and atomic number for D2 are 176 and 71 respectively, what are the corresponding values of D and D3 ? Justify your answer in each case. 3
Q. 22. Explain the term remote sensing in communication. Name the satellite used for this purpose. Mention its any two applications. 3
Q. 23. Explain the terms (i) pulse-amplitude modulation (PAM) and (ii) pulse-code modulation (PCM). Which modulation is preferred in transmitting signals and why? 3
Q. 24. Explain, with the help of a circuit diagram, the use of n-p-n transistor as an amplifier in common emitter configuration. 3
Q. 25. A dielectric slab of thickness 't' is kept in between the plates, each of area 'A', of a parallel plate capacitor separated by a distance 'd'. Derive an expression for the capacitance of this capacitor for t << d. 5
(a) Explain briefly how a capacitor stores energy on charging. Obtain an expression for the energy thus stored.
Q. 26. Draw a labelled diagram of a compound microscope when the image is formed at infinity. Deduce the expression for its magnifying power. How can the magnifying power be increased? 5
Draw a labelled diagram to show the image formation in an astronomical tele scope. Write an expression for its magnifying power.
Why should the objective lens of such a telescope have large diameter?
Q. 27. With the help of a neat and labelled diagram, explain the principle, construction and working of an a.c. generator. 5
Explain, with the help of a neat and labelled diagram, the principle, constructi- on and working of a transformer.
Physics 2005 Question Papers Class XII
CBSE 2005 Question Papers Class XII