CBSE Guess > Papers > Important Questions > Class XII > 2013 > Physics > Physics - by Mr. Raghu Sharma

CBSE CLASS XII

Physics

21. A diode is connected to 220 V (r.m.s.) a.c. in series with a capacitor, as shown in the figure. What is the voltage V across the capacitor ?

22. An electron, an alpha-particle and a proton have the same kinetic energy. Which one of these particles has the   largest d- Broglie wavelength.
23. Write an expression for resistivity of a metallic conductor showing its variation over a limited range of  temperature.
24. Magnetic field lines can be entirely confined with in the core of a toroid, but not with in a straight solenoid why?
25. How much average power dissipates, over a complete cycle of an A.C. source supply when connected to a capacitor?
26. A glass lens of refractive index 1.45 disappears when immerse in a liquid. What is the value of refractive index  of the liquid?
27. The radioactive isotope D decays according to the sequence
    D........DECAY.........D₁..........ἁ DECAY............D₂  If the mass number and atomic number of D₂ are 176 and 71 respectively, what is the
    1. mass number and
    2. atomic number of D

28. Two lines A and B in the plot given below show the variation of de Broglie wavelength, λ versus 1/√v, where V  is accelerating potential difference, for the two particles carrying the same charge. Which one of two represent a particle of smaller mass?
29. Two nuclei have mass number in the ratio 1: 2 what is the ratio of their nuclear densities?
30. An electron moving through a magnetic field does not experiences a force. Under what condition is this possible?
31. The instantaneous value of voltage from an a.c. Source is given by E=300 Sin 314t. What is the r.m.s. voltage of the source?
32. A bulb and a capacitor are connected in series to an a.c. source of variable frequency. How will the brightness of the bulb change on increasing the frequency of the a.c. source.
33. Name the part of electromagnetic spectrum that has largest penetrating power.
34. When light undergoes refraction. What happens to its frequency.
35. In the given diagram, is the diode D forward or reversed  biased?

36. Write the truth table for the gate shown below.

37. Two point charges 4µc and —2µc are separated by a distance of 1m in air. At what point on the line joining the two charges is the electric potential is zero.
38. Four resistors of resistance each of 10Ω is connected as given below.

Calculate the equivalent resistance between points X and Y
39. Explain how the width of depletion layer in a p-n junction diode changes when the junction is
    1. forward biased
    2. reverse biased.
40. How does the resistivity of
    1. a conductor and
    2. a semiconductor vary with temperature? Give reason for each case.

Submitted By : Mr. Raghu Sharma
Email: [email protected]