12th physics question paper 2012 – bihar board

Section – I (Objective Type)

1. 1 stat-coulomb =…………. Coulomb.

(a) 3 x 109 (b) 3 x 10-9

(c) (d)

2. A biconvex lens (µ = 1.5) has equal curvature each of 20cm. The power of the lens is

(a) 5 D (b) 10 D

(c) 2.5 D (d) 20 D

3. The equivalent capacity between points A and B is

(a) 4µF (b)

(c) 3µF (d)

4. The number of neutrons in an atom of 90Th230 is

(a) 90 (b) 140

(c) 230 (d) 320

5. The permeability (µ) of a ferromagnetic substance is

(a) µ > 1 (b) µ = 1

(c) µ < 1 (d) µ = 0

6. The peak voltage of an A.C. is 440 volts. Its virtual voltage is

(a) 220 V (b) 440 V

(c) (d)

7. The magnifying power of a magnifying glass of power 12 diopter is

(a) 4 (b) 1200

(c) 3 (d) 25

8. A current of 10 ampere flows in a wire for 10 sec. If potential difference across the wire is 15volt, the work done will be

(a) 150 J (b) 75 J

(c) 1500 J (d) 750 J

9. The logic gate shown in figure is

(a) OR (b) NOR

(c) NAND (d) AND

10. A monochromatic light of wavelength 6000 Å in vacuum enters a medium of refractive index 1.5. The wavelength of it in this medium is

(a) 4000 Å (b) 4500 Å

(c) 6000 Å (d) 9000 Å

In the following question Nos. 11 to 15 there are two statements. You have to go through these statements and choose the correct answer from the choices given below:

1. Both the statements are true and statement-II is the correct explanation of Statement-I
2. Both the statements are true, but Statement-II is not the correct explanation of Statement-I
3. Statement-I is true, but Statement-II is false
4. Statement-I s false, but Statement-II is true.

11. Statement-I: Balmer series lies in infrared region.

Statement-II: Lyman series lies in ultraviolet region.

12. Statement-I: If a body is negatively charged its mass slightly increases.

Statement-II: To charge a body transfer of electron is done.

13. Statement-I: Electromagnetic waves are transverse in nature.

Statement-II: Electromagnetic waves can be polarised.

14. Statement-I: All nuclei are not of same size.

Statement-II: The size of nucleus depends on atomic mass.

15. Statement-I: Magnetic flux is a vector quantity.

Statement-II: The value of magnetic flux may be positive, negative or zero.

In Question Nos. 16 to 18, there may be more than one correct answer among the four alternatives. You have to choose all the correct options and mark in the answer sheet.

16. When light travels from one medium to another which of the following factors charges?

(a) wavelength (b) frequency

(c) velocity (d) amplitude

17. Which among the following rays is not deflected by electric field?

(a) X-ray (b) ˠ-rays

(c) α-ray (d) Cathode ray

18. Among the following whose mass is not equal to the mass of an electron?

(a) Proton (b) Hydrogen

(c) Positron (d) Neutron

In the following Question Nos. 19 to 22, there are two columns. Column-I contains 4 questions. Our have to match the correct options of these questions (A), (B), (C) and (D) from Column-II.

Column-I Column-II

19. Brewster’s law (A) Interference
20. Liquid lens (B) Defect of image
21. Chromatic Aberration (C) Polarisation
22. Young’s double slit experiment (D) Human eye

V. For the following Question Nos. 23 to 25 a paragraph is given. You have to first go through that given paragraph and then answer the following three questions by indicating correct option. These questions carry tow marks each.

Paragraph

If two waves having amplitudes a and b superimposes on each other and resultant amplitude is A= = phase constant.

Intensity () is directly proportional to square of amplitude

∞A2 or, ∞ (a2+b2+2ab cos ɸ).

In constructive interference max. = (a+b)2.

In destructive interference  min= (a-b)2.

Light waves from two coherent sources producing interference have intensity ratio 81:1 using these information choose correct option form the following:

23. The ratio of maxima and minima in the interference pattern is

(a) 9:1 (b) 81:1

(c) 25:16 (d) 16:25

24. The ratio of amplitude of light waves from two sources is

(a) 9:1 (b) 81:1

(c) 1:9 (d) 1:81

25. For maximum intensity the value of cos ɸ is

(a) -1 (b) +1

(c) ∞ (d) 0

Section – II (Non- Objective Type)

Short Answer Type Questions

1. Define critical angle and write its conditions.
2. Find the equivalent capacity between A and B.
   
3. Write two differences between electromagnet and permanent magnet.
4. What is doping?
5. The half-life of radium is 1622 years. How long will it take for 7/8th of a given amount of radium of decay?
6. Why is core of transformer laminated?
7. What is Polaroid? Write its uses.
8. What is the value of i in the given circuit?

9. Write two basic properties of electric charge.
10. State two factors by which the range of transmission of TV signal can be increased.
11. Give the symbol and truth table for AND gate.

Long Answer Type Questions

12. Define electric flux.  State and prove Gauss theorem.

Or

A metallic sphere of radius 9cm has been given a charge of 4 x 10-6C. Calculate energy of charged conductor.

13. Establish the formula

Or

Define Interference. Derive expression for fringe width in Young’s double slit experiment.

14. Explain with the help of a diagram the principle, construction and working of a cyclotron.12th physics question paper 2013 – Bihar board

Or

Explain Biot-Savart law. Derive expression for the magnetic field at the center of a current carrying circular loop.

15. Define Radioactivity. Write the nature, properties and difference among α, β and ˠ rays.

Or

What is Zener diode? Explain its use as a voltage regulator.