Sample paper 2 kho tài liệu bách khoa

iii Question number 1 to 5 are very short answer questions, carrying 1 mark each.. iv Question number 6 to 12 are short answer questions, carrying 2 marks each.. v Question number 13 to

Sample Question Paper – II

General Instructions

(i) All questions are compulsory

(ii) There is no overall choice However, an internal choice has been provided in one question

of two marks, one question of three marks and one question of five marks You have toattempt only one of the choices in such questions

(iii) Question number 1 to 5 are very short answer questions, carrying 1 mark each

(iv) Question number 6 to 12 are short answer questions, carrying 2 marks each

(v) Question number 13 to 24 are also short answer questions, carrying 3 marks each

(vi) Question number 25 to 27 are long answer questions, carrying 5 marks each

(vii) Use of calculators is NOT permitted However, you may use Log Tables, if necessary

(viii) You may use the following physical constants wherever necessary:

c = 3 × 108 ms–1

h = 6.6 × 10–34 Js

e = 1.6 × 10–19 C

µ0 = 4π × 10–7 T mA–1

1. Write the SI unit of (i) potential gradient (ii) electric dipole moment 1

4. A thin prism of refracting angle 2° deviates an incident ray through an angle of 1° Find the

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5. A radioactive nucleus decays by emiting a β-particle How will the proton-neutron ratio ofthe daughter nucleus change as compared to the parent nucleus? 1

6. Name one ohmic material and one non-ohmic device Draw V-I graph for each. 2

7. Define angle of dip at a place How does its value change as one goes from magnetic pole to the

10. The truth table of a logic gate is given below

INPUTS OUTPUT

A B Y

0 0 1

1 0 1

0 1 1

1 1 0

11. A student is asked to calculate the ratio of electric flux through the surfaces of spheres S1 and S2 with charges placed inside, as shown in the figure He gets the answer as 4 : 1 Check the correctness of the answer by actually calculating the electric flux ratio through the two surfaces

5cm

10cm

mC

3 C m

S 2

12. In a part of the circuit shown in the figure, the rate of heat dissipation in 4Ω resistor is 100 J/s Calculate the heat dissipated in the 3Ω resistor in 10 seconds 2

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2 4

13. Name the constituent radiation of electromagnetic spectrum which

(i) is similar to the radiations emitted during decay of radioactive nuclei.

(ii) has its wavelength range between 390 nm and 770 nm.

(iii)is used in satellite communication.

(iv) is absorbed from sunlight by the ozone layer

(v) is used for studying crystal structures.

14. Define the terms ‘solar constant’ and ‘solar luminosity’ Write the relation between the two 3

15. What do the acronyms LASER and LED stand for? Name the factor which determines (i) quency (ii) intensity of light emitted by LED State the basic difference between the light

16. A proton and an alpha particle enter at right angles in to a uniform magnetic field of intensity B.

Calculate the ratio of the radii of their paths, when they enter the field with the

(i) same momentum,

17. Write two differences between interference and diffraction

Two plane monochromatic waves propagating in the same direction with amplitudes A and 2A

and differing in phase by π/3 superpose Calculate the amplitude of the resultant wave 3

18. A ray of light goes from medium 1 to medium 2 Velocity of light in the two media are c1 and c2

respectively For an angle of incidence θ in medium 1, the corresponding angle of refraction inmedium 2 is θ/2

(i) Which of the two media is optically denser and why?

19. Calculate the de Broglie wavelength associated with an electron of energy 200 eV What will bethe change in this wavelength if the accelerating protential is increased to four times its earlier

20. Prove mathematically that the fraction N/N0, of a radioactive element left over after a time t equals 1/x where x = 2 t/T and T denotes half life period of the radioactive element. 3

21. Mention any two special characteristics of light sources used in optical communication

Ex-plain the meaning of the terms (i) sensitivity (ii) responsivity of the detector used in an optical

22. Two metallic wires of the same material and same length but different cross sectional areas are

joined together (i) in series (ii) in parallel, to source of emf In which of the two wires will the

drift velocity of electron be more in each of the two cases and why? 3

OR

22. Six equal resistors, each of value R, are joined together as shown in the given figure Calculate

the equivalent resistance across AB

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A

B C

If a supply of emf E is connected across AB, compute the currents through the arms DF and that

through the battery

23. A rectangular coil P is moved from a point A to another point B with uniform velocity v through

a region of a uniform magnetic field acting normally inwards as shown in the figure Showgraphically

(i) the variation of magnetic flux associated with the coil with time.

(ii) variation of induced emf across points X and Y of the coil with time.

X Y

v

P

X X X

24. Two convex lenses A and B of an astronomical telescope having focal lengths 5 cm and 20 cmrespectively, are arranged as shown in the figure.

15cm

(i) Which one of the two lenses you will select to use as the objective lens and why?

(ii) What should be the change in the distance between the lenses to have the telescope in its

normal adjustment position?

(iii)Calculate the magnifying power of the telescope in the normal adjustment position.

25. Explain the formation of the depletion layer and the barrier potential in a p-n junctiondiode Also explain with the help of a circuit diagram, its use as a full wave rectifier Draw the

26. Two circular metal plates, each of radius 10 cm, are kept parallel to each other at a distance of

1 mm What kind of capacitor do they make? Mention one application of this capacitor

If the radius of each of the plates is increased by a factor of √2 and their distance of separationdecreased to half of its initial value, calculate the ratio of the capacitance in the two cases.Suggest any one possible method by which the capacitance in the second case be increased by

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27. Distinguish between the terms resistance and impedance of an a.c circuit A capacitor C and a resistor R are connected in series in an a.c circuit Deduce, by drawing phasor diagram, a

mathematical expression for the impedance of this circuit How will this impedance be affectedwhen the frequency of the applied signal is decreased and why? 2+2+1=5

OR

An inductor L, a capacitor C and a resistor R are connected in series in an a.c circuit Deduce,

with the help of suitable phasor diagrams, a mathematical expression for impedance of thiscircuit

What is meant by resonance of this circuit? Prove that this circuit exhibits resonance at a

fre-quency give by 1

ANSWERS

1. (i) Volt/m or N/C

Mercury cell, Lithium cell, Silver oxide cell, Alkaline cell

3. Statement of function of a modem:

modulation demodulation

modem converts digital to analog signals (modulation)

and vice-versa (demodulation)

5. There will be increase in the proton-neutron ratio 1

6. Metallic conducting wire/resistance wire ½

V I

p-n junction/copper voltameter or any other ½I

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8.

2A A

10V

1A 1A

x 2A

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220 220

100

×

= = 484 Ω ½

P.D across the bulb = IR

1 484

4

= × = 121 V ½

14. Solar constant (S) is defined as the amount of radiant energy received per second by a unit area

of a perfectly black body surface held at right angle to the direction of sun rays at the meandistance of the earth from the sun 1

Solar luminosity (Ls) is defined as amount of total energy emitted per second by the sun in all

where r is the mean distance of the earth from the sun.

15. LASER — Light Amplification by Stimulated Emission of Radiation ½

(i) Frequency of light emitted by LED depends on gap in energy band of PN junction ½

(ii) Intensity of light emitted by LED is determined by its forward current at PN junction ½

LASER: Light emitted is coherent and monochromatic ½LED: Light emitted is noncoherent ½

(i) For same momentum

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2 cos

2sin

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21. Characteristics (any two)

(i) Size of the source should be small

(ii) Light source should produce monochromatic light

(iii) Should be capable to rapid switching

Sensitivity: It is the measure of the ability of a detector and determines how weak a signal can

be detected

Responsivity: The ability of the optical detector to respond quickly to the changing light pulsesthat are rapidly switching ON and OFF

Name of optical detectors (any two)

Silicon photo-diodes, Avlanche Photo Diodes (APD), photo-transistors, photo-resistors

∴ thinner wire will have greater vd

(ii) In parallel, V is same

R R R R

R E

D

R R

R

F R

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I I I ITotal resistance

R

23.

Explanation variation of magnetic flux with time, magnetic flux is proportional to the area

of coil associated with flux Area of the coil in the field increases linearly with time Thenremains constant when the coil is completely in the magnetic field After this flux de-creases linearly with time and goes to zero till it comes out of the magnetic field 1½

24. (i) Objective lens – B because it has larger focal length and larger aperture ½

(ii) The distance between the lenses has to the increased by 10 cm. 1

25. Explanation of depletion layer 1Explanation of barrier potential 1Circuit diagram of full wave rectifier 1½Description of how it is used as full wave rectifier 1

V

t t

26. (i) Parallel plate capacitor Applications:- ½

(a) to store electrostatic energy

(b) it can be used in an oscillatory circuit, when combined with an inductor ½

C

d

ε π

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C

(iii) (a) By introducing a dielectric having a dielectric constant n, between the plates (b) By decreasing the distance between the plates by a factor of n

(c) By increasing the area of plates n times (any one)

(d) By increasing the area of plates n times and simultaneously decreaing the distancebetween plates by a factor n 1

27. Distinction between resistance and impedance 2

Circuit diagram for series CR circuit Phasor diagram for series CR circuit Derivation of

Circuit diagram for series LCR circuit ½

Phasor diagram for series LCR circuit ½

Derivation of mathematical expression

1/ 2 2