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Paper: CBSE Sample paper (Gold series) - XII - Physics - 12

Total marks of the paper: 70

Total time of the paper: 3 Hrs

Test instructions:General Instructions:(a) All questions are compulsory.(b) There are 30 questions in total. Questions 1 to 8 carry one mark each, questions 9 to 18 carry two marks each,questions 19 to 27 carry three marks each and questions 28 to 30 carry five marks each.(c) There is no overall choice. However, an internal choice has been provided in the one question of two marks; onequestion of three marks and all three questions of five marks each. You have to attempt only one of the choices insuch questions.(d) Use of calculators is not permitted.

Questions:

1] Is the force acting between two point electric charges q1 and q2 kept at somedistance apart in air attraction or repulsive when (i) q1q2>0 (ii) q1q2 W2) respectively.The kinetic energy of the emitted electron is same in boththe cases. Which one of the two radiation will be of higher frequency ?

[Marks:1]

7] How the magnetic moment of an electron will change if we double the frequency of its revolution? [Marks:1]

8] What will be the values of input A and B for the Boolean expression

?

[Marks:1]

9] Define di-electric constant of a medium. Briefly explain why the capacitance ofa parallel plate capacitor increases on introducing a di-electric mediumbetween the plates ?

[Marks:2]

10]

The distance of the field point on the equatorial plane of a small electric dipole,is halved. By what factor will the electric field, due to the dipole, change ?

[Marks:2]
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11]

A cylindrical metallic wire is stretched to increase its length by 5%.Calculatethe percentage change in its resistance.

[Marks:2]

12]

In an ammeter (consisting of a galvanometer and a shunt) 0.5% of the maincurrent passes through the galvanometer. Resistance of the galvanometer coilis G. Calculate the resistance of the shunt in terms of galvanometer resistanceG.

ORDefine intensity of magnetization of a magnetic material. How does it varywith temperature for a paramagnetic materials ?

[Marks:2]

13]

Name the phenomenon associated with the production of back emf in a coildue to change of electric current through the coil itself. Name and define the SI unit used for measuring this characteristic of the coil .

[Marks:2]

14]

a resistor of 30 and a capacitor of 0.25F are connected in series to a 100Vsource (=10,000 radian per second). Find the current in the circuit and the

rms voltage across the resistor and the capacitor. Is the algebraic sum of thesevoltages more than the source voltage? If yes, resolve the paradox.

[Marks:2]

15]

Identify the part of the electromagnet spectrum which isi. Suitable for radar system used in aircraft navigation.ii. Adjacent to the low frequency of the electromagnetic spectrum

iii. Produced in nuclear reactions.iv. Produced by bombarding a metal target by high speed electons.

[Marks:2]

16]

Calculate the focal length of the combination o f a convex lens of focal length30 cm in contact with a concave lens of focal length 20 cm. Is the system aconverging or a diverging lens ?

[Marks:2]

17]

Draw the curve showing variation of binding energy/nucleon with mass numberof different nuclei. Briefly state how nuclear fusion and nuclear fission can beexplained on the basis of this graph.

[Marks:2]

18]

With the help of diagrams, differentiate between (i) Pulse amplitude modulation(PAM) and (ii) Pulse position modulation (PPM).

[Marks:2]

19]

Two capacitors, of capacitance, 3F and 6F, are charged to potentials of 2Vand 5V respectively. These two charged capacitors are connected in parallel.Find the charge across each of the two capacitors now.

[Marks:3]

20

]State the principle of an ac generator. Write an expression for the maximumemf produced in it ?

[Marks:3]


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21]

[Marks:3]

22]

An incident beam of light of intensity I is made to fall on a Polaroid A. AnotherPolaroid B is so oriented with respect to A that there is no light emergeing out

of B. A third Polaroid C is now introduced midway between A and B. What isthe intensity of light now between(i) A and C?(ii) C and B?Give reasons for your answer.

[Marks:3]

23]

If the frequency of light falling on a metal is doubled, what will be the effect onphotocurrent and the maximum kinetic energy of emitted photoelectrons?Explain.

[Marks:3]

24]

If the nucleous of a nucleus are separated for apart from each other, the sum

of masses of all these nucleons is larger than the mass of the nucleus. Wheredoes this mass difference come from ? Calculate the energy released if238U nucleus emits an paricle[Given :

Atomic mass of238U= 238.0580 uAtomic mass of234Th = 234.04363 uAtomic mass of -particle = 4.00260 u

1u = 931 MeV]

[Marks:3]

25]

With the help of a diagram, show the biasing of a Light Emitting Diode. Statethe factor, which controls (i) wavelength of light and (ii) intensity of light,

emitted by a LED. Write any two advantage of Light Emitting Diode overconventional incandescent lamps.

[Marks:3]

26]

Name the gate obtained from the combination of gates shown in the figure.Draw its logic symbol. Write the truth table of the combination.

[Marks:3]


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27] Which mode of propagation is used by short wave broadcast services havingfrequencies range from a few MHz upto 3 MHz? Explain diagrammatically how

long distance communication can be achieved by this mode. Why is there anupper limit to frequency of waves used in this mode?

[Marks:3]

28]

[Marks:5]

29]

[Marks:5]

30]

ample PapersBag these Sample Papers for math and science & kick start your smart preparation for exams! Download 'n' solvepapers at your own convenience. Get detailed solutions, too. Also, get CCE compliant Summative Sample Papers,FREE!Back to listing page

Paper: CBSE Sample paper (Gold series) - XII - Physics - 12

Total marks of the paper: 70
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Total time of the paper: 3 Hrs

Test instructions:General Instructions:(a) All questions are compulsory.(b) There are 30 questions in total. Questions 1 to 8 carry one mark each, questions 9 to 18 carry two marks each,questions 19 to 27 carry three marks each and questions 28 to 30 carry five marks each.(c) There is no overall choice. However, an internal choice has been provided in the one question of two marks; one

question of three marks and all three questions of five marks each. You have to attempt only one of the choices insuch questions.(d) Use of calculators is not permitted.

Solutions:

1] When q1q2 > 0, force is repulsive, (ii) when q1q2 w2


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hence >

7] With doubling the frequency of revolution, the magnetic moment of electron alsodoubles.

8]

9] Dielectric constant : The dielectric constant of a medium is the ratio of theelectrostatic force of interaction between two given point charges held certaindistance apart in vacuum/air to the force of interaction between the same two

charges held the same distance apart in the material medium. Now, the capacity of parallel plate capacitor filled with air is given by

10]


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11]

12

]


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OR

The intensity of magnetization is the magnetic moment developed per unit volume ofa material when placed in a magnetising field. For a paramagnetic material, it isinversely proportion to the temperature.

13]

Back emf in a coil during change of electric current through coil is due to self-induction.S.I. unit of self-induction is Henry. Self inductance of a coil is said to be one

Henry if rate of change of current of 1 ampere per second induces an emf of 1 volt init.

14]

15]

(i) Microwaves(ii) Radiowaves(iii) Gamma rays(iv) X-rays


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16]

The system behaves as a diverging lens.

17]

Binding energy per nucleon vs Mass Number

Explanation of Nuclear Fission:When we move from the heavy nuclei region to the middle region of the plot, we find that there will bea gain in the overall binding energy and hence release of energy. This indicates that energy can bereleased when a heavy nucleus breaks into two roughly equal fragments. This process is calledNucler Fission.

Explanation of Nuclear Fusion:When we move from lighter nuclei to heavier nuclei, we again find that there will be again in the overall binding energy and hence release of energy. This indicates thatenergy can be released when two or more lighter nuclei fuse together to form aheavy nucleus. This process is called Nuclear Fusion.

18]

Pulse amplitude modulation : It is the process of modulation in which amplitude of

the pulses varies in accordance with the instantaneous value of the modulatingsignal.Pulse position modulation : It is a form of modulation in which timing or position ofthe pulse varies around a fixed mean value in accordance with the instantaneousvalue of the modulating signal.


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19]

Total charge = ( 3 2 + 6 5) C = 36 CLet V be the common potential across the two capacitors when they are connectedin parallel.Total capacitance of the parallel combination = (3 + 6) F = 9 F

20]

The working of A.C generator is based on phenomenon of electromagneticinduction. When a closed coil is rotated rapidly in a uniform magnetic field, themagnetic flux linked with the coil changes continuously which results in setting aninduced emf in the coil. This induced emf causes a current to flow in the coil.

Induced emf, E = NBA sin t

Emax = NBA (when sin t = 1)N = number of turns of coil

= angular speed of rotationB = strength of magnetic field

A = area of coil


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21]

22] According to Malus,

As no light passes through B, the angle between A and B is 90. Now C is sointroduced that axis of C bisects the angle between axes of A and B i.e., at 45 w.r.t

A. Hence angle between axes of C and B will be 90 - 45 = 45Given Io = 0


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23]

The photocurrent does not depend on the frequency of incident radiation, hence the

photocurrent remains unchanged. The maximum kinetic energy increases withincrease of frequency, given by

24]

When nucleons of nucleus are separated for apart from each other then the sum ofthe nucleons is greater than the mass of nucleus.This is direct mass defeat ofnucleus. Some mass has been converted into energy which holds the nucleoustogether.Given :Atomic mass of238U = 238.0580 u

Atomic mass of234Th = 234.04363 uAtomic mass of alpha-particle = 4.00260 u

1u = 931 MeVMass defect = 238.0580-(234.04363 + 4.00260)

= 238.05080 238.04623 = 0.00457 u

Emitted energy will be = 0.00457 931 = 4.25 MeV25]

Biasing of light emitting diode (LED) is shown in fig.


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Factors controlling wavelength and intensity:(i) Wavelength of light emitted depends on the nature of semiconductor. (ii) Intensity of light emitted depends on the forward current.

Advatage of light emitting diode over incandescent lamp: 1. LED operates at low values and consumes low power. 2. The light emitted by LED is nearly monochromatic.

26] NOR gate is obtained by the combination of gates shown :

Logical symbol of NOR gate

Input Output

A BY =

0

0

1

1

0

1

0

1

1

0

0

0

27]

The mode of propagation used by short wave broadcast services having frquencyrange from a few MHz upto 30 MHz is skywave propagation. The diagram is shown in fig.


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There is an upper limit of frequency because for frequency higher than 30 MHz, theradiowaves penetrate through the ionosphere and escape.


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28]


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29]


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