CBSE CLASS 12 PHYSICS SAMPLE PAPER
General
Instructions:
1. All questions are compulsory.There are 26
questions in all.
2. This question paper has 5 sections.
3. Section A contains five
questions of one mark each,Section B contains five questions of two
marks each,Section C contains twelve questions of three marks each,Section D contains one value based question of four
marks and Section E contains three questions of five marks each.
4. There is no overall choice,however
internal choice has been provided in one
question of three marks and all questions of five marks.
Section - A
1. A 500 µc charge is
at the centre of a square of side 10 cm.Find the work done in moving a charge
of 10 µc between two diagonally opposite points on the square.
2. A converging lens of
refractive index 1.5 is kept in a liquid medium having same refractive index.what
would be the focal length of the lens in this medium?
3. The output of a two
input AND gate is fed to a NOT gate. Draw the logic circuit of this combination
of Gates and name it.
4. Show the variation
of photo current with collector plate potential for different intensity by same
frequency of incident radiation.
5. Give an example of a
material is for which temperature coefficient of resistivity is-
(i) Positive
(ii) Negative
Section - B
6. Distinguish between
EMF(E) and terminal voltage(V) of a cell having internal resistance
‘r’ .Draw a plot showing the variation of terminal voltage versus current drawn
from the cell. Using this plot, how does one determine the internal resistance
of the cell?
7.The value of ground
state energy of hydrogen atom is -13.6 electron volt.
(i) Find the
energy required to move an electron from the ground state to the first excited
state of the atom.
(ii) Determine the
kinetic energy in the first excited state of the atom.
8. A nucleus 10Ne23
undergoes beta decay and becomes 11Na23.
Calculate the maximum kinetic energy of electrons emitted assuming that beta
particle and Antineutrino carry negligible kinetic energy.
Mass of 10Ne23 =
22.99 4466 u
Mass of
11Na23 = 22.989 770 u
1 u = 931 .5 Mev/c2
9. A Ray of light
passing through an equilateral triangular glass prism from air undergoes
minimum deviation when angle of incidence is 3/4th of the angle of prism.
Calculate the speed of light in the prism.
10. The input waveforms
‘A’ and ‘B’ and the output waveform ‘Y’ of a gate are shown below. Name the
gate it represents, write its truth table and draw the logic symbol of this
gate.
11. The potential
difference across a resistor ’r’ carrying current ‘I’ is ‘Ir’ .
(i) Now if the potential
difference across ‘r’ is measured using a voltmeter of resistance ‘R’ , show
that the reading of voltmeter is less than the true value.
(ii) Find the percentage
error in measuring the potential difference by a voltmeter.
(iii) At what value of R, does
the voltmeter measures the true potential difference?
12. The magnetic field through
a single loop of wire 12 cm in radius and 8.5 ohm resistance, changes with time
as shown in figure. The magnetic field is perpendicular to the plane of the
loop. Plot induced current as a function of time.
13. Write three
characteristic features in Photoelectric effect which cannot be explained on
the basis of wave theory of light.
14. Right Maxwell's
modification of Ampere's circuital law. Show that in the process of charging a
capacitor, the current produced with in the plates of the capacitor is,
I = єo(dφe/dt)
15. Explain the need of
modulation.
16.(a) State Bohr’s
quantization condition for defining stationary orbits. How does de -Broglie
hypothesis explain the stationary orbits?
(b) Find relation between
three wavelength λ1, λ2 and λ3 from the energy
level diagram.
17.(i) Write a basic
nuclear process involved in the emission of β+ in a symbolic form,
by a radioactive nucleus.
(ii) in the
reactions given below-
6C11 → yBz
+ x + Ê‹
6C12 + 6C12
→ aNe20 + bHec
Find the values of x, y, z, a, b, and c.
18.(i) Explain with the
help of a diagram, the formation of depletion region and barrier potential in a
p-n Junction.
(ii) Draw the circuit
diagram of Full wave Rectifier and explain its working.
19. (i) State the advantages
of Reflecting type telescope over Refracting type.
(ii) Write the expression
for resolving power of a compound microscope. How can the resolving power of a
microscope be increased.
20. (i) Describe the working
of photodiode by drawing its circuit diagram.
(ii) Draw the
characteristics of a photodiode for different illumination intensities.
21. Deduce the
expression for the torque acting on a dipole placed in a uniform electric
field.
OR
Deduce the expression for potential energy of
the dipole. Find out the work done in rotating it from the position of unsstable
equilibrium to the stable equilibrium.
22.Two identical coils P
and Q each of radius R are lying in perpendicular planes such that they have a
common centre. Find the magnitude and direction of magnetic field at the common
centre of two coils, if they carry currents equal to I and √3I
respectively.
Section - D
23. Gautam went for a
vacation to the village where his grandmother lived his grandmother took him to
watch Nautanki one evening. They noticed a black box connected to the mic line
nearby. Goutam's grandmother did not know what that box was. When she ask this
question to Gautam he explained to her that it was an amplifier.
(i) Which values were
displayed by grandmother? Which values are displayed by Gautam.
(ii)What is the function
of an amplifier?
(iii) Which basic
electronic device is used in the amplifier?
Section - E
24. (i) State the essential
conditions for diffraction of light.
(ii) Explain diffraction
of light due to a narrow single slit and the formation of pattern of fringes on
the screen.
(iii) Find the relation
for width of Central Maxima in terms of wavelength λ , width of slit
a and separation between the slit and screen D.
(iv) If width of Slit is
made double, how does it affect the size and intensity of Central band.
OR
(i) Draw a labelled
diagram of astronomical telescope in normal adjustment.
(ii) Derive expression
for magnifying power of Astronomical Telescope when image is formed at least
distance of distinct vision.
25. A 2 µF capacitor, 100
ohm resistor and 8 H inductor are connected in series with an AC source.
(i) What should be the
frequency of the source such that the current drawn in the circuit is maximum? What
is this frequency called?
(ii) If the peak value of
EMF of source is 200 volt, find the maximum current.
(iii) Draw a graph showing
variation of amplitude of circuit current with changing frequency of applied
voltage in a series LRC circuit for two different values of resistance R1
and R2( R1> R2).
(iv) Define the term ‘sharpness
of resonance’. Under what condition, does a circuit become more selective.
OR
(i) With the help of a
neat labelled diagram, explain the principle and working of a moving coil
galvanometer.
(ii) What is the function
of uniform radial field and how is it produced?
(iii) Define current
sensitivity of a galvanometer. How is current sensitivity increased?
26. With the help of a
circuit diagram explain the working of CE transistor as an amplifier.
OR
(a) Show that in a
parallel plate capacitor, if the medium between the plates of a capacitor is
filled with an insulating substance of dielectric constant k, its capacitance
increases.
(b) Deduce the
expression for the energy stored in a capacitor of capacitance C with charge Q.
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