» Class XII Model Test Paper : CBSE Sample Question Papers

1. Galaxies are of many types. What type of galaxy is the milkyway?
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2. What is distance of nearest approach?
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3. Show that NC ^-1 and Vm^-1 represent the same physical quantity.
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4. Which gas acts as shield for ultra-violet radiations?
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5. What is the quantity whose unit is seimen metre?
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6. What are fast breeder reactors?
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7. What is meant by extrinstic semiconductor?
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8. Eye is most sensative to green light but danger signals are red. Why so?
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9. Earth is quite warm. What.effect keeps it warm 7 Explain in 2-3 lines.
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10. What are SI units of R/L and CR?
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11. Show that in the region of strong electric fields, equipotential surfaces are close together.
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12. A circuit having an inducting reactance of 25 Ω, a capacitor of capacitive reactance of 31 Ω and resistor of reistance 8 Ω are all placed in series. What is the total impedance of the circuit?
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13. A voltmeter measuring 0-2 V has a resistance of 100 ohm. How can it be converted into an ammetre of range 0-5 A.?
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14. What are nuclear reactions? Name the conservation laws which must be obeyed for a nuclear reactions to start.
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15. What is Joule’s law? Deduce an expression for the heat produced in a wire when a current / flows through a resistor JR.
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16. Why capacitor blocks D.C., whereas inductor allows it an easy path. What offers larger resistance to A.C?
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17. What is (110 100 111)₂ equal to?
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18. Why is the conductivity of an electrolyte very low as compared to a metal at room temperature?
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19. What are the laws of radioactive distintegratibn 7 how can the life of a rock be determined?
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20. Derive an expression for magnetic field at a point on the axis of a current loop.
How from this can we deduce magnetic field at the centre of the current carrying circular coil?
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21. A silver rod 1 m long and 1. 0 X 10^-4 m² area cross-section has one free electron per atom. Calculate (a) the number of free electrons in the rod, (b) the, drift velocity of the electrons if the current through the rod is 4A. Given the density of silver = 10.5 X 10³ kg m^-3 and mass number of silver = 108.
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22. Derive the expression for magnetic field acting at a point on the axis of a circular coil carrying current.
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23. Derive an expression for torque acting on a current carrying rectangular loop placed in the magnetic field.
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24. What is Q-factor of a series resonance circuit 7 what are uses of series resonant circuit?
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25. What are the properties of e.m. waves?
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26. A narrow monochromatic beam of light of intensity I is incident on a glass plate P as shown in figure. Another identical glass plate Q is held parallel and very close to P. Each glass plate reflects 25% of the light incident on it and-transmits the remaining. Find the ratio of min¬imum and maximum intensities in the inter¬ference pattern formed by the two beams obtained after one reflection at each plate.
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27. Derive the mirror formula for concave mirror forming virtual image.
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28. Compute the equivalent capacitance of the following combination be¬tween A and D if C₁ = C₂ = C₃
= C₄ = C₅ = 8µF. If a battery of 10V is connected between these points, what will be the charge on eacli capacitor?
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What is Gauss theorem? Derive an expression for electric field intensity at a point inside two parallel sheats of charge and hence capacitance of a parallel plate capacitor with a conducting slab.
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29. What is Lenz maker’s formula? Derive an expression for Lenz maker’s formula for a convex lens.
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30. What is meant by rectification? How can we use diodes to get full wave A.C. rectified? How can the output be smoothened?
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1. What is the absorption spectrum?
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2. What is Bohr magneton?
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3. Define relative permittivity. What substance has maximum relative permittivity?
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4. A resistor has white, grey, red and golden lines. What is its resistance?
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5. What is the force acting on a charge of 5C moving with a velocity of 20 ms^-1 in the direction opposite to the field of strength 4T?
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6. What is the role of back e.m.f. in d.c. motor?
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7. What type of material is used for making permanent magnets?
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8. What are radio-isotopes?
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9. What is terminal F.D. of a cell? How is it related to e.m.f. of a cell?
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10. A proton and an a-particle enters a uniform magnetic field perpendicularly with the same speed. How many times is the time period of the a-particie is than that of proton?
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11. What is self inductance? Define coefficient of self inductance. Give its SI unit.
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12. A lens of glass of refractive index 1 -50 is immersed in water of refractive index 1 - 33. Compare the focal length of lens in air to that in water.
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13. How will you define nuclear radius? Determine the density of a nucleus (approximately).
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14. What gate does the following Boolean relation represent A. B + A. B? Give its truth table.
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15. Light from a lamp falls on a wooden table but no photoelectrons emitted from it but when it falls on an alkali metals, they are emitted. Why so? What is work function and how is it related to frequency?
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16- What is mass defect?
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17- Distinguish between electric and magnetic field.
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18. You are having three resistors each of value R. How will you connect these to obtain a total resistance of 3 R/2? Show this by drawing suitable diagram.
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19. What is pure spectrum? How can it be produced in laboratory?
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20. Deduce the conditions of constructive and destructive interference.
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21. How can a transistor be used as an oscillator? What is meant by feedbeck?
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22. A circuit containing a pure resistor of 40 Ω is fed by a 200 V, 50 Hz A.C. mains. The current is reduced to half of its value when (i) a pure inductor, (ii) pure capacitor is introduced in series with resistor. Find the value of inductance and capacitance.
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23. A beam of electron is moving parallel to a beam of protons. What do you predict about their behaviour under different conditions? Explain by quoting the relations used.
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24. What is thermoelectric power? Show that it is independent of temperature of cold junction. How is thermoelectric power and neutral temperature related?
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25. An electron and a proton are possessing the same amount of K.E. Which of the two have greater de-Broglie wavelength? Justify your answer,
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26. Draw neat diagram of a telescope. Find its magnifying power. What is resolving power of a telescope? On what factors does it depend?
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27. What are radioactive tracers? Give its uses in agriculture and industries.
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28. Describe principle, construction and working of an A.C. dynamo.

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What is diffraction? What are its types? Explain the diffraction at a single slit.
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29. What are amplifiers? Describe the best PNF amplifier. Why is it best? To what use ampt are put to?
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30. A proton falls vertically downwards through a distance of 2 cm in a uniform electric field o magnitude 3.34 x 10³ NC^-1. Calculate
(a) Acceleration of proton falling down.
(b) Time taken by proton to fall through a distance of 2 cm and
© The direction of electric field.
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1. Why two electric lines of force never intersect each other?
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2. What is the difference between voltmeter and voltameter?
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3. Write down truth table for NOR gate.
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4. What is the use of control rods? Of what material are these usually made?
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5. Nature is using fusion reaction somewhere. Name it.
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6. What is meant by blue shift?
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7. Give two properties common to whole of e.m. spectra.
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8. What is solar cell?
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9. What is meant by dielectric polarisation ? Define dielectric constant of a medium.
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10. What is magnetic susceptibility? How does it vary in case of a paramagnetic substance?
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11. What is figure of merit? How is it determined?
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12. What is Seebeck effect and Seebeck coefficient?
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13. Range of an ammeter has to be increased N times. How can it be done?
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14. What is the ratio of gravitational and electrical forces of attraction between a proton and an electron?
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15. What are the conditions of sustained interference?
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16. State 2 main advantages and two disadvantages of semiconductors.
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17. Derive an expression for total work done in rotating an electric dipole through an angle 6 in a uniform magnetic field.
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18. What is Brewster’s law? What conclusions can be drawn from it?
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19. Derive an expression for a force on a current carrying conductor placed in a uniform magnetic field.
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20. A100 W, 250 V and a 50 W, 250 V lamps are connected in series. The combination is connected to 250 V supply. Which lamp will glow brighter? Justify your answer with proper calculations.
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21. You are having three mirrors fixed in the wall. Without touching these with anything, how can you say which one is plane, convex or concave?
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22. Positive terminals of 2 cells of 2 V, internal resistance of 1Ω and 1V, internal resistance 2 Ω are connected through 10 Ω wire, the negative terminals are connected through 8 Ω wire. The mid point of 10 Ω and 8 Ω wire are joined by 4 Ω wire. Find the current and P.D. across 4 Ω wire. Also find terminal P.D. across each cell.
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23. How can you derive the intensity at a point on neutral axis of a dipole? How the relation gets modified for small dipoles?
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24. How can the size of a star be determined from the knowledge of luminousuy of a star?
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25. What are elements of earth’s magnetic field? Define them. What is angle of dip on magnetic pole and magnetic equator? In which direction will a compass point in field free area?
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26. Describe Hertz experiment to confirm the existence of e.m. waves? Draw e.m. spectra.
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27. Four charges +q, + q, q, - q are placed respectively at the four corners of a square of side a. Find the magnitude and direction of electric field at the centre of the square.
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28. What are particle accelerators? Describe cyclotron. Why is cyclotron not suitable for accelerat¬ing electrons and neutrons?

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Two slits 0.125 mm apart are illuminated by light of wavelength 4500 A. The screen is 1 m away from the plain of the slits. Find the seperation between second bright fringe and 4th dark fringe.
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29. What is fusion and fission of nuclei? Can these be used for peaceful purposes? What were the maximum and least powers of nucelar devices exploded by India on 11th and 13th May 1998?
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30. What is Gauss’s theorem? Deduce the expression for electric intensity outside, on and inside a charged solid sphere.
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1. What is the difference between an ordinary electron and photoelectron?
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2. What is the function of starter in an electric motor?
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3. Give definition of ampere in terms of two wires carrying current placed at some distance.
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4. Define dipole moment in terms of torque experienced by it when placed in a unifoim magnetic field.
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5. On a resistor, body is marked red, edge blue and dot green and ring golden. What is the value of resistance?
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6. A capacitor blocks A.C., why?
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7. What would have been the colour of the sky in the absence of atmosphere?
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8. What are the units of conductance and conductivity?
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9. Give truth table of diagram given here.
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10. What are differences between Peltier effect and Joule effect?
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11. What is unit of capacity of a cell? Explain in 2-3 lines its significance.
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12. What is forbidden energy gap? What is its significance?
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13. What is quantization of electric charge 7 Explain it by giving two examples.
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14. Draw a set of three converging and a set of three diverging wave fronts.
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15. An electron is describing a circle in a magnetic filed of 10^-4 T. Calculate the frequency of revolution. Given the mass of electron = 9x 10^-31 kg and charge on the electron -
1-6 X 10^-19 C.
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16. Declination at a place is 2°E. Through what angle should the ship be steered with respect to north of the needle so as tq go towards west.
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17. What is Ampere’s circuital law? Derive it.
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18. If specific charge of proton is 9.6 X 10⁷ C kg^-1, find the specific charge of a-particle.
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19. Twelve wires each of 4 Q resistance are joined to form a skelton cube. Find the resistance across diagonally opposite corners of the cube.
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20. Draw a graph showing as to how the stopping potential varies with the frequency of the incident radiations. What does the slope of the line with frequency axis indicate?
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21. Derive a relation between the distance of object, distance of image, radius of curvature and refracting index for a convex refracting surface when a light is going from an optically denser to an optically rarer medium.
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22. What is Lenz’s law? Show that it is in accordance with law of conservation of energy.
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23. The phase difference between two waves reaching a point is Π /2. What is the resultant amplitude if the individual amplitudes are 2 and 4 mm respectively?
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24. What is radioactive fall out? What is its effect on human race?
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25. What are carrier waves? How can these be produced by a transistor?
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26. What are different types of spectra? How can the constitution of the material of the sun’s chromosphere be known from the study of sun’s spectra.
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27. A P.D. of V is applied across a conductor of length L, diamater D. How are the electric field E, the drift velocity vd and resistance R affected when (i) V is doubled ; (ii) L is doubled, (iii) D is doubled ?
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28. What is a solenoid? Derive an expression for the magnetic field inside the solenoid and at its edge.
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A double slit is illuminated by light of wavelength 6000A. The slits are 0 .1 cm apart and screen is placed 1 m away. Calculate (i) the angular positions of 10th maxima in radians (ii) separation of two adjascent minima.
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29. Describe tangent galvanometer. Give its theory and working. What are its disadvantages over moving coil galvanometer?
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30. Two small spheres of mass m, charge q each are suspended from a point by insulated threads each of length / and negligible mass. If 0 is the angle each makes with vertical when equilibrium
has been established. Show that q² = 16Π mgl² sin²θ tan θ.
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1. Define solar constant.
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2. Give two uses of polaroids.
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3. Why electric intensity inside a charged conductor is zero?
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4. Cyclotron is not suitable to accelerate electrons. Why?
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5. What is Zener voltage?
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6. What is de-Broglie wavelength of a particle of mass m at rest?
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7. What is the difference between mass number and atomic weight?
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8. What are full forms of QUASARS and PULSARS?
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9. A thin prism of 6° angle gives a deviation of 3°. What is the refraction index of the prism?
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10. What is de-Broglie wavelength of an electron accelerated across a potential difference V volt?
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11. Why is A.C. preferred to D.C.?
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12. What is meant by blue shift? What would have been the state of universe had there been blue shift? “
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13. What is capacitance of a conducting slab? Explain with reasoning.
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14. What is temperature coefficient of resistance? Name one substance each with positive, negligible and negative temperature coefficient of resistance?
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15. Find half life period of a radioactive material if its activity drops to (1/32) of its value of 37.5 years.
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16. Why does the sun appear reddish at the time of sunrise and sunset?
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17. Derive a relation for the energy stored in a capacitor,
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18. How can OR gate be realised from NAND gate.
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19. Eleven wires each of resistance 4 Q are joined to form an open skelton cube. Find the resistance across open end of the cube.
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20. What is drift velocity? Derive a relation between drift velocity and electric intensity.
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21. Derive an expression for fringe width in an interference pattern.
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22. What is transformer? Describe its working. Show that whatever is gained in voltages is lost in current and vice versa.
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23. Derive an expression for self inductance of a coil of n turns wound on a card board with iron core.
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24. A galvanometer has a resistance of 50 Q gives a full scale deflection for a current of 0.05 A. Calculate the length of a shunt wire required to convert the galvanometer into an ammeter of range 0-5 A. The diameter of shunt wire is 2 mm and its resistivity is 5 X 10^-7 ohm m.
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25. What are isotopes, isobars and isotones? Give one example each to illustrate your answer.
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26. Derive a relation for the distance which T.V. signals can directly be received from T.V. tower of height/?.
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27. What is angle of dip? Where is it 0° and 90°? How can you determine the angle of dip without placing dip circle in magnetic meridian?
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28. Describe a D.C. motor. What is the role of back e.m.f. in it? Determine the efficiency of a D.C. motor. When is it maximum?

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Define electric potential energy. Derive an expression for it on system of N point charges.
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29. Explain amplification action of a transistor. How a PNP transistor can be used as an amplifier with common emitter configuration 7 which one is preferred, a common base or common emitter amplifier? Give reasons for your answer.
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30. Describe Millikan’s oil drop method to determine the charge on an electron. What is the importance of electronic charge determination?
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1. What gate has the symbol shown in figure?
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2. What is non-ohmic resistance? Give one example.
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3. Define lumen.
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4. Define virtual value of current.
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5. What is the difference between focus and principal focus?
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6. What should be the properties of the material which should be used to make electromagnet?
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7. If a point charge q is rotated in a circle of radius r, what will be the work done when it has completed 2.5 rotations.
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8. What is difference between P.D. and e.m.f. of a cell?
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9. Show that the electric intensity is always perpendicular to the equipotential surfaces.
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10. What is drift velocity? How it is connected to current? Derive the relation, for the current in terms of drift velocity.
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11. How can you get a NOT gate by combination of NAND gates?
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12. Write down binary number of (583)₁₀.
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13. What is nuclear holocaust?
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14. Why moving coil galvanometer is preferred over moving magnet galvanometer? (five two important reasons).
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15. What are meteorites? .
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16. Define magnifying power of an Astronomical telescope when final image of a distant object is formed at least distance of distinct vision. Write down its value?
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17. Deduce an expression for electric intensity due to a line charge.
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18. Using Ampere’s circutal law, deduce magnetic field at the centre of a toroid due to current flowing in it.
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19. Deduce Ohm’s law and from its relation, number out the factors upon which the resistance of a conductor depends.
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20. What is half life period and average life period? Define disintegration constant. Given half life period of radium to be 1600 year and you have only one atom of radium. When will it disinte¬grate?
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21. A current entres a Wheatstone’s bridge consisting of P = Ω == R = 10 Ω and S = 11Ω. What is the current through galvanometer if its resistance is 100 Ω?
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22. What is Gauss theorem? Deduce electric intensity at a point outside, on and inside a spherical shell.
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23. A circuit contains L, C and R. Deduce the phase relationship between E and I.
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24. What are elements of earth’s magnetic field? How do these help us to get knowledge of earth field?
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25. An electron is accelerated. through a P.D. of 1000 V and directed into space between two parallel plates separated by 0 02 m with a P.D. of 100 V between them. If the electrons enter perpendicular to the electric field between the plates, what magnetic field perpendicular to both electron path and electric field will be necessary so that the electron may travel in a straight line?
Take e = 1.6 x 10^-19 C and m = 9 x 10^-31 kg.
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26. What is polarisation of light? What can be concluded towards the nature of light from it? What is Brewster’s law and what important conclusion is drawn from it?
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27. How can junction diode be used as full wave rectifier?
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28. On the basis of Bohr’s atomic model, derive relationship for radii of Bohr’s orbit and explain hydrogen spectra.

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A needle placed 45 cm from a lens forms an image on the screen 90 cm on the other side of the lens. Find its focal length. What is the type of lens? If needle is 5 cm long, what is the length of the image?
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29. What is magnifying power and resolving power of a microscope. Derive relationship for magnifying power of microscope.
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30. How can the field intensity on axial line of an electric dipole be deduced? How does the equation get modified for small dipoles? In what unit electric dipole moment measured?
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1. Define dielectric constant in terms of capacity.
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2. Is ‘dry’ cell a primary or a secondary cell
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3. Give the range of wavelengths of e.m. spectra sensitive to human eye.
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4. What is nuclear holocast ?
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5. What is approximately the value of specific charge of an electron in SI ?
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6. What is Albedo of a planet ?
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7. Define wavefront and a ray of light.
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8. Write down Biot-Savart’s law in vector form.
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9. What is Hubble effect ? What does this tell about universe ?
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10. What is Bohr magneton ? What is its value in SI ?
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11. What is critical angle ? How the earth appears to a fish in water ?
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12. Why ₉₂U²³⁸ cannot be used instead of ₉₂U²³⁵ in nuclear fission ?
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13. Identify the logical gate 1 and 2 in the logic circuit given. Also write down Boolean equation for the truth table for the combination.
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14. What is binding energy and the mass defect ? Whicbrnucleus has least binding energy ?
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15. What does an e.m. wave consist of ? On what factor does its velocity in vacuum depend ?
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16. What is Malus law ? What will be the intensity in the plane inclined at an angle of 60° ?
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17. Tips of an aeroplane are 20 m apart moving with a velocity of 720 km h-1 in earths field of
H = 0. 4 X 10^-4 T if the wings of the aeroplane are along E–W direction.
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18. Calculate the capacity of a capacitor when used in series with inductance of 5H will cause the circuit to resonant at 50,000 Hz.
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19. Why are the core of transformer laminated ?
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20. Derive an expression for average power of an A.C. circuit containing L, C and R.
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21. Derive an expression for capacitance of a parallel plate capacitor with a dielectric slab.
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22. A straight conductor 1 m long moves at right angles to both its length and a uniform magnetic field. If the speed of the conductor is 2 ms-1 ^{and strength of the field is 104 gauss find the value of induced emf in volt.
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23. What are microwaves ? To what use are these put to ?
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24. In Wheatstone’s bridge P = 1 Ω,Ω = 2 Ω, R = 2Ω, S = 3Ω. A galvanometer of resistance 4 Ωis put across B and C. A cell of emf 2 V and internal resistance 2Ω is connected across A and C. Find the current in unbalanced Wheatstone’s bridge.
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25. What is electron theory of magnetism ? Show how it explains the behaviour of a diamagnetic substance placed in magnetic field.
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26. Deduce the relation between the distance of object, distance of image, refractive indices and radius of curvature when light passes from an optically denser medium at concave refracting surface.
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27. Calculate resistance of 500 g of copper wire of diameter 0. 8 cm. Given the density of copper = 8 .9 g cm^-3 and resistivity of copper = 1.5 x 10 -6 ohm cm.
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28. Why is A.C. usually transmitted at high voltage ? Illustrate by considering an example. Why donot we transmit D.C. to distant station ?

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A stream of electrons moving with a velocity of 3 X 10⁷ ms^-1 is deflected by 2 mm in travelling through a distance of 0 . 1 m in the uniform magnetic field 18 V cm^-1 . Find the ratio of elm.
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29. How can a direct current be converted into very high frequency A.C? To what use is it put to? Explain by giving a neat and labelled diagram.
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30. What is nuclear fission and nuclear fusion? In which case more energy is produced? Discuss the effect of nuclear fall out.
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