» Class XII Model Test Paper : CBSE Sample Question Papers

1. Write the condition in which a transistor is saturated.
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2. Why a magnetic field is used to deviate cathode rays in a cathode ray tube and not an electric field?
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3. For a 60 W lamp, the luminous flux is 600 lumen. What is the luminous efficiency of the lamp?
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4. Why is the power of the objective lens in a telescope kept as small as possible?
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5. The ionization energy of H atom is 13.6 eV. What is the energy of the electron in the third Bohr orbit?
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6. In the 5 Ω resistor the heat dissipated is 10 joule/sec. What is the heat dissipated in 4 Ω, resistor?

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7. What is approximate half life of a proton?
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8. The energy of a photon is 42 eV. What is it momentum?
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9. What is reproduction factor in a nuclear chain reaction?
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10. Draw a labelled diagram of a fully charged lead acid accumator. What is its emf? What is the specific gravity of its solution?
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11. In a potentiometer using 2V for the determination of internal resistance of a 1.5 V cell, the balance point of the cell in open circuit is 76.3 cm. When a resistor of 9.5 Ω is used in the internal circuit of the cell, the balance point shifts to 64.8 cm length of the potentiometer wire. Determine the internal resistance of the cell.
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12. (a) Long distance radio broadcast use short wave bands, Why ?
(b) Optical and radio telescope are built on the ground but X-ray astronomy is possible only from satellites orbiting the earth. Why?
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13. In electrolysis of a solution of zinc sulphate, 2.04 g of zinc is deposited on the cathode in 50 min. If the voltage across the both terminals is 4.2 V, the solution resistance is 1.8 Cl, what is the e.m.f.?
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14. Write an expression for the thermo e.m.f. at a temperature difference between the junctions of a thermocouple. What are the basic characteristics of this e.m.f?
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15. When the plane surface of a planoconvex lens is silvered, it behaves like a concave mirror of focal length 20 cm. But when the curved surface is silvered it behaves like a concave mirror of focal length 7 cm. Draw diagram to show these constructions and find the value of refractive index of the material of the lens.
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16. Derive the formula for magnetic Lorentz’s force from Ampere’s formula dF = II x B. A positively charged particle with charge q enters per¬pendicularly in magnetic fields.
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17. Calculate the work done in deflecting a magnet in a uniform magnetic field and show that the work done in deflecting that magnet through 180° is 2μB.
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Find an expression for the energy density of electric field due to a point charge.
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19. Why conductivity of pure semiconductors increases with doping? Explain with the help of a diagram.
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20. A capacitor is charged and then discharged through an inductance. Find the equation of oscillations of charge and its frequency. Compare these oscillations with those of a mass-on-spring.
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21. Draw a circuit diagram of a fluoroscent tube with a choke and a starter.
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22. Show that when a conducting rod of length R moves with a frequency co with one end at the centre and the other at the circumference of a circular metallic ring of radius R about an axis passing through the centre of the coil perpendicular to the plane of the coil, the magnetic field B parallel to the axis, the e.m.f. induced is e = 1/2 BR² ω,
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23. State the inverse square law relating to photometry.
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24. Draw energy band diagram for sodium. Why there is no forbidden gap between the valence band and the conduction band?
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25. Discuss the method of measuring the distance of a celestial object by radar.
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26. Two parallel 320 cm conductors with equal currents are spaced at 8.7 cm and attracted with a force of 2.5 x 10^-2 N. Compute the current through the conductors.
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27. The voltmeter reads 120 V, what is its resistance?

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28. A loop of wire is placed in a uniform magnetic field. For what orientation of the loop is the magnetic flux maximum? For what orientation is the flux zero? Find an expression for the e.m.f. induced in the loop when it. Rotates with an angular velocity ω. Draw a graph between φ and t, (ii) between e and t.

A metallic rod is moved with constant velocity over a rectangular metallic frame placed in a magnetic field. Explain the following:
(i) How does an observer on earth explain the cause of the e.m.f. induced?
(ii) How did Faraday explain the cause of the e.m.f. induced? Write mathematical expressions for the above observers.
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29. (a) Give the principle of a Bimsen’s Grease spot photometer.
(b) Two lamps of 8 C.P. and 32 C.P. are placed 99 cm apart. Where should a screen be placed on the line joining them so that it is equally illuminated due to each lamp?
[(b) 33 cm from the 8 C.P. lamp in between the lamps or 99 cm from 8 C.P. lamp and 198 cm from 32 C.P. lamp outside both lamps]
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30. How can the electronic charge be determined from experiments on electrolysis and from Millikan’s experiment? Write the principles of these experiments.
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1. A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 60°. What is the torque needed to maintain the needle in this position?
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2. Give an example of wattless current.
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3. Why an electric iron with a thermostat used only with alternating current?
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4. What is self inductance of a coil in which current changes from 8 A to 2A in 3 x 10^-2 sec induces an e.m.f. of 2V.
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5. Amongst α, β and γ which one has the least: (i) penetrating power (ii) ionization power?
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6. The voltmeter reads 120 V, what is its resistance?
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7. Germanium crystal is to be made n type. What must be done?
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8. In what ratio will the intensity of the image increase when the diameter of the objective of an astronomical telescope is doubled? How will the resolving power change?
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9. Write an expression for energy density of a magnetic field assuming that there is no magnetic material inside the field. Compare this expression with the energy density of an electrastatic field.
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10. In a single slit diffraction, the slit width is 0.050 cm and the wavelength is 632.8 nm. How far from the centre maximum is the third order maximum on a screen 10 m away?
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11. Draw impedance diagram of an LRC circuit. Construct a similar diagram for a circuit in which the current frequency is doubled and the maximum emf is the same and find how the current will change as a result of this.
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12. Find the value of Rydeberg constant in Bohr’s Theory for hydrogen atom. Write its units.
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13. What is astronomical units? How can it be computed?
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14. How can deviation without dispersion be obtained with the use of two lenses, one of crown glass and the other of flint glass?
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15. How can eddy currents be minimised?
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16. The magnetic forces are very much smaller than the electric forces. Verify this statement.
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17. Draw a diagram to illustrate Young’s double slit experiment. The distance between the slits is d. Determine the maximal number of fringes that can be observed for a light of wavelength λ.
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18. The objective of telescope A has a diameter 3 times that of the objective of telescope B. (i) How much greater amount of light is gathered by A compared to B?
(ii) What is the ratio of ranges A and B?
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19. Two polaroids are placed at 90° to each other and the transmitted intensity is zero. What happens when one morepolaroid is placed between these two bisecting the angle between them?
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20. (a) If magnetic monopoles existed, how would Gauss law for magnetism be modified ?
(b) The earth’s core contains iron. Does this mean that earth’s magnetism is due to iron?
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21. Determine the speed of electron in the n = 3 orbit of Li⁺⁺.
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22. Calculate the first four energy states of a particle of mass m, moving freely along a length L and show these on a energy level diagram.
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23. Show that the kinetic energy of a charged particle does not change in a magnetic field.
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24. Why only coherent waves show interference?
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25. What is interference ? State the conditions of interference of light.
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26. What is depletion layer in ap-n-junction? Explain how is this layer formed.
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27. How can we obtain the mass of the milky way ?
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28. Show that the magnetic moment of a current loop is given by m = IA where / is the current in the loop and A its area.

How are small magnetic fields measured? Give the principle, theory and working of the apparatus used.
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29. A circuit consists of L and C in series joined to an a.c. Find the impedance.
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30. A metallic rod is moved with a uniform velocity over a rectangular frame placed in a magnetic field. Show that an e.m.f. is induced in it and find an expression for the work done.
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1. Name the electromagnetic radiation produced from transition in outer energy levels of an atom.
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2. What is the effect of doping in a pure semiconductor?
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3. Draw graphs showing variation of output voltage with current in load for unregulated power supply and regulated power supply.
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4. A capacitor of capacitance 2µF is charged to 200 V. It is now discharged through a resistance of 2 Q, what is the heat produced in the resistance?
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5. An a.c. source is 120 V - 60 Hz. What is the voltage after 1/720 sec from the time the sine curve of a.c. starts?
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6. Name two superior and inferior planets?
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7. Define thermopo wer of a thermocouple.
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8. What is the magnetic moment of an atom of a diamagnetic?
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9. Draw an approximate graph showing change in resistivity of metals with the rise in temperature from OK to sufficiently above the room temperature. Why there is resistivity even at 0 K?
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10. (i) Write the formula for the power of an alternating current. What is power factor?
(ii) What is a wattless current?
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11. Find the potential difference between the points a and b.
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12. A convex lens of focal length 20 cm and a concave lens of focal length 10 cm are arranged a distance apart. A parallel beam of light falls on the convex lens and leaves the concave lenses as aparallel beam. What is the distance between the lenses?
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13. In a hydrogen spectrum the frequency for transition n_i =3 to n_f = 2 is v and for transition 3i = 2 to n_f = 1 is 121.5 nm is v’. What is the frequency for transitions ni = 3 to n_f =l?
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14. Derive a relation between the apparent depth and real depth of objective in denser media.
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15. The voltage across the terminals of a battery of emf falls from 12 V to 10 V.
Find the silver plated at the cathode in 30minutes. Given internal resistance of the battery as 2Ω and atomic weight of silver 108 g/mole.
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16. Derive the mathematical expression for surface temperature of a planet in solar system.
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17. What is the potential difference V_a - V_b in the circuit shown. Image
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18. Three point charges - 4q, q and - q are placed in a straight line of length l at point o, l/2 and I respectively. What is the net force on the charge _ q?
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19. The number of alpha particles emitted per minute by a small amount of a radioactive substance was 560 initially and 280 after 2 hours. What is the expected rate of emission after another four hours?
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20. Explain how the process of avalanche breakdown occurs in a pn junction diode? How is it different from Zener breakdown?
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21. Why a converging lens can never form a point image of a distant point source? If D is the distance from the lens at which the light is focussed. Write the expression for the radius of the first dark ring in the image. Describe the change in width of the central maximum of the single-slit diffraction pattern as the width of the slit is made smaller.
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22. A wire is bent into the shape shown in Fig. (a) and the magnetic field is measured at Pi, when the current is I. The same wire is bent into the shape of a chord shown in Fig. (b) and the magnetic field is measured at P₂ with the same current /. If the total length of the wire is the same in each case, what is the ratio of B₁ / B₂?
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23. What are the limitations of the Huygen’s wave theory of light? A spherical wave of light falls on a concave lens. Draw a diagram to illustrate the refraction of the wave.
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24. What is magnetic flux? Give its dimensions. Differentiate between magnetising field H and magnetic field B. Write the expressions for their line integrals.
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25. Explain the principle of a potentiometer. Two potentiometers of equal resistance and length I, are connected in series and their sliding contacts are connected. In one potentiometer the sliding contact is kept fixed at the mid point How will the reading of me ammeter vary as the sliding contact of the second potentiometer is moved from one end to me other?
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26. Explain an approximate characteristic curve of a p-n junction diode.
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27. A lens forms a sharp image on a screen. A parallel sided transparent slab of refractive index (X is introduced between the lens and the screen. The image is disturbed and to refocus, it is found necessary to move the screen by a distance. In which direction the screen be moved? What is the thickness of the slab? Derive the expression.
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28. Explain the principle of an ac generator. When large current is drawn from an ac generator me frequency falls. Why?

How can a NOT gate be realised in practice? Draw a circuit diagram and explain with the help of truth table.
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29. Define work function of a metal. Explain how work function can be found from the experiment on photoelectric effect.
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30. A fluoroscent lamp taking 80 W at power factor 0.7 lagging from a 230 V, 50 Hz supply is to be corrected to power factor 1.0. Determine the value of the capacitor used.
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1. In a Young’s double slit experiment the intensity of bright fringe is I. If the slits have the same width what is intensity due to one slit only?
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2. Which temperature is higher in the graphs?
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3. Two large conducting plates are arranged parallel to each other. One of the plates is given a charge + Q. What are the charges induced on the surfaces of other plates?
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4. Give the name of the source and the spectral range of the following wavelengths of the electromagnetic spectron: 5800 A, 200 m, 0.6 A and 1200 A.
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5. Write the truth table for the combination of the gates.
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6. An electron is moving vertically downwards. If it passes through a magnetic field which is directed from south to north in a horizontal plane then in which direction the electron would be deflected?
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7. When the switch S in turned off which bulb will die out promptly?
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8. A lens of focal length/forms the image of a luminous object on a screen. The image is n times enlarged. What is the distance of the screen from the lens?
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9. Draw approximate equipotentials for a negatively charged metallic sphere.
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10. Under which’ of the following two cases more work has to be done in moving further apart the plates of a charged capacitor and why?
(i) the charging battery remains connected to the capacitor.
(ii) after charging the capacitor the battery is removed.
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11. Describe an experiment to verify the second law of electrolysis.
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12. Draw lines of force for a bar magnet placed in a horizontal plane with its axis in the magnetic meridian N →N.
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13- The magnetic field B at the centre of a ring with current 11 A is found to be 120 x 4π x 10^-7 T. Find the diameter of the ring.
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14. Can the primary and secondary of a transformer be interchanged to connect it from a step up to a step down transformer and vice versa? Why?
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15. Explain two different methods with necessary electrical connections to light up a 100 W, 15 volt bulb by a 220 V - 50 Hz a.c. source. In which of the two methods more energy is dissipated and why?
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16. Light of wavelength 2000 A falls on an aluminium surface. In aluminium 4.2 eV are required to remove an electron. What is the K.E. of (a) the fastest electron (b) the slowest electron © what is the stopping potential? (d) What is the cut-off wavelength?
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17. Distinguish between natural and artificial radioactivity. Find an expression for activity at time I in terms of half life of a radioactive substance.
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18. Draw an energy band diagram for sodium chloride.
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19. The capacitors shown are of equal capacitances joined in series with a battery of 10 V. The point B is earthed. Find the potential of A and C.
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20. Determine (i) the potential of A (ii) the potential of/). (iii) reading of the voltmeter connected across 16 V battery,
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21. Distinguish between See back effect and Joule effect. A150 Ω electric heater can carry a maximum current of 1.1 A. It is to be operated on a 220 V line, what is the minimum resistance required in the circuit?
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22. Two alternating emfs of peak values 8 V and 6 V and frequencies 50 Hz and 100 Hz respectively are fed in a circuit containing a resistance of 7.07 Ω. What is the rms current in the circuit?
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23. A thin sheet of glass (µ- 1.5) of 6 |om thickness is interposed in one of the beams of the Young’s double slit experiment. This results in the shifting of the zeroth fringe to theposition occupied by the fifth fringe. What wavelength of light is used?
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24. For what value of wavelength of light our eye is most sensitive? What is the value in lumen/watt corresponding to this wavelength? Explain with the use of a graph.
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25. Define luminuous intensity of a light source and illuminance of a surface. How does the intensity of illuminance of a surface depend upon its distance from a light source? Explain.
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26. State the three factors on which the focal length of a lens depends. The distance between an object and a screen is d. A convex lens of focal length /is placed between the object and the screen. What should be the minimum value of d so as to obtain the image of the object on the screen.
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27. How can the surface temperature of earth be found theoretically from Stefan Boltzmann law?
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28. A particle of charge q and mass m moves along a circle of radius r under the action of a magnetic field B. An electric field is suddenly switched on and it is observed that the particle begins to move with a uniform velocity along the tangent to the circle. Find the magnitude and the direction of the electric field.

Explain with the help of a suitable diagram the net torque acting on a rectangular loop carrying a current and placed in a magnetic field.
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29. Explain critical mass and controlled chain reaction in reference to a nuclear reactor clearly indicating in a diagram (i) the moderator (ii) coolant (Hi) control rods.
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30. What are the methods of finding Plank’s constant h? State how work function of the cathode can be determined from the photoelectric effect?
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1. Name the physical quantity which has Am² as unit for measurement.
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2. Differentiate between ionization energy and work function of a metal.
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3. Can we accelerate a charge in a magnetic field?
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4. Define voltage sensitivity of a galvanometer.
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5. Draw the symbol for a cell and show the sense of e.m.f. in it.
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6. Two protons of a nucleus are 6.0 x 10^-6 m apart calculate their mutual potential energy.
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7. State one reason why magnetic forces are stronger than the electrostatic force in current carrying conductors.
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8. What is approximate half life of a proton?
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9. How many spectral lines are emitted by a hydrogen atom that is excited to nth stationary state.
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10. Derive an expression for the current flowing in a conductor in terms of the drift velocity of charge carriers.
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11. A steel wire of length / has a magnetic moment M. It is bent into a semicircular arc. Will the magnetic moment change? What is the new value?
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12. What are slow neutrons? Why heavy water (D2O) is used as a moderator to slow down neutrons?
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13. Two point charges q¹ and q² are situated at points A and B. The charge q¹ is surrounded by a metallic shell. What is the force on q¹? What is the force on q²?
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14. In the circuit shown if G reads zero, what is the value of R?
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15. Find an expression the time period of an oscillating magnetic needle in a uniform magnetic field.
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16. What are the currents in 1 Ω coil and 5 Ω resistance at t = 0 when the switch is just pressed ?
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17. With the use of a suitable diagram show how the sun even below the horizon can be seen sometimes.
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18. If in a Rutherford’s experiment the α particle scattered at 90° be 28 per minute. Find out the number of particles scattered at 120°?
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19. What is the principle of measurement of internal resistance of a cell? When the resistance between a and b is 36 Ω and the cell e has emf 1.5 V, there is no current in the galvanometer. When this cell is replaced by an unknown emf, the resistance between a and b is 48 Ω for no current in the galvanometer. What is the value of unknown emf?
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20. Draw the logic symbol of NAND gate. Describe its realisation.
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21. Derive a relation between polarising angle and critical angle of a transparent substance drawing suitable illustrative labelled diagram.
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22. What is a superior planet? How its distance from sun be determined?
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23. State Joule’s law for dissipation of heat in a conductor. Why fuse wire used for heavy current must be thicker than that used for small currents?
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24. The power of a lens is 3 D. When immersed in a liquid its power is- 2 D. If the R.I. lens is 3/2. What is the R.I of the liquid?
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25. What are limitations of a transistor amplifier as a cut-off transistor and as a saturated transistor?
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26. What is the angle of deviation θ if the charged particle of mass m and charge q enters the magnetic field perpendicular to its velocity v. The width dof the region of the magnetic field is smaller than (i) mv/2qb (ii) 2 mv /pb (iii) mv/ qb .
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27. The intensity of light due to one slit in a Young’s double slit experiment is twice the intensity of light due to the other slit. What is the ratio of maximum intensity to minimum intensity in the interference fringe pattern?
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28. How a rainbow is seen during the rainy season? Illustrate your answer with suitable diagrams.

Find the condition for formation of first dark ring due to light diffraction by a circular aperture of diameter d.
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29. What are the relative merits of common base, common emitter and common collector transistor amplifiers? How does the voltage gain of an amplifier differ from its current gain?
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30. Why the plates in Millikans oil drop experiment be kept exactly parallel and horizontal? Derive an expression for the radius of an oil drop falling with a terminal velocity u. Use this expression to find e when the drop moves upward with a terminal velocity v.
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1. Write relation between E and V at a point in an electrostatic field.
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2. What is the resistance of an intrinsic semiconductor at 0 K?
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3. Two inductances carry currents that vary with time as shown. In which the induced e.m.f. will be larger?
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4. What is net force on a loop of area A carrying current i and placed in a uniform magnetic field B?
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5. Write the truth table for A + B where A and B are the inputs. Name the gate.
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6. Very distant stars not visible to the naked eye are visible through a telescope. Why?
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7. What is the phase difference at the point of observation where two coherent sources produce a dark fringe?
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8. Light of two different frequencies whose photons have energies 1 eV and 2.5 eV respectively illuminate succesively a metal of work function 0.5 eV. What is the ratio of maximum speeds of emitted electrons.
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9. Two parallel metal plates, each with area A carry charges Q1 and Q2. Determine the intensity of electric field as a point outside the plates, at a point inside the plates.
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10. When 1 gram of hydrogen (e.c.e = 1.044 x 10^-8 kg/C) forms water, 34 kcal of heat is liberated. What is the minimum voltage required to decompose water?
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11. A long straight wire carries a current i. An electron moving with a uniform speed v is at a distance r from the wire. Find the duration and magnitude of die force acting on the electron if its velocity is directed (i) towards to wire (ii) parallel to the wire.
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12. Write the principle of a vibration magnetometer. The period of oscillation of thin bar magnet is Tsec. It is broken into two halves of half length. What is the period of oscillation of each half?
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13. What is susceptibility and reteutivity of a ferromagnetic? Why soft iron is used for electromagnets?
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14. A ray of white light strikes obliquely on a rectangular slab of glass. Draw diagram to illustrate that no dispersion is possible.
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15. An angular magnification of 30 is desired using an objective of focal length 1.25 cm and an eye piece of focal length 5 cm. How will you set up the compound microscope?
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16. Distinguish clearly between magnifying power and resolving power of a telescope and establish a relation between the two.
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17. What are the various difficulties in achieving nuclear fission chain reaction in natural uranium and how these have been over come?
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18. Define the terms excitation potential and ionisation potential of an atom.
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19. How can a potentiometer be calibrated to read directly small emfs?
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20. Find the current in the circuit as measured by the ammeter.
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21. A circular loop of radius r carries a current i. Another circular concentric loop of smaller radius a is held perpendicular to it. What is the torque acting on the smaller loop if it carries a current I.
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22. Draw a sketch showing the variations of X_L, X_c and Z with changes in the angular frequency of a.c. fed to an LRC circuit.
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23. State Faraday’s law of electromagnetic induction for a magnetic field varying with time in the integral form.
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24. In a double slit experiment, what should be the width of each slit to obtain 10 maximas of the double slit within the central maximum of the single slit pattern. λ = 500 nm.
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25. Draw a diagram of energy bands in a pure semiconductor at 0 K and at room temperature. What will happen to the number of electrons in the conduction band as the temperature of the material is increased further?
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26. Why some regions in Milky way appear dark?
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27. (i) Why collector voltage is held constant while determining the common-emitter current gain by making small changes in direct current ?
(ii) Why CE amplifier has a higher current amplification as compared with a CB amplifier?
(iii) Why input and output signals of a CE amplifier are always out of phase?
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28. What are coherent sources of light? Explain why two incoherent sources cannot produce a sustained interference.

Draw a diagram to explain the formation of image of an extended object due to a concave lens and hence derive a formula for transverse magnification.
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29. A capacitor is charged and then discharged through an inductance. Find the equation of oscillations of charge and its frequency. Compare these oscillations with those of a mass-on- spring.
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30. Calculate the release in energy in MeV from the nuclear reaction
¹⁰₅B + ¹₁H → ¹¹₅B + ¹₁H
Given mass of boron (¹⁰₅B) = 10.01605 au
mass of boron (¹¹₅B) = 11.01286 au
maas of ²₁H= 2.0142 au
maas of ¹₁H = 1.00812 au
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1. A capacitor of capacitance C is charged to a potential V. What is the net flux of electric field through a closed surface enclosing the capacitor?
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2. Write the equation of a plane electromagnetic wave travelling along the 7-axis.
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3. Name a planet which has no satellites.
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4. A resistor has a colour band sequence: gray, blue, gold and gold. What is the range in which its value must lie?
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5. A tangent galvanometer is joined to an ideal battery. What is the change in the angle of deflection if the number of turns in the coil is doubled?
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6. What is the range of the waves that are transmitted by direct line of sight using tall towers and rebroadcasted from another place?
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7. Why aluminium wires are prefered for ova: head cables?
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8. Two cells each of emf e and internal resistance r1 _{and r2 are joined in series through a resistance R. A voltmeter across the cell of resistance ft reads zero. What is the relation between R, r1 and r2?
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9. What is apotentiometer? Given a 3.0 V potentiometer. Draw a circuit for calibrating a voltmeter in the range of 0.5 to 2.5 V.
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10. State Doppler effect in light.
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11. Name the three types of absorption spectra? State under what condition the band absorption arises?
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12. Use the mirror equation to deduce that an object placed between/and 2f of a concave mirror produce a real image beyond If.
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13. Obtain an expression for the magnitude m of a star in terms of its apparent brightness.
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14. A small sphere with charge +q₂ is enclosed by a spherical shell of charge +q₂ and q₂ > q₁. The two are connected by a wire. How will the charges move? Use Gauss law to explain.
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15, State one difference between a primary cell and a secondary cell. Which type of cell would you like to use if your device required (i) a current of 100 A for 20 s? (ii) a current of 10 m A occasionally ?
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16. A voltmeter has a resistance G and range 0—10 V. It is to be converted into a voltmeter of range 0—100 V. What resistance is to be used in series? Show the necessary formula. Answer

17. In the following graph of the photoelectric effect between the frequency and the kinetic energy of the photoelectrons what is:
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(i) The maximum kinetic energy of the electron emitted by the light of 8 x 10¹⁴ Hz.
(ii) Work function of the cathode metal.
(iii) Planck’s constant.
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18. Draw a circuit for a transistor (NPN/PNP) CE amplifier. Why we use silicon transistors and not germinium transistors in the above amplifier?
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19. Two bulbs rated 25 W—220 V and 100 W—220 V are joined in parallel to 440 V supply. Which bulb will fuse?
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20. Write the output waveform for the gate shown in figure.
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21. Why does the damping of the motion of the coil in a moving coil galvanometer depend on the resistance of the external circuit? Derive an expression to illustrate your answer. Why the galvanometer coil stops when its terminals are short circuited?
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22. A proton with kinetic energy 10 eV, moves in a circular path in a uniform magnetic field. What is the kinetic energy of (0 a-particle and (ii) deutron moving on the same path in the same field? Answer

23. What is a choke coil? An electric lamp which runs at 100 V d.c. and 10 A current is to be connected to a 220 V, 50 Hz line. What choke is required? Answer

24. The focal length of a convergent lens (µ= 1.5) in air is 20.0 cm. What is its focal length in water µ= 4/3?
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25. Both U²³⁵ and Pu²³⁹ are fissile but Pu²³⁹ is used more, why?
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26. Explain why an LC tank circuit once excited does not produce sustained oscillations. Draw a circuit diagram of an oscillator showing how transistor is biased and how the positive feedback takes place in the circuit.
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27. State the laws of refraction of light. A microscope is focussed on a mark. Then a glass slab of refractive index 1.5 and thickness 6 cm is placed on the mark. To what distance the microscope should be moved to get the mark again in focus?
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28. Obtain an expression for the velocity of electron in a hydrogen atom.
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29. Derive an expression for the force on a surface charge. A sphere of radius 10 cm is charged to a potential of 3000 V. What is the force per unit area on its surface? Take Eo = 9 x 10^-12 C²/Nm².

Derive an expression for energy stored in a capacitor per unit volume in terms of the electric field.
Two parallel plate capacitors of capacitances C and 2 C are connected in parallel and charged to apotential difference V. The battery is then disconnected and the regions between the plates of the capacitor C is completely filled with a material of dielectric constant K. What is the potential difference on the combination?
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30. A circuit is composed of a resistance to which an a.c. V = Vo sin ωt is applied. Show that the current is given by I = Vo /R sin ωt. Plot the phase of the e.m.f. and the current and show that they are in phase. What is the impedance of the circuit?
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1. What is the capacitance between the point A and B.
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2. What is the equivalent resistance of the circuit?
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3. Do all thermocouples have neutral temperature?
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4. If the horizontal and vertical components of earth’s magnetic field are equal at a place what is angle of dip?
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5. When the switch is closed what is the direction of the current in loop B as seen Perpendicularly? What is the direction of the current if the switch is now opened?
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6. What is the significance of 3K radiation?
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7. The critical angle for the material of the prism is 45°. Show the emergent ray in the diagram.
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8. What is an astronomical unit?
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9. A particle of mass m and charge q is thrown against a uniform electric field £ with or speed v. What distance it travels before coming to rest? Will it continue to remain at rest?
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10. How can mass of an electron be found?
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11. Write Maxwell’s equation and the Lorentz’s force law and show that these are dimensionally consistent.
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12. A metallic wire is given a shape of a right angled triangle of height / and moved in the plane of paper in a uniform magnetic field B as shown with a uniform velocity v.
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(i) What is the em/induced in the loop abc (ii) in the part ac (iii) in the part be (iv) in the part ab.
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13. Two stars A and B have their magnitudes +3 and +4. Which stars look brighter? Find the ratio of their brightness.
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14. Light is incident from glass (µ= 3/2) to water (µ = 4/3). What is the range of angles of deviation other than the minimum deviation?
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15. Draw a ray diagram for near point vision of the image of a distant object seen from an astronomical telescope. Write the expression for the length of the tube in near point vision.
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16. Define the terms (0 threshold wavelength and (ii) slopping potential in a photoelectric experiment. What is the range of kinetic energies of photoelectrons emitted in the experiment?
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17. What is the need of adding impurity to an intrinsic semiconductor? In a N-type semiconductor does it take more energy for a valence electrons to excite thermally, or to librate an electron from the impurity atom?
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18. What is a light year? How is it related with astromical unit?
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19. Why voltmeter, ammeter methods of measuring resistances are unsatisfactory?
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20. If a current of 10 mA exists in 2 kΩ resistance. What is the potential difference between A and B? What is the current in the other three resistances?
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21. A magnetic dipole is under the influence of two magnetic fields. The angle between the field direction is 60° and one of the fields has magnitude of 1.2 x 10^-2T. If the dipole comes to stable equilibrium at an angle of 15° with the field, what is the magnitude of the other field?
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22. Three parallel straight long conductors are located in air at equal distance (15 cm) from each other lying on the vertices of an equilateral triangle. The conductors carry equai currents 12 A. Two currents points downwards and one upward. Calculate the B field at the centre of the triangle.
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23. What is diffraction of light? At what distance from a slit of width a the effects of diffraction of light are clearly visible when the slit is shined with light of parallel rays of wavelength λ?
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24. A lens system is composed of two lenses in contact, one plano¬concave and made of flint glass and another double convex and made of crown glass. The radius of common face is 0.20 m and the radius of the other face of the crown lens is 0.12 m. Find the focal length of the system.
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25. What are the differences and similarities in the following?
(a) Positron and proton
(b) Neutron and neutrino
© Neutron and proton.
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26. What is the value of the emitter current in the circuit? What is the collector voltage?
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27. How can a NAND gate be made by a NOT gate and an AND gate? Draw the combination, symbol and truth table for this.
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28. Show that the component of velocity of a charged particle along the direction of the magnetic field does not change.

A loop is situated in a uniform and constant magnetic field. Describe how an e.m.f. can be induced in the loop in this situation.
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29. Starting from the equation of an a.c. current find an expression for its RMS value.
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30. What is photoelectric emission? Why wave theory of light is unable to explain this effect?
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1. In a plane at 45° to the magnetic meridian the apparent dip is 30°. What is the true dip?
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2. When the plates of a charged parallel plate capacitor are brought closer to each other, how will their potential difference change?
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3. Differentiate between e.m.f. and potential difference in an electric circuit?
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4. Draw a typical magnetisation curve for a ferromagnetic para/dia magnetic material.
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5. What is 21 cm electromagnetic radiation? To which part of the em spectrum it belongs.
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6. Write the expression for the frequency of the AC output from an RC oscillator.
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7. The reading of the galvanometer G in the figure is zero. Calculate the value of R.
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8. Write the approximate orbital period of Venus.
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9. A positive charge q is placed in front of a conducting solid sphere at a distance r from its centre. Is there any electric field at the centre of the sphere due to the charges appearing in its surface? If so calculate the magnitude and direction of the field.
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10. A capacitor is charged by connecting it to a battery through a resistance. Find expressions for the energy stored in the capacitor and for the energy dissipated as heat in the resistor at any instant.
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11. In an electroplating experiment m gram of silver is deposited with 4A of current flow for 2 minutes. What is the amount of silver deposited by 6A in 40 sec?
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12. Each resistance in the network shown is r. What is the equivalent resistance between the points a and b.
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13. Along wire is bent so as to form a right angle at the middle. A current i is passed through the wire. What are the magnitudes of the magnetic fields at a and b?
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14. Why power is transmitted at very high voltages?
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15. A compound microscope of tube length 6,5 cm has a magnifying power of 100 when the finai image is formed at infinity. The focal length of the eye piece is 2 cm. What is the focal length of the objective?
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16. A converging lens of focal length 12 cm and a convex mirror of focal length 7.5 cm are placed 5.0 cm apart with their axes coinciding. An object is placed 60 cm from the lens away from the mirror. Where is the image formed? Answer

17. Show by diagrams the motion of a positive and a negative particle entering a magnetic field perpendicularly.
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18. Give a method of determining the size of a star.
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19. Give an explanation for ferromagnetic behaviour of substances? How is it different from paramagnetism?
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20. In the circuit shown a voltmeter reads 3V when connected across 1500 Ω. What is the resistance of the voltmeter?
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21. What is the function of a starter in a heavy motor?
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22. In Young’s double slit experiment, how coherent sources are obtained? State
(i) The colour of the central bridge
(ii) The colour of the fringe next to central fringe when the above experiment is performed with white light. Why no completely dark fringe is obtained in this case.
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23. In a plane electromagnetic wave passing through space, write the expressions for (i) elecric field (ii) magnetic field (iii) electrical energy density
(iv) magnetic energy density. What is the frequency of electrical energy density?
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24. A beam of light propagates through a medium 1 and falls onto another medium 2 at an angle a. After that it propagates in medium 2 at an angle p. The wavelength of light in medium 1 is λ, what is the wavelength in medium 2?
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25. In a hydrogen spectrum find the wavelength that lies between 618 nm and 700 nm.
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26. Draw a logical circuit showing A , B + A . B and write its truth table.
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27. What is a saturated condition of a transistor? Under what conditions a transistor is saturated? Draw a CE characteristic in output circuit and show the saturated part of the characleristies.
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28. What is neutron separation energy V Obtain its value for ₂₉Ca⁴¹.

How can the emission of p particles be explained? Why all nuclei do not emit β particles? Which element has the most stable nucleus? Why then not ail nuclei degenerate into that element?
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29. Describe Bohr’s theory of Hydrogen atom and find the expression for the frequency of 2nd line of Baimer series.
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30. In Geiger Marsden experiment define the terms, inpact? parameter, and the distance of closer approach. Illustrate your answer. A proton coming from infinity hits a proton at rest. The impact parameter is zero. The velocity v of the hitting proton is in the straight line connecting the centres of protons. The mass of the proton ism. Find the distance of closest approach.
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1. A copper strip AB and another iron strip AC are joined at A so as to form a junction A. The ends B and C are kept free. The junction A is kept at 0°C and both B and C are at 100°C. Is there a potential difference between B and C? Answer

2. A charge Q is placed at the centre of the open end of a hemispherical surface. What is the flux of the electric field due to this charge through the surface of the hemisphere?
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3. The light coming from an electric bulb is falling normally on a small surface. If the surface be now inclined by 60° from this position, in what ratio will the illumination of the surface change?
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4. An inductor coil when joined to a 5 V battery draws a current of 10 A. The coil is joined in series with a capacitor and an a.c. source of 5 V rms. There is no phase difference between the current and the voltage across the circuit. What is the rms current in the circuit?
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5. What is the ratio of energies of wavelength of 0.01 A and 0.5 A radiations?
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6. The earth’s magnetic field is 3.4 x 10-5 T at the magnetic equator of the earth. What is its value at the earth’s magnetic poles?
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7. When a p-n junction is reverse biased the constant current is 20 μA. When it is forward biased at 100 mV, a current of 80 μA is obtained. What is the diffusion current?
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8. The angle of maximum elongation for Venus is found to be 47°. What is the Venus Sun distance and Venus Earth distance?
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9. A parallel plate air capacitor has a capacitance of 25 pF. What is the potential across the capacitor and the energy stored when the capacitor is charged to 0.60 µC? If without permitting the charge to escape; one increases the separation between the plates to three times its original value, what are the new values for C, V and the stored energy? How much work was done on the capacitor during plate separations?
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10. What are the currents through the resistances in the circuit shown in figure?
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11. Define a Faraday and Faraday constant.
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12. Yellow light of wavelength 6000 A passes from air to water. What is the frequency of this light in water? What colour will be perceived by a diver in water?
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13. Explain reproduction factor of nuclear chain reaction.
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14. A wire of length 10 cm lies on the principal axis of a concave mirror of focal length 10 cm in a manner that end closer to the pole is 20 cm away from it. What is the length of the image of the wire?
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15. Define solar constant. Give any two uses of this parameter.
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16. Derive an expression for the magnetic field on the axis of a toroid.
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17. How is a choke coil connected in a fluorescent tube circuit ? What would happen if the choke coil is not used? Can a capacitance be used in place of the choke coil? Explain with necessary expressions.
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18. Two resistances R and 2R are connected in series and in parallel respectively in an electrical circuit, whatis theratio of thermal energy developed in R and 2R in the cases?
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19. Can you explain why a test tube immersed at a certain angle in water appears to have a mirror surface for a certain viewing position? Draw a labelled diagram to illustrate your answer.
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20. Draw an energy band diagram for a copper crystal showing the valence band and the conduction band and explain how copper is a conductor of electricity?
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21. What is dispersion? How is it caused? Differentiate between line and continuous emission spectra.
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22. In the potentiometer circuit shown the potentiometer wire is 560 m long. What is the length AC for no deflection in the galvanometer?
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23. Give strong points in any theory of earth’s magnetism. Give relation between the different components of earth’s magnetism.
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24. Show that the magnetic moment of a bar magnet is given by product of its length and pole strength. Calculate the magnetic field at a point due to a bar magnet of magnetic moment m in the end-on position.
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25. The width of the central maxima in a single slit experiment is 4.0 cm when light of 589 nm is used. What will be the width if light of 436 nm is used? Answer

26. Show how any logical gate can be constructed by using only NAND gates or only NOR gates.
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27. Draw an approximate binding energy per nucleon curve and explain its behaviour on the basis of short-range nature of nuclear forces.
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28. (i) Two metal spheres of capacitance C1 and C2 are charged put in contact and then separated. What is the ratio of the charges on them?
(ii) Find an expression for the capacitance of a metal sphere of radius R.
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29. A loop of wire is placed in a uniform magnetic field. For what orientation of the loop is the magnetic flux maximum? For what orientation is the flux zero? Find an expression for the e.m.f. induced in the loop when it rotates with an angular velocity ω. Draw a graph (i) between Ø and t. (ii) between e and t.

A metallic rod is moved with constant velocity over a rectangular metallic frame placed in a magnetic field. Explain the following:
(i) How does an observer on earth explain the cause of the e.m.f. induced?
(ii) How does an observer on the rod explain the cause of the e.m.f. induced?
(Hi) How did Faraday explain the cause of the e.m.f. induced 7?
Write mathematical expressions for the above observers.
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30. Describe Millikan’s oil drop experiment to find the value of electronic charge. How is the radius of the oil drop is determined? Find the expression for q in terms of radius and an expression for radius of the oil drop.
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