» Class XII Sample Question Papers : CBSE Sample Question Papers

Q. 1. What is the role of MnO2 in a dry cell?
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Q. 2. Define a lumen.
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Q. 3. A wire of resistivity p is stretched to three times its length. What will be its new resistivity?
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Q. 4. An electron, moving with a velocity 10⁷ ms^-1, enters a uniform magnetic field of IT, along the directions of the field. What would be its trajectory in this field?
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Q. 5. How does the resolving power of a telescope change when the aperture of its objective is increased?
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Q. 6. Suppose there existed a planet that went round the sun twice as fast as the earth. Will its orbital radius be more than or less than that of the earth?
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Q. 7. An electric lamp connected in series with a capacitor and an a.c. source is glowing with certain brightness. How does the brightness of the lamp change on reducing the capacitance?
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Q. 8. An equiconvex lens of focal length 15 cm is cut into two equal halves as shown.
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What is the focal length of each half?

Q. 9. What is meant by red shift? What does it tell about the universe?
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Q. 10. What is the name given to the curves the tangent to which at any point gives the direction of the magnetic field at that point? Can two such curves intersect each other’.’ Justify your answer.
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Q. 11. Write two points of difference between interference and diffraction pattern of light.
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Q. 12. Calculate the refractive index of material of an equilateral prism for which the angle of minimum deviation is 60
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Q. 13. If a ‘compass box’ and a’ dip circle’ were to be taken to the magnetic north pole of the earth, what would one observe with regard to the deflections of their respective needles and why?
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Q. 14. A circular brass loop of radius ‘a’ and resistance R is placed with its plane perpendicular to a magnetic field which varies with time as B =Bq sin (at. Obtain the expression for the induced current in the loop.
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Q. 15. How would the following be affected in the absence of atmos¬phere around the earth?
(a) Surface temperature of the earth.
(b) Range of radio wave transmission.
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Q. 16. A microscope is focussed on a dot at the bottom of the beaker. Some oil is poured into the beaker to a height of Y cm and it is found necessary to raise the microscope through a vertical distance X cm to bring the dot again into focus. Express the refractive index of oil in terms of X and Y.
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Q. 17. The energy of an electron in the nth orbit is given by En - - 13.6/n2 (eV). Calculate the energy required to take the electron from the ground state to the second excited state.
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Q. 18. Identify the logic gates 1 and 2 hi the logic circuit given below. Also write the truth table for the final output for all possible combinations of the inputs A and B.
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Q. 19. With the help of circuit diagram, explain how would you compare the e.m.fs of two primary cells using a potentiometer.
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Q. 20. What is rectification? With the help of a labelled circuit diagram explain full wave rectification using junction diode.
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Q. 21. Two capacitors C₁ = 3µF and C₂ = 6µF arranged in series are connected in parallel with a third capacitor C₃= 4µF. The arrangement is connected to a 6,0 V battery. Calculate the total energy stored in the capacitors.
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Q. 22. A series battery of 10 lead accumulators each of e.m.f. 2V and internal resistance 0.25 Ω. is charged by a 220 V D.C. mains. To limit the charging current a resistance of 475 Ω is used in series in the charging circuit. What is (a) the power supplied by the mains and (b) power dissipated as heat. Account for the difference of power in (a) and (b).
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Q. 23. Describe an experiment to demonstrate transverse wave nature of light.
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Q. 24. Draw the curve showing variations in binding energy per nucleon with mass number. Explain the release of energy in the process of nuclear fission and fusion on the basis of this curve.
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Q. 25. With a proper circuit diagram, show the biasing of a NPN transistor. Explain the movement of charge carries through different parts of the transistor. Hence show that l_e = I_b + I_c.
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Q. 26. A galvanometer coil has a resistance of 30Ω. and the meter shows full scale deflection for a current of 2.0 mA. Calculate the resistance required to convert it into an ammeter of range 0 to 1 A. Also calculate the net resistance of the ammeter.
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Q. 27. A thick straight copper wire carrying a current of 10 A is bent into a semicircular arc of radius 7.0 cm as shown in figure (a). State the direction and calculate the magnitude of the magnetic field at the centre of the arc. How would your answer change if the same wire is bent into a semicircular arc of the same radius but in opposite way as shown in figure (b).
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Q. 28. Define the terms electric dipole and dipole moment. Derive an expression for the electric field intensity at a point on equitorial line of a dipole.

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With the help of a labelled diagram, explain the working of a van de Graaff generator. Mention its use.
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Q. 29. What is photoelectric effect? Give any two practical applica¬tions of this effect. Write Einstein’s photoelectric equation and use it to explain the:
(i) independence of maximum energy of the emitted photoelectron from the intensity of incident light.
(ii) existence of a threshold frequency for a given photosensitive surface.
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Q. 30. An LC circuit contains a 20 mH inductor and a 30 µF capacitor with an initial charge of 10 mC. The resistance of the circuit is negligible. Assume the instant the circuit is closed to be t = 0.
(a) What is the total energy stored initially?
(b) What is the frequency and time period of LC oscillations?
© At what time is the energy stored
(i) completely electrical (i.e., stored in the capacitor) ?
(ii) completely magnetic (i.e., stored in the inductor) ?
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Q. 1. Define atomic mass unit (a.m.w.) write the energy equivalent of atomic mass unit in MeV.
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Q. 2. Why does the electrical field inside a dielectric decrease when it is placed in an external electric field?
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Q. 3. State any rule which relates the direction of electric current and the direction of the accompanying magnetic field.
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Q. 4. What is the phase difference between the voltage drop across L and C in a series LCR circuit connected to an a.c, source?
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Q. 5. Arrange the following radiations in the descending order of their wavelengths. Radio waves, X-rays, UV rays, Red light.
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Q. 6. A transistor is being used as a common emitter amplifier. What is the value of phase difference, if any, between the collector-emitter voltage and the input signal?
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Q. 7. Two wires A and B of the same material and having same length have their crosssectional areas in the ratio 1: 4. What would be the ratio of heat produced hi these wires when same voltage is applied across each?
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Q. 8. Why does the conductivity of a semiconductor increase with rise in temperature?
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Q. 9. Define the term critical angle for a given pair of media. Establish its relationship with their refractive index.
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Q. 10. Observations on a given device yielded-the following current-voltage data.
Current Voltage
(Ampere) (Volt)
1.0 19.7
2.0 39.4
3.0 59.1

Current (Ampere) Voltage
4.0
5.0 (Volt)
78.8
98.5
Draw V-I graph using the above data
What conclusion can you draw from the graph with regard to ohmic or non-ohmic nature of device?
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Q. 11. Suppose you have two bars of identical dimensions—one made of paramagnetic substance and the other of dia-magnetic substance. If you place these bars along a uniform magnetic field, show diagramatically, what modifications in the field pattern would take place.
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Q. 12. What are thermal neutrons? Why are neutrons considered as ideal particles for nuclear fission?
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Q. 13. Calculate the equivalent capacitance between the points A and B in the following combination.
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Q. 14. A wire of resistance 4R is bent in the form of a circle. What is the effective resistance between the ends of diameter?
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Q. 15. A magnetised needle in a uniform magnetic Held experience a torque but no net force. However an iron nail near a bar magnet experien¬ces a force of attraction in addition to a torque. Explain.
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Q. 16. Figure below shows an inductor L and a resistor R connected in parallel to a battery through a switch. The resistance of R is the same as that of the coil that makes L. Two identical bulbs are put in each arm of the circuit
(i) which of the bulbs lights up earlier when S is closed ?
(it) will the bulbs be equally bright after some time ?
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Q. 17. A convex lens made up of a material of refractive index µ₁ is immersed in a medium of refractive index µ₂. Trace the path of a parallel beam of light passing through the lens when
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Q. 18. The wave length of the second line of the Banner series in the Hydrogen spectrum is 4861 A. Calculate the wavelength of the first line.
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Q. 19. With the help of a circuit diagram explain how can you find the internal resistance of a primary ceil? Derive the necessary formula used.
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Q. 20. Draw the logic symbol and the truth table of an OR gate. Describe its realisation with circuit diagram using semi-conductor diode.
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Q. 21. (a) State and explain Huygen’s principle.
(b) Name the type of wave front that corresponds to a beam of light
(i) coming from a very far-off source
(ii) diverging radially from a point source.
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Q. 22. How will you determine the temperature of the sun? Derive the necessary formula used.
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Q. 23. A student has two wires of iron and copper of equal length and diameter. He first joins the two wires in series and passes electric current through the combination which increases gradually. After that he joins the two wires in parallel and repeats the process of passing current. Which wire will glow first in each case and why?
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Q. 24. A sunshine recorder globe of 30 cm diameter is made of glass of refractive index µ=1.5. A ray enters the globe parallel to the axis. Find the position from the centre of the sphere where the ray crosses the axis.
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Q.25. Differentiate between n-type and p-type semiconductors on the basis of energy band diagrams. Explain the process of conduction in both type of materials.
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Q. 26. The frequency of a cyclotron oscillator is 10⁷ Hz. What should be the operating magnetic field for accelerating protons? If the radius of the dees of the cyclotron is 6 x 10^-1 m. Calculate the energy of the proton beam produced by it in MeV. (e = 1.6 x 10^-19 C, mp = 1.67 x 10^-27 kg;
1 MeV = 1.602 X I0^-13 joule.)
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Q. 27. A narrow monochromatic beam of light of intensity / is incident on a glass plate. Another identical glass plate is kept close to the first one and parallel to it. Each plate reflects 25 % of the incident tight and transmits the remaining. Calculate the ratio of minimum and maximum intensity hi the interference pattern formed by two beam obtained after reflection from each plate.
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Q. 28. With the help of a labelled diagram explain the principle, construction and working of an a.c. generator.

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With the help of a labelled diagram explain the principle, construction and working of a step up transformer. Why is the core laminated?
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Q. 29. A glass rod rubbed with silk is brought close to two uncharged spheres in contact with each other inducing charge on them as shown in figure. Show with diagrams in each case what happens when
(i) The spheres are slightly separated?
(ii) The glass rod is subsequently removed?
(iii) The spheres are separated far apart?
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Q. 30. A photon of wavelength 3310 A falls on a photo cathode and an electron of energy 3 X 10^-19 joule is ejected. If the wavelength of the incidence photon is changed to 5000 A, the energy of the ejected electron is 9.71 x 10^-20 joule. Calculate the value of Plank’s constant and threshold wavelength of the photon.
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Q 1, Is electric flux a scalar or vector quantity? Write its SI unit.
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Q. 2. Name the wave phenomenon which is exhibited by light waves but not by the sound waves.
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Q. 3. Two star A and B have magnitudes of - 2 and 3 respectively, which of the two is brighter and by how much?
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Q. 4. Will the drift speed of free electrons in a metallic conductor increase or decrease with the increase in its temperature?
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Q. 5. A magnetic needle, free to rotate in a vertical plane, orients itself with its axis vertical at a certain place on the earth. What are the values of?
(a) horizontal component of earth’s magnetic field.
(b) angle of dip at this place.
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Q. 7. A steady current flows in a metallic conductor of non-uniform cross-section. Which of the following quantities is are constant along the conductor: current, current density, drift speed,
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Q. 8. The variation of p, d. with length in case of two potentiometers A and B as given below, which of the two is more sensitive?

Q. 9. State Kirchhoffs laws for an electric network.
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Q. 10. What is meant by ‘interference of light’? Write any two conditions necessary for obtaining well-defined and sustained interference pattern of light.
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Q. 11. Define the angular dispersion. Draw the path of a ray of white light passing through a prism and mark angular dispersion on it.
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Q. 12. The radius of curvature of each surface of a convex lens of refractive index 1.5 is 40 cm. Calculate its power.
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Q. 13. Obtain the relation between the frequency of revolution of a planet and its orbital radius.
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Q. 14. A sphere Si, of radius rt encloses a total charge Q. If there is another concentric sphere S₂ of radius r₂ (r₂ >r₁) and there is no additional charges between S₁ and S₂, find the ratio of electric flux through Si and S₂.
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Q. 15. A simple voltaic cell has an e.m.f. of 10 V. Is there a net field inside the cell when (i) circuit is open (ii) circuit is closed and a steady current is drawn from it. Explain your answers in each case.
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Q. 16. Suppose a helical spring is suspended from the roof of a room and a very small weight attached to its lower end. What will happen to the spring when a current is passed through it. Give reasons to support your answer.
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Q. 17. A charged oil drop falls under gravity with a terminal speed v. The drop is held stationary by applying suitable electric field in a Millikans set up and is found to carry 2 excess electron. Suddenly the drop is observed to move upwards with the same velocity. Why does the drop move upward. Write relevant mathematical equations in support of your answer.
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Q. 18. If the emitter and the base of a npn transistor have the same doping concentration. Explain how will the collector and base currents be affected?
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Q. 19. What is See beck effect? Draw a curve to show the variation of thermo e.m.f. with the gradual increase in the temperature of hot junction. Mark the neutral temperature and temperature of inversion of the thermocouple on the curve.
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Q. 20. Draw the logic symbol and write the truth table of AND gate. With the help of a circuit diagram describe the realisation of AND gate using semiconductor diodes.
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Q. 21. What is meant by the current sensitivity of a moving coil galvanometer? On what factors does it depend? In an exercise to increase current sensitivity of a galvanometer by 25% its resistance is also increased 1.5 times. How will the voltage sensitivity of the galvanometer be effected?
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Q. 22. An electron beam of initial energy 18 keV moving horizontally is subjected to a horizontal magnetic field of 0.4 G normal to the initial direction. Calculate the vertical deflection of the beam over a distance of 30 cm.
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Q. 23. When 100 V DC is applied across an inductor, a current of 1A flows through it. If the same inductor is connected to a 100 V AC source the current reduces to 0.5 A. Why is the current reduced in the later case? Calculate the value of reactance of the inductor.
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Q. 24. Monochromatic light of wavelength 589 nm is incident from air on water surface. What are the values of wavelength, frequency and speed of (a) reflected light (b) refracted light. Refractive index of water is 1.33.
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Q. 25. A radioactive isotope decays in the following sequence:
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If the mass number and atomic number of A2 are 176 and 71 respec¬tively, find the mass number and atomic number of Ai and A. Which of the three elements are isobars?
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Q. 26. With the help of a circuit diagram explain the use of npn transistor as an amplifier in common emitter configuration. What is the phase relation between collector and base voltage?
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Q. 27. Using the data given below, state which two of the given lenses will you prefer to construct a best possible (0 telescope (ii) microscope. Also indicate which of the selected lenses is to be used, as an objective and eye piece in each case.
Lenses Power (P) Aperture (A)
L1 6D lcm
L2 3D 8 cm
L3 10D 1 cm
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Q. 28. State Bohr’s postulate of atomic model. Derive an expression for the energy of an electron.
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Q. 29. A parallel plate capacitor with air between its plate having plate area of 6 x 10^{- 3} m² and separation between them 3 mm is connected to a 100 V supply. Calculate charge on each plate of the capacitor. Explain what would happen when a 3 mm thick mica sheet (dielectric constant, K = 6) is inserted between the plates.
(i) While the voltage supply remains connected. :
(ii) After the supply is disconnected.

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Derive an expression for the energy stored in a capacitor of capacitance C. When it is charged by connecting it to a battery of pd V. Now if the capacitor is disconnected from the battery. What will be the energy stored in the capacitor? When (i) separation between the plates is doubled and (ii) an uncharged identical capacitor is connected across it.
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Q. 30. A small town with a demand of 880 kW of electric power at 220 V is situated 15 km away from an electric plant generating power at 440 V.
The resistance of the cable carrying power is 15Ω. The town gets power through a 4400 - 220 V step down transformer at a sub-station in the town.
(i) Calculate the line power loss in the form of heat.
(ii) How much power must the plant supply, assuming there is a negligible power loss due to leakage?
(iii) Calculate the voltage drop in the line.
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Q. I. What is the maximum value of the angle of dip?
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Q. 2. What is the resistance an ideal voltmeter?
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Q. 3. The refractive index of glass is 3 / 2 and that of water is 4 / 3. What is the refractive index of glass with respect to water?
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Q. 4. Half-life of a certain radioactive material against a-decay is 138 days. After what lapse of time the undecayed fraction of the material will be 6.25%?
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Q. 5. The angle of maximum elongation for the planet Venus is approximately 47°. Calculate in astronomical units and metre the distance of Venus from earth.
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Q. 6. What is shape of the trajectory of a-particle scattered in Rutherford’s experiment?
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Q. 7. The wavelength of electromagnetic radiation is doubled. What will happen to the energy of photons?
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Q. 8. State two reasons why electrolytes have lower electrical conductivity than metallic conductors in general.
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Q. 9. If the Young’s double slit experiment is immersed in water, how will the fringe width change?
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Q. 10. What are the dimensions of resistance?
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Q. 11. Draw a graph showing the dependence of intensity of transmitted light on the angle between polarizer and analyzer.
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Q. 12. A short bar magnet of magnetic moment 0.9 JT^-1 (joule per tesla) placed with its axis at 45° with a uniform external magnetic field experiences a torque of magnitude 0.063 J. Find the strength of the mag¬netic field.
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Q. 13. Define resistivity of a conductor. How does it vary with temperature?
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Q. 14. A 10 Ω thick wire is stretched so that its length becomes three times. Assuming that there is no change in its density on stretching. Calculate the resistance of the new wire.
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Q. 15. Is photoelectric emission possible at all frequencies? Give reasons for your answer.
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Q. 16. Calculate the capacity of an isolated charged metal sphere.
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Q. 17. What is a comet? Why is the tail of a comet always pointed away from the sun?
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Q. 18. What is the basic difference between a magnetic dipole and an electric dipole?
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Q. 19. Explain why the sky appears blue?
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Q. 20. Give one use of each of the following:
(i) Microwaves,
(ii) infra-red waves, (iii) ultra-violet radiation, and
(iv) Gamma rays.
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Q. 21. The focal length of the eye piece of a certain microscope is 2.5 cm. The focal length of the objective is 16 mm. The distance between the objective and the eye piece is 22.1 cm. What is the linear magnification if the final image from the eye piece is formed at infinity?
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Q. 22. After charging a capacitor, the battery is disconnected. A dielectric slab is slipped between the two plates of the capacitor. What changes, in charge capacitances, potential differences and energy stored will be observed?
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Q. 23. Show that radioactive decay is governed by the law N (t) = N (o) e ^{-λ t} where N (o) is the number of radioactive nuclei at t = 0 and λ is a constant.
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Q. 24. Find an expression for the magnitude of the force on a current carrying conductor placed in a uniform magnetic field starting from the Lorentz’s force on a moving charge. On the basis of this expression define the direction of magnetic field.
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Q. 25. Find the electric field and the potential of the electric field due to two concentric spherical shells of radii R1 and R2 for a point whose distance from the common centre is r where (a) r>R² (b)r< R^1.
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Q. 26. A capacitor C is connected in series with a resistance R. A charge qo is given to the condenser. Show that the charge decreases exponentially with time constant RC.
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Q. 27. What do you mean by mutual inductance? What is its unit?
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Q. 28. Draw the intensity profile of interference fringes due to Young double slits of equal width.
In a Young’s double slit experiment screen is kept 100 cm from the slits. The third bright fringe is at a distance of 2.945 mm from the first dark fringe. What is the wavelength of the light used 3? The distance between the slits is 0.5 mm.
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Q. 29. Draw the circuit diagram of a voltage regulator circuit using a zener diode and explain its working.
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Q. 30. A sinusoidal emf is applied to a circuit containing an inductor only. Show that current lags behind the voltage by Π/2.
A coil has an inductance of 1 henry (a) at what frequency will it have a reactance of 3142 ohms? (b) What should be the capacity of a capacitor which has the same reactance at that frequency?

OR

What is meant by the root mean square or effective value of alternating current? Derive a relation between it and its peak value.
The electric mains in the house are marked 220 V, 50 Hz. Write down the equation for instantaneous voltage.
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Q. 1. The refractive index of the material of an equi-double convex lens is 1.5. Write the relation between the focal length and the radius of curvature?
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Q. 2. What is the wavelength range of microwaves?
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Q. 3. Indicate the position of a magnetic diopole held in a magnetic field, where its potential energy is minimum.
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Q. 4. Write the value of the critical angle for a material of refractive index V2.
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Q.5. If the frequency of tight falling on a metal surface is doubled, will the kinetic energy of emitted photoelectrons doubled?
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Q. 6. How is a Gauss related to Weber/ (metre) ²?
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Q. 7. Why sky waves are not used in the transmission of television signals?
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Q. 8. What factors make a fusion reactions difficult to achieve?
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Q. 9. A a.c. voltage E = E_o sin cor is applied across an inductance L. Obtain an expression for the current/.
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Q. 10. Draw a labelled energy level diagram for the decay of ⁶⁰₂₇ Co mucleus.
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Q. 11. A charged particle is moving on a circular path of radius R in a uniform magnetic field under the Lorentz’s force F. How much work is done by the force in one round? Is the momentum of the particle changing?
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Q. 12. What is the effect of increasing the diameter of the objective of a telescope on its (i) magnifying power and (ii) resolving power?
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Q.13. What are magnetic lines of force? Roughly trace the magnetic field lines for a bar magnet.
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Q. 14. Define Coulomb. Calculate the charge carried by 12.5 X 10⁸ electrons.
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Q. 15. State any two conditions under which light from two sources can interfere.
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Q. 16. (i) Define the term electrolysis.
(ii) Give two factors which are responsible for lower electrical conductivity of electrolytes than metals at room temperature.
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Q. 17. Light of wavelength 5500 A falls on a slit of width 0.13 cm. at normal incidence. Calculate the width of the central maximum on a screen kept 5 m away from the slit.
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Q. 18. State Ohms’ law. On what factors the resistance of a conductor depend?
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Q. 19. Obtain Bohr’s quantization condition of angular momentum on the basis of the wave picture of electron.
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Q. 20. State the magnetic properties of steel and soft iron.
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Q. 21. State tangent law. How will the reduction factor of a tangent galvanometer change when the number of turns of its coil is doubled?
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Q. 22. Prove by reasoning (without performing any calculations) that the magnetic field B on the axis at an end face of a very long solenoid is half the value in the middle of the solenoid.
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Q. 23. Define the atomic mass unit. Express its value in electron volt.
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Q. 24. In Fig. the rectangular loop of wire is being pulled to the right. What is the direction of the induced current in the loop?
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Q. 25. The energy required to ionize a hydrogen atom is 13.6 eV. It is to be ionized by the inelastic collision of (i) an electron, (ii) a hydrogen ion, (iii) a helium ion. Which of these particles must have the higher initial kinetic energy for ionization?
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Q. 26. Show that an electron of mass m entering uniform magnetic field B with a velocity v moves in a circular path.
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Q. 27. Define electric potential in an electrostatic field and express it as the line integral of the electrostatic field intensity.
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Q. 28. (a) Two conductors of capacitance C₁ and C₂ are charged to potential V₁ and V₂. They are then connected together. Calculate the common pctential and also the charges on each after connecting.

(b) A capacitor of capacitance 1.77 x 10^-10 farad has a p.d. of 3000 V. Whena 0.01 m thick sheet of dielectric material is put between the plates, the p.d. reduces to 10O0 V. Find the (i) Charge on each plate, (ii) Dielectric constant of the sheet, (iii) Capacitance of capacitor after putting the sheet, (iv) permittivity of the dielectric medium.
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Q. 29. Explain the term ‘chain reaction’. What are the functions of moderator and control rods in a nuclear reactor?
^OR

A stream of neutrons have a kinetic energy 0.0327 eV. How many half lives are spent by the neutron in a distance of 10 km ?
(Given half life of neutron equal to 700 seconds; mass of the neutron = 1.675 x 10^-27 kg).
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Q. 30. When a metal surface is irradiated with light of wavelength 4950 A, a photocurrent appears which vanishes at a retarding potential of 0.6 volt. When a different source is used, it is found that the retarding potential is now 1.1 volt. Calculate the work function of the metal surface and the wavelength of the second source.
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Q. 1. What is the approximate wavelength range for the visible spectrum?
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Q. 2. Why copper wire is not used in potentiometer?
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Q. 3. When the length of a microscope tube is increased how is its magnifying power affected?
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Q. 4. The curves show voltage current relationship for two photo cathodes illuminated by a single source. In what way the cathodes dif¬fer?
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Q. 5. A point charge is rotated in a circle of radius r around a charge q. What will be net work done?
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Q. 6. A 900 pF capacitor is charged by a 100 V battery. How much electrostatic energy is stored by the capacitor? .
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Q. 7. What is the direction of current at the cold junction of a copper-bismuth thermocouple?
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Q. 8. How do comets form tails?
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Q. 9. What are (i) terrestrial planets and (ii) jovial planets? Give one example of each.
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Q. 10. Suppose that the potential energy between electron and proton in hydrogen atom at a distance r is given by U = -ke² /3r³.
(i) What is the force between them?
(ii) What is the radius of such an orbit?
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Q. 11. What is an electromagnetic wave? How an electromagnetic wave is possible in space?
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Q. 12. Calculate the frequency associated with a photon of energy 3.3x10^-20 J. (h = 6.6x10^-34 Js).
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Q. 13. Neutrons produced in fission can be slowed down even by using ordinary water. Then, why is heavy water used for this purpose?
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Q. 14. Calculate the luminous intensity of 200 W tungsten lamp whose efficiency is 18 Im/W. What are the assumptions?
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Q. 15. An electric dipole free to move is placed in a uniform electric field. Explain along with diagram its motion when it is placed (a) parallel to the field (b) perpendicular to the field.
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Q. 16. A capacitor is joined to a cell, a resistance R, an ammeter and a key when the key is pressed write the expression for the current in terms of resistance R capacitance C and e.m.f. e.
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Q. 17. Show, by drawing ray diagrams, how a totally reflecting glass prism can be used to deviate a ray of light through (i) 90° (ii) 180°.
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Q. 18. Give a diagram from which it is clear that “taller the antenna, longer the coverage of the television broadcast".
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Q. 19. State laws of photoelectric effect
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Q. 20. In J J. Thomson’s method, prove that the specific charge of an electron is given by the expression 1/r E/B² where r is the radius of the circular path produced by electron in the region of magnetic field B and E the electric field applied.
(i) Give Huygens ‘Principle of secondary wavelets, (ii) Show graphical¬ly the intensity distribution in a single slit diffraction pattern.
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Q. 21. The critical angle for total internal reflection for saphire surrounded by air is 34.4°. Calculate the polarising angle for saphire if the light is incident from air.
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Q. 22. Define capacitance. Derive an expression for the capacitance of a parallel plate capacitor with vacuum.
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Q. 23. A circular conducting wire loop of radius r, with a current i is placed in a magnetic field perpendicular to its plane. Find the force on a small part dl of the conducting wire and the force of compression in the wire. When the magnetic field is switched off what happens to the radius of the loop?
Image
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Q. 24. (i) What is electrolysis? (ii) How long will it take to deposit electrolytically 10.79 g of silver on the cathode of a silver voltmeter by a current of 25 A? (ece of silver = 0.001118 g/C).
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Q. 25. Explain how the masses of two stars belonging to a binary system can be determined?
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Q. 26. Show that the angle of minimum deviation produced by a thin prism is reduced to one-fourth (with respect to air) when it is immersed hi water. Given _en_g = 3/2 and _en_w = 4/3.
Answer

Q. 27. (a) Show that the contact potential difference between two dissimilar metals is given by
φ = W₁-W₂ / e
where W₁ and W₂ are the work functions of the metals.
(b) The e.m.f of a zinc carbon cell is 1.5 volt, how much energy will a system have on dissolution of one zinc ion in a voltameter?
Answer

Q. 28. State Lenz’s law. Show how Lenz’s law follows from the principle of conservation of energy?
Answer

Q. 29. State and explain Faraday’s laws of electrolysis. Define electrochemical equivalent.

OR
Doppler effect can help to decide whether a star is approaching or receding from the earth. Explain how?
Answer

Q. 30. Describe Millikan’s oil drop experiment for determination of charge on an electron.

OR

Drawa ray diagram to show the formation of image of an object placed between the pole and centre of curvature of a concave mirror. Derive the formula connecting object distance (u), image distance (v) and focal length (f) for this particular case for the given concave mirror. State clearly the assumption and sign convention used.
Answer

Q. 1. State two factors on which the sensitivity of a moving coil galvanometer depends.
Answer

Q. 2. What is the physical quantity measured by kilogram metre per cubic second per ampere?
Answer

Q.3. A glass rod whenrubbed with silk acquires a charge + 1.6 X 10^-12 C. What is the charge on the silk?
Answer

Q.4. The wavelength of an electro magnetic wave is 10 mm, to what part of the spectrum it belongs?
Answer

Q. 5. In an a.c. circuit why there is no power consumption in an inductor?
Answer

Q. 6. Name a device for producing polarised light
Answer

Q. 7. A conducting loop of radius r carries a constant current i and is placed in a uniform magnetic Held B such that B is perpendicular to the loop. What is the magnetic force acting on the loop?
Answer

Q. 8. Give the main reason for the necessity of ozone layer for the survival of life on the earth.
Answer

Q. 9. How can paramagnetic and diamagnetic material rods be distinguished in a magnetic field?
Answer

Q. 10. Give any two differences between Asteroids and Meteoroids.
Answer

Q. 11. What percentage of a given mass of a radioactive substance will be left undecayed after five half-life periods?
Answer

Q. 12. The work function of aluminium is 4.2 eV. If two photons each of energy 2.3 eV strike together a surface electron of aluminium, what is the energy of the photons emitted?
Answer

Q. 13. Show graphically the variation of charge q with time t, when a condenser is charged. Write the equation for the graph.
Answer

Q. 14. An electron is projected with a velocity of 10⁵ ms^-1 at right angles to a magnetic field of 0.19G. Calculate the radius of circle described
by electron. (Given e 1.6 x 10 ^-19 Coulomb, m = 9.1 x 10^-31 kg).
Answer

Q. 15. A concave spherical mirror of focal length 30 cm is to be used to form a real image thrice the size of the object. What object distance should be used?
Answer

Q. 16. The mass of a proton is much larger than the electron. An electron and proton of equal kinetic energies, enter perpendicularly a uniform electric field. Which of the paths is more curved?
Answer

Q. 17. Why do we use short waves for long distance radio broadcast?
Answer

Q. 18. Two wires of the same material having lengths in the ratio of 1: 2 and diameteres in the ratio 2: 3 are connected in series with an accumulator. Compute the ratio of the p.d. across the two wires.
Answer

Q. 19. If different isotopes of the same element have the same chemical behaviour how can they be separated?
Answer

Q. 20. What is an electromagnet? Give two uses of an electromagnet.
Answer

Q. 21. What is half-life? A radioactive sample has 8.0 x 10-18 active nuclei when we start counting time. How many of these nuclei will still be in the same state after two half-lives?
Answer

Q. 22. Deduce the expression for fringe width in Young’s double slit experiment.
Answer

Q. 23. An electron is projected towards the positive plate of a parallel plate capacitor charged to a potential difference V. A magnetic field B also exists between the plates. What must be the minimum separation d between the plates so that the electron does not fail to strike the positive plate?
Answer

Q. 24. In a magnet, neutral points are found along the axis of the magnet In what direction the magnet is placed? Write the expression connecting magnetic moment m of the magnet and the earth’s horizontal component.
Answer

Q. 25. Sun’s angular diameter is about 0.5°. Its distance from earth is about 1.5 x 10⁸ km. What is its diameter?
Answer

Q. 26. Define contact potential. Give its relation to the work function.
Answer

Q. 27. If a copper wire is stretched to make 0.1 % longer, how will its resistance change?
Answer

Q. 28. is desired to operate a 100 W, 120 V lamp at its current on 240 V—50 Hz supply. Give details how it could be done using: (i) a resistor (II) a capacitor (ii) a coil of 10 Ω, resistance and inductance.
Answer

Q. 29. What is the resolving power of a lens? Explain Rayleigh’s Criterion. A telescope is used to observe two distant points 1 m part. The wavelength of light may be taken as 5000 A. The objective of the telescope is covered with a slit of 1 mm width. At what maximum distance the two sources can be distinguished?
What is the effect of decreasing the width of slit?
Answer

Q. 30. How (i) AND gate is realised using NAND gate (ii) OR gate is realised using NAND gate (iii) NOT gate is realised using NAND gate.
Answer

Q. 1. How does the atmospheric temperature change with altitude in the range 0-50 km?
Answer

Q. 2. A wire of resistance 16 ohm is melted and drawn into a wire of half its original length. What is the resistance of the new wire?
Answer

Q. 3. A dip needle lies in a plane perpendicular to the magnetic meridian, in what direction will it point?
Answer

Q. 4. Give one practical application of thermoelectricity.
Answer

Q. 5. The curves show voltage-current relationship for a photo—cathode illuminated by different sources of light. In what way the sources differ? In what way are they similar?
Image
Answer

Q. 6. The deflection of a galvanometer falls from 25 to 10 divisions when a shunt of 5 ii is connected across it. What is the resistance of the galvanometer?
Answer

Q. 7. For the same angle of incidence the angles of refraction in three different media A, B and C are 15°, 25° and 35° respectively. In which medium is the velocity of light maximum?
Answer

Q. 8. Electric charges q, q and - 2q are placed at the corners of an equilateral triangle of side /. What is the magnitude of the dipole moment of the system?
Answer

Q. 9. When a battery of e.m.f. E and internal resistance r is connected to a resistance R, a current / flows through it. Derive a relation between E, I, r and R.
Answer

Q. 10. Does an iron bar magnet retain its magnetism when melted? Give reason for your answer.
Answer

Q. 11. A current of 5.0 A flows through an electric press of resistance 44 O. Calculate the energy consumed by the press in 5 minutes.
Answer

Q. 12. A compound microscope has a magnification of 36. The focal length of its eye piece is 5 cm. Assuming the final image to be formed at the least distance of distinct vision (25 cm.), calculate the magnification produced by the objective.
Answer

Q. 13. The Fig. shows an achromatic telescope objective made of two lenses, one of crown and other of flint glass, (i) Which of the two lenses has a larger focal length and why ?
(ii) The material of which lens has a larger dispersive power?
(m) Which of the lenses is made of crown glass and which one of flint glass?
Image
Answer

Q. 14. Derive an expression for the electric field intensity at a distance V from a point charge ‘q’.
Answer

Q. 15. What is magnifying power for a visual optical instrument? Define it for a microscope.
Answer

Q. 16. An electron beam is deflected in a given field. How will you detect whether the given field is a uniform magnetic field or a uniform electric field?
Answer

Q. 17. A bridge circuit is shown in the Fig. It is to act as a full wave rectifier (i) where must the a.c. input be connected ? (ii) where will the d.c. output appear ? Indicate that current through the diodes after completing the diagram.
Image
Answer

Q. 18. Calculate the force per unit length on a long straight wire carrying of 2 A due to a parallel wire carrying 6 A current. Distance between the wires is equal to 3 cm.
Answer

Q. 19. Explain how you will convert a galvanometer into an ammeter of a given range.
Answer

Q. 20. A circuit consisting of a 12 V battery, a 2.7Ω resistance and a switch is opened. The internal resistance of the battery is, 0.3 Ω. What is the voltmeter reading (i) across the battery (ii) across the resistance (iii) across the switch? What are these values when the Switch is closed?
Answer

Q. 21. The total energy of H atom when the electron is in the second quantum state is E₂. What is the total energy of He+ ion in the third quantum ‘ state?
Answer

Q. 22. A ray of light falls normally on the face of an isosceles prism u as shown. What is the minimum value of refractive index of the prism?
Image
Answer

Q. 23. The current gain of a transistor in common-base arrangement is 0.98. Find the change in collector-current corresponding to a charge of 5.0 mA in emitter-current. Find the change in the base current.
Answer

Q. 24. A series LCR circuit with L = 5.0 H, C = 80 μF and R = 40Ώ is connected to a variable frequency source of 230 V.
(0 Determine the resonance frequency of the circuit.
(a) Obtain the impedance of the circuit and the amplitude of the current at resonance.
Answer

Q. 25. An aeroplane having a wings span of 50 m is flying horizontally with a speed of 100 ms^-1 at a place with an angle of dip 30°. (Earth’s total field is 4.0 x 10^-5 Wb/m²). Calculate the induced potential difference between the edges of the wings.
Answer

Q. 26. Show that the maximum magnifying power M of a simple microscope is given by:
M = 1 + D/f, where f = focal length and D = distance of distinct vision.
Answer

Q. 27. Describe how the distance and size of a planet can be measured from the earth?
Answer

Q. 28. Explain the phenomenon of glow discharge m a cathode ray tube. How are electrons knocked on of the cathode?

OR

A coil of inductance 0.2 H and resistance 1.0 Ω is connected to a 20 V source (a) What is the rate of growth of current at the instant the coil is connected to the source (b) What is the current when the rate of growth is 100 A/s?
Answer

Q. 1. Mention two defects of a simple cell.
Answer

Q. 2. When are the voltage and current in a LCR series A.C. circuit in phase?
Answer

Q. 3. Why cannot two magnetic lines of forces due to a bar magnet cross each other? .
Answer

Q. 4. The magnetic flux threading a coil changes from 12 X 10^-3 Wb to 7 X 10^-3 Wb in 0.01 s. Calculate the induced e.m.f.
Answer

Q. 5. What are comets composed of?
Answer

Q. 6. Suppose planet goes around the sun twice as fast as earth what will be its orbit size as compared to that of the earth?
Answer

Q. 7. What oscillates in electromagnetic waves? Are these waves transverse or longitudinal 7
Answer

Q. 8. Write the relationship between amplitudes of electric and mag¬netic fields in free space for an electromagnetic wave,
Answer

Q. 9. Explain how the conductivity of an electrolyte increases with the concentration of the ions and their mobility.
Answer

Q. 10. Define elliptically polarised light.
Answer

Q. 11. What should be the minimum energy of electron exciting the hydrogen atom so that three spectral lines are excited?
Answer

Q. 12. How can you produce dispersion without deviation?
Answer

Q. 13. Calculate the Binding energy per nucleon of ⁴⁰₂₀Ca nucleus, (mass of ⁴⁰₂₀Ca = 39.96259 amu, mass of neutron 1.00866 amu, mass of proton 1.00782 amu).
Answer

Q. 14. When an A.C. circuit with L, C and R in series is brought into resonance, the current has large value, why? If the capacitance of C is increased, will the current increase or decrease? Explain with suitable relation.
Answer

Q. 15. Why it is necessary to use small wavelengths of light to increase the resolving power of a microscope?
Answer

Q. 16. The value of solar constant at the surface of the earth is 1400 Wm^-2. Compute its value at Jupiter which is 5.2 AU from the sun.
Answer

Q. 17. Prove that the induced charge does not depend upon the rate of change of flux.
Answer

Q. 18. A nucleus _nX emits one α-particle and one β-particle. What are the mass number and the atomic number of the product nucleus?
Answer

Q. 19. An oil drop carries six electronic charge has a mass of 1.6 x 10 gram and falls with a terminal velocity in air. What magnitude of vertical electric field is required to make the drop move upwards with the same speed as it was formally moving downward?
Answer

Q. 20. What is the principle of vibration magnetometer?
Answer

Q. 21. Distinguish between intrinsic and extrinsic semiconductors.
Answer

Q. 22. Show, by drawing ray diagrams, how a totally reflecting glass prism can be used to deviate a ray of light through (0 90 ° (ii) 180°.
Answer

Q. 23. Calculate the magnetic force acting on a closed loop carrying a current placed in a uniform magnetic field B?
Answer

Q. 24. If the distance of any one of the planets from the sun is known, how can the distance of any other planet be calculated?
Answer

Q. 25. Show that the trajectory of an electron entering perpendicularly in a uniform electric field is a parabola.
Answer

Q. 26. Obtain an expression for the force between infinitely long straight line conductors parallel to each other. Hence define one ampere.
Answer

Q. 27. Derive a formula for combined focal length of two thin convex lenses in contact.
Answer

Q. 28. What are Eddy currents? How are these produced? Give one application.

OR

Explain with necessary theory how will you compare the intensity of illumination of two sources of light using B usen’s grease spot photometer.
Answer

Q- 29. (a) What is the importance of power factor?
(b) An electric bulb of 200 W, 240 V is joined in series with an inductance 0.15 H and * capacitor at 220 V. What is the capacitance if the active power in the circuit is half of the total power? What is the current in the circuit?
Answer

Q. 30. A sinusoidal emf is applied to a circuit containing a capacitor only. Show that current leads the voltage by π /2.

Find the maximum value of current when an inductance of one henry is connected to an a.c. source of 200 volts, 50 Hz.

OR

Derive an expression for the instantaneous value of the induced emf in a coil when it is rotated in a uniform magnetic field at a uniform angular velocity. How does the emf vary when the coil rotates through an angle of 2 π?
What is the instantaneous value of induced emf when the plane of the coil makes an angle of 60° with the magnetic lines?
Answer

Q. I. State one basic property of electric charge.
Answer

Q. 2. How much current be passed through a long wire so that it produces a magnetic field of 1 testa at a distance of 10 cm from it?
Answer

Q. 3. What types of charge carriers are there in a p-type semiconductor?
Answer

Q. 4. What is the dynamic mass of a photon of frequency v?
Answer

Q. 5. Write two conditions for the existence of atmosphere on a planet.
Answer

Q. 6. Which type of biasing results in very high resistance of a p-n junction diode? Draw a diagram showing this bias.
Answer

Q. 7. What is the energy associated in joules with a photon of wavelength 4000 A?
Answer

Q. 8, On what factors the number of radioactive nuclei which undergo decay depend?
Answer

Q. 9. Differentiate between radiant flux and luminous flux.
Answer

Q. 10. Why is plane current loop considered a magnetic dipole?
Answer

Q. 11. A 1.5 µF capacitor has a capacitive reactance of 6Ω what is the frequency of the source? If the frequency of the source is doubled, what will be the capacitive reactance?
Answer

Q. 12. What are Fraunhofer lines? How are they produced?
Answer

Q. 13. A proton moves with a speed of 7.45 x 10⁵ ms^-1 directly towards a free proton originally at rest Find the closest distance for the two protons, (mass of proton = 1.66 x 10^-27 kg).
Answer

Q. 14. What is Green house effect for the atmosphere of the earth and what is its importance? Draw a labelled diagram in support of your answer.
Answer

Q. 15. Derive the expression for the electric potential at a distance V from a point charge ‘q’.
Answer

Q. 16. Give the name of the source and the spectral range of the following wavelength: 6000 A Å 200 m, 0.5 Å and 1200 Å.
Answer

Q. 17. Assuming the diameter of the eye pupil to be 2.0 mm, calculate die smallest angular separation at which two point objects can be distinctly seen when viewed in light of wavelength 6000 Å.
Answer

Q. 18. Explain emission of gamma rays with an example.
Answer

Q. 19. (a) How can the value of Plank’s constant be determined from the experiments of photoelectric effect?
(b) Photon is a zero-mass particle, explain briefly.
Answer

Q. 20. If photo electrons are to be emitted from a potassium surface with a speed of 6 x 10⁵ ms^-1 what frequency of radiation must be used? (Threshold frequency for potassium is 4.22 X 10¹⁴ Hz, h = 6.6 X 10^-34 Js and me = 9.1 x 10^{- 31} kg).
Answer

Q. 21. How is the depletion region formed in a p-n junction diode?
Answer

Q. 22. Derive an expression for the magnetic field on the axis of a toroidal solenoid.
Answer

Q. 23. Draw a labelled diagram of Geiger-Marsden experiment on the scattering of α-particles. How is the size of nucleus estimated in this experiment?
Answer

Q. 24. Describe how spectrometer can be used to obtain pure spectrum.
Answer

Q. 25. A magnet suspended at 30° with the magnetic meridian makes an angle of 45° with the horizontal. What is the actual value of the angle of dip?
Answer

Q. 26. Explain the phenomenon of hysterisis in ferromagnetic materials.
Answer

Q. 27. An 80 V, 800 W heater is to be operated on a 100 V, 50 Hz supply. Calculate the inductance of the choke required.
Answer

Q. 28. (a) Prove mathematically that the average value of alternating current over one complete cycle in zero.
(b) A series LCR circuit consists of a resistance of 10 Q., a capacitor of reactance 60 Q and an inductor coil. The circuit is found to resonate when put across 300 V, 100 Hz supply. Calculate
(i) the inductance of the coil
(ii) current in the circuit at resonance.
Answer

Q. 29. Derive an expression for the resistivity of a were in terms of its material parameters—number density of free electrons and collision time.

OR

You are required to determined the specific resistance of the material of a wire in the laboratory. Draw the circuit diagram. Explain the principle of experiment. Give the formula used.
Answer

Q. 30. What are secondary cells? Explain in brief the charging and discharging of a lead accumulator.
Answer