CBSE Physics Model Practice Question Paper- 1
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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