CBSE Physics Sample Question Paper : Set I
Q. 16. A microscope is focussed on a dot at the bottom of a 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 of x cm to bring the dot again into focus. Express refractive index of oil in terms of x and y.
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Q. 17. The energy of an electron in nth orbit is given by En = — 13-6/n2 eV. Calculate the energy required to take an electron from ground state to the second excited state.
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Q. 18. Identify the logic gates 1 and 2 in the logic circuit given below. Also write the truth table for final output for all possible combinations of the inputs A and B. 2
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Q. 19. With the help of circuit diagram, explain how would you compare the EMF’s 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 diodes.
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Q. 21. Two capacitors of capacitances C1 = 3µF and C2 = 6µF arranged in series are connected in parallel with a third capacitor C3 = 4µF. The total 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 ohm is charged by a 220V D.C. mains. To limit the charging current, a resistance of 47.5 ohm 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 in 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 the variation in binding energy per nucleons 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 carriers through different parts of this transistor. Hence show that Ie = Ib, + Ic. 3
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Q. 26. A galvanometer coil has a resistance of 30 ohm and the meter shows full scale deflection for a current of 2. 0 mA. Calculate the value of resistance required to convert it into an ammeter of range 0 to 1A. Also calculate the net resistance of the ammeter. 3
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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 arc. How would you answer change if the same wire 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 term 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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Alternative Question
With the help of labelled diagram, explain the working of a Van De Graff generator. Mention its use .
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Q. 29. What is photoelectric effect ? Give any two practical applications of this effect. Write Einstein’s photoelectric equation and use it to explain the (i) independence of maximum energy of the emitted photoelectrons from the intensity of incident light, (ii) existence of threshold frequency for a given photosensitive surface.
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Q. 30. An LC circuit contains a 20 mH inductor and a 50 µ. F 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 the LC oscillations ? © At what times 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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