CBSE Physics Sample Question Paper : Set-1
Q. 1. What is the role of MnO2 in a dry cell?
Answer
Q. 2. Define a lumen.
Answer
Q. 3. A wire of resistivity p is stretched to three times its length. What will be its new resistivity?
Answer
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?
Answer
Q. 5. How does the resolving power of a telescope change when the aperture of its objective is increased?
Answer
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?
Answer
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?
Answer
Q. 8. An equiconvex lens of focal length 15 cm is cut into two equal halves as shown.
Image 
What is the focal length of each half?
Q. 9. What is meant by red shift? What does it tell about the universe?
Answer
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.
Answer
Q. 11. Write two points of difference between interference and diffraction pattern of light.
Answer
Q. 12. Calculate the refractive index of material of an equilateral prism for which the angle of minimum deviation is 60
Answer
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?
Answer
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.
Answer
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.
Answer
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.
Answer
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.
Answer
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.
Image
Answer
Q. 19. With the help of circuit diagram, explain how would you compare the e.m.fs of two primary cells using a potentiometer.
Answer
Q. 20. What is rectification? With the help of a labelled circuit diagram explain full wave rectification using junction diode.
Answer
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.
Answer
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).
Answer
Q. 23. Describe an experiment to demonstrate transverse wave nature of light.
Answer
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.
Answer
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 le = Ib + Ic.
Answer
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.
Answer
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).
Image
Answer
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.
With the help of a labelled diagram, explain the working of a van de Graaff generator. Mention its use.
Answer
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.
Answer
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) ?
Answer