: CBSE Sample Question Papers

Q. 16. Use the mirror formula to show that an object lying between the pole and focus of a concave mirror, the image formed is always virtual in nature.
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Q. 17. An alpha particle and proton are accelerated through same potential difference. Calculate the ratio of the velocities acquired by the two particles.
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Q. 18. Describe parallel method used for determination of distance of near stars.
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Q. 19. Explain the principle of tangent galvanometer. How does the reduction factor of a galvanometer changes when (i) number of turns of coil is increased, (ii) radius of the coil is decreased ?
Give reason for your answer in each case.
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Q. 20. A wire of uniform cross-section and length 1 has a resistance of 16 ohm. It is cut into four equal parts. Each part is stretched uniformly to a length 1 and all the four stretched parts are connected in parallel. Calculate the total resistance of the combination so formed. Assume that the stretching does not cause any change in density of the material of the wire.
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Q. 21. An electric heater and an electric bulb are rated 500 W, 220V ; 100W, 220V respectively. a are connected in series to 220V a.c. mains. Calculate the power consumed by (i) the heater ; and electric bulb.
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Q, 22. Why is it easier to observe diffraction of sound waves than to observe light waves ? What two changes in diffraction pattern of a single slit will you observe when monochromatic
source of light is replaced by white light ?
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Q. 23. Explain surface wave and sky wave propagation of radio waves. Winy is short wave communication over long range not possible by surface wave propagation ?
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Q. 24. Give reasons for the following observations on the surface of moon :
(i) Sun-rise and sun-set are abrupt. (ii) Sky appears dark.
(iii) Rainbow is never observed.
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Q. 25. The energy levels of an atom of element are shown in the following diagram. Which of the level transitions will result in the emission of photons of wavelength 620 nm ? Support your answer with mathematical calculations.
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Q. 26. Give logic symbol and truth table for AND gate. Explain with the help of a circuit diagram, how this gate is realised hi practice.
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Q. 27. Draw a labelled circuit diagram and explain how a NPN transistor can be used as an amplifier in common base configuration.
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Q. 28. Explain the effect of introducing a dielectric slab between the plates of a parallel plate capacitor on its capacitance. Derive an expression for its capacitance with dielectric as the medium between the plates,
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Q. 29. Distinguish between reactance and impedance. When a series combination of an inductor of inductance L, a resistor of resistance R is connected across a 12 V, 50 Hz supply, a current of 0.5 A flows through circuit. The current differs in plase from applied voltage by JE/3 radian. Calculate L and R.
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Q. 30. Explain the process of release of energy in a nuclear reactor. Draw a labelled diagramof a nuclear reactor and write down the function of each part.
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Q. 16. In diagram given below for the stationary orbits of hydrogen atom, mark (in fig a), the transitions representing the Balmer and Lyman series.
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Q. 17. The given figure shows an inductor L and resistor R connected in parallel to a battery B through a switch S. The resistance of R is the same as that of the coil that makes L. Two identical bulbs, P and Q are put in each arm of the circuit as shown. When S is closed, which of the two bulbs will light up earlier ? Justify your answer.
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Q. 18. Two point electric charges of values q and 2q are kept at a distance d apart from each other in air. A third charge Q is to be kept along the same line in such a way that the net force acting on q and 2q is zero. Calculate the position of charge Q in terms of d.
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Q, 19. Explain with the help of circuit diagram, the use of potentiometer for determination of internal resistance of a primary cell. Derive the necessary expression.
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Q. 20. Sketch the wave fronts corresponding to converging rays. Verify Snell’s law of
refraction using Huygen’s wave theory.
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Q. 21. An electric dipole is held in a uniform electric field (i) Show that no translatory force acts on it. (ii) Derive the expression for torque acting on it.
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Q. 22, Derive an expression for the width of the central maxima for diffraction of light at a single slit. How does this width change with the increase in width of the slit ?
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Q. 23. A capacitor of capacitance 100 pi¥ and a coil of resistance 5(1 Q and inductance 0.5 H are connected in series with 110V and 50 Hz source. Calculate the rms value of the current in the circuit.
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Q. 24. Draw a labelled ray diagram to show the image formation in a reflecting type telescope. Write its two advantages over refracting type telescope. On what factors does its resolving power depend ?
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Q. 26. An object is kept in front of a concave mirror of focal length 15 cm. The image formed is three times the size of the object. Calculate two possible distances of the object from the mirror.
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Q. 27. A voltmeter V of resistance 400 Q is used to measure the potential difference across a 100 Q resistor in the circuit as shown here.
(a) What will be the reading of the voltmeter ?
(b) Calculate the potential difference across 100 Q resistor before the voltmeter is connected.
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Q. 28. Derive a mathematical expression for the force per unit length acting on each of the two straight parallel metallic conductors carrying current in the same direction and kept near each other. Why do such current carrying conductors attract each other ?

OR
Derive a mathematical expression for the force acting on a current carrying straight conductor kept in a magnetic field. State the rules used to determine the direction of this force.
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Q. 29. Draw a labelled diagram of Thomson’s experimental set up to determine e/m of electrons. Explain by deriving the necessary mathematical expression, how e/m of electrons can be determined by this method.
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Q. 30. Define the term potential barrier and depletion region for a P-N junction. Explain, with the help of a circuit diagram, the use of P-N junction diode as a full wave rectifier. Draw the input and output wave-forms.
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