CBSE Board Class 12 Physics Sample Papers 2008

Sample Paper – 2008
Class – XII
Subject - Physics

Max Marks - 70
Min Marks - 28

Section-A

1. Why metals cannot be used as a dielectric in a capacitor?

2. A closed loop of wire is being moved so that it remains in a uniform magnetic field. What is the current induced?

3. When can a charge act as a source of electromagnetic waves? How are the directions, of the electric and magnetic field vectors, in an electromagnetic wave, related to each other and to the direction of propagation of the wave?

4. Draw a graph showing the variation of intensity of polarized light transmitted by an analyzer?

5. Two nuclei have same mass numbers in the ratio 1:8. What is the ratio of their nuclear radii?

6. What is an ideal diode? Draw the output waveform across R, for the input waveform given below:

7. What is modem?

8. If the intensity of light falling on the emitting substance of a photoelectric cell be increased then what will be the effect on (1) current flowing from the cell, (2) potential difference required to stop the current completely?

Section-B

1. Two hollow conductors are charged positively, the smaller is at 50V and the bigger is at 100V. How should they be arranged such that the charge flows from the smaller to the bigger conductor when connected by a wire?

2. Current is allowed to flow in a metallic wire at a constant potential difference. When the wire becomes hot, cold water is poured on half portion of the wire. By doing so, its other portion becomes still more hot. Explain its reason.

3. An uncharged capacitor is connected to a battery. Show that half the energy supplied by the battery is lost as heat while charging the capacitor.

4. In what respect does a wire carrying current differ from a wire, which carries no current?

5. Prove that in ac circuit containing inductance only current lags behind the voltage also draw the waveform of current and voltage.

6. Show that conduction current and the displacement current individually discontinuous but their sum is continuous?

7. Draw a graph showing the dependence of intensity of transmitted light on the angle between the polarizer and the analyzer.

8. Draw the well labeled diagram for the band theory of solids.

9. What is amplitude modulation?

10. Give three reasons that what the need for modulation is.

Section-C

1. Derive the expression for the electric field due to charged non conductiong solid sphere.

2. In the circuit shown below, each battery is 6V and has an internal resistance 0.2 ohm. What is the reading of ideal voltmeter.

3. A cell of emf 2V and internal resistance 0.1 ohm supplies a current through a coil of resistance 11.9 ohm. The current being measured by an ammeter whose resistance is 6 ohm. What reading does it give? What is the percentage difference from the actual current, when the meter is not used?

4. If there is no magnetic field of earth then would our survival be possible? Comment.

5. Derive an expression for the magnetic field on the axis of the current carrying coil.

6. State and prove prism formula.

7. Draw the well labeled diagram of the astronomical telescope at the least distance of distinct vision.

8. Draw the well labeled diagram of the davisson and germer experiment with polar graphs.

9. Why is energy distribution of β-rays are continuous?

Section-D

1. Draw the well labeled diagram of the npn-common emitter amplifier.Identify the logic gates X and Y shown in the above figure. Write down the truth table to find out the output Z.

2. Give the principle, construction, theory and working of the ac generator.

3. A spherical surface of radius of curvature R, separates a rarer and a denser medium as shown in the fig. Complete the path of the incident ray of light, showing the formation of a real image. Hence derive the relation connecting object distance u, image distance v, radius of curvature R and the refractive index n1 and n2 of the two media. Briefly explain how the focal length of a convex lens changes with the increase in wavelength of the incident light.