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Model Sample Paper -1

Q.1. Under what conditions a concave lens can behave as a converging lens ?

Q.2. A current carrying circular loop is located in a uniform magnetic field. If the loop is free to turn. What is the orientation of stable equilibrium?

Q.3. How does the speed of light in glass change on increasing the intensity of light?

Q.4. Does the value of temperature coefficient of resistance always positive?

Q.5. On what factors does the colour of a star depend?

Q.6. A primary and a secondary cell have the same e.m.f. Which of these will provide higher value of the maximum current?

Q.7. A coil' and a bulb arc connected in series with a 6 volt d.c. source. A soft iron core is then inserted' in the coil. What will happen to the intensity of the bulb?

Q.8. A convex bus on a screen forms the image of a candle. If the lower half of the bus in painted black to make it completely opaque, will the full size of image be obtained?

Q.9. A 4.5-cm needle placed 12 cm away from a convex mirror of focal length 1 5 cm. Give the location of the image and the magnification. Describe what hap- pens as the needle is moved farther from the mirror?

Q.10. What is solar constant and solar luminosity? How their knowledge helps us to find the surface temperature of sun?

Q.11. Is any work done by a magnetic field on a charge moving at right angles to the magnetic field? If not, how can it deflect the particle? If so, where does the energy come from?

Q.12. Two coherent sources of intensity ratio 'a' interfere. Prove that in the interference pattern

Q.13. How does a current carrying conductor coil behave like a magnet

Q.14. How is a necessary to use satellites for long distance T.V. transmission Why?

Q.15. How is a transformer used in long distance transmissions of a.c.?

Q.16. The angle of minimum deviation for prism of angle p /3 is p /6. Calculate the velocity in the material of the prism if the velocity of light in vacuum is 3 x 1 08 ms-1.

Q.17. Find the half-life of U238, if one gm of it emits 1.24 x 104 a particles per second.

Q.18. The gain of a common emitter amplifier is given by A = - gm RL. Does it mean that if we keep on increasing indefinitely RL, the gain of the amplifier will also increase indefinitely ? Explain your answer?

Q.19. Give construction of meter bridge. How can you measure unknown resistance of wire with the help of meter bridge.

Q.20. Two charges + 20 m C and -1 0m C are 20 cm apart. Calculate potential at a point P at a distance of 1 meter from either charge. Also calculate potential energy of a + 4m C charge placed at point P.

Q.21. Discuss the formation of energy bands in solids with one example.

Q.22. A steady current of 100 ampere is maintained in copper voltmeter. Calculate the time required to deposit 2.5 g of copper. Relative atomic mass of copper is 63.5.

Q.23. Draw a labelled diagram of Hertz experiment for generation of electromagnetic waves. How they were detected?

Q.24. Define half-life of radioactive substance. Derive an expression for it.

Q.25. Explain with diagram forward and reverse biasing in (i) n-p-n transistor and (ii) p-n-p transistor

Q.26. In the circuit given, calculate current in 3 W resistor and power loss in whole circuit.

Q.27. An electron is projected with the velocity of 105 m/s at right angle to the magnetic field

Of 0.019G. Calculate radius of circle Described by the electron.

Q.28. A conducting slab of thickness t (< d) is placed in a parallel plate capacitor. Derive an expression for the capacitance of the capacitor. OR

What is electric polarisation? Prove that the resultant electric field in a dielectric when placed between the plates of parallel plate capacitor is given by

E= Eo-(P/e o)

where E is the electric field in the absence of dielectric and P is polarization vector.

Q.29. What is photoelectric effect? Explain the effect of increase of (i) frequency (ii) intensity of the incident radiation on photoelectrons emitted by a phototube.

Q.30. A variable frequency 230 V alternating voltage source is connected across a series combination of L = 5 0 H, C = 80 m C and R = 40 W . Calculate (i) the angular frequency of source, which derives the circuit in resonance. (ii) Amplitude of the current at resonance frequency (iii) r.m.s potential drop across inductor at resonating frequency.