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Model Sample Paper - 8

Q.1. Why the picture on a T.V. screen shakes slightly when a low-flying aircraft passes overhead?

Q.2. Write two special characteristics of manganin due to which it is used is making standard resistances.

Q.3. A metal sphere of radius 1cm cannot hold a charge of 1 coulomb. Explain.

Q.4. Why is phosphorus bronze alloy preferred for the suspension wire of a moving coil galvanometer?

Q.5. It is easier to start car engine on a warm day then on chilly day. Why?

Q.6. A body weighs 90 kg on the surface of earth. How much does it weigh on a heavenly body whose mass is (1/9) th and radius (1/3) rd that the earth?

Q.7. If the earth did not have an atmosphere, would its average surface temperature be higher or lower than, what it is now?

Q.8. A primary and a secondary cell have the same e.m.f. Which of them will provide higher value of maximum current? Explain.

Q.9. A vessel is filled with two different liquids (non-mixing). One liquid is 50 cm deep and has refractive index 1.5 and other is 25 cm deep with refractive index 1.25. What is the apparent depth of the vessel when viewed normally?

Q.10. What type of V-1 graph is obtained in non-ohmic conductors? Illustrate with two examples.

Q.11. How polarization by reflection of waves takes place?

Q.12. Distinguish between (a) line (b) band and (c) continuous spectra.

Q.13. Certain characteristic wavelength in the light from a galaxy in the constellation Virgo are observed to increase in the wavelengths as compared with terrestrial sources by about 4%. What does this increase in wavelength indicate? Calculate the radial spread of galaxy. w.r.t. Earth.

Q.14. Two charges each of + q are placed along a line. A third change - 0 is placed in between them. At what position and for what value of Q will the system be in equilibrium?

Q.15. Explain how does resistivity of metallic conductors vary with temperature.

Q.16. What will happen to magnetic field due to a straight wire carrying current at any point as length of straight wire gives on increasing?

Q.17. Draw a graph to show the variation of stopping potential with frequency of radiations incident on a metal plate. How can the value of Plank's constant be determined from this graph?

Q.18. Which type of biasing results in very high resistance of p-n junction diode? Draw the diagram showing this.

Q.19. What is electro- deposition? Explain with example of electrolysis of copper sulphate.

Q.20. A 40 0 resistor, 3 mH inductor and 2 m F capacitor are connected in series of a 110 V, 50 Hz A.C. source. Calculate value of current in the circuit.

Q.21. With the help of a labelled diagram, describe Hertz experiment for the generation of electromagnetic waves.

Q.22. Distinguish between a metal, an insulator and a semiconductor on the basis of energy band diagram.

Q.23. What is the magnitude of the force on a wire of length 0 04-m placed inside a solenoid near its center making an angle of 300 with its axis. The wire carries a current of 12 A and magnetic field due to solenoid has magnitude of 0.25 T.

Q.24. A circular coil of 20 turns and radius I m carries a current of 1 A. Plane of the coil is perpendicular to external field 0.05 T. If a needle placed at the center of the coil vibrates with frequency of 2 Hz, calculate moment of inertia of the coil about the axis.

Q.25. Taking suitable example, explain mass defect of a nucleus.

Q.26. Distinguish between intrinsic and extrinsic semiconductors.

Q.27. Explain the working of a simple microscope and show that its magnifying power is given by

M= 1+(D/f), where f - focal length, D - least distance of distinct vision

Q.28. Derive an expression for instantaneous change at any time in a capacitive resistive circuit during (i) charging (ii) discharging

Q.29. What do you understand by artificial and induced radioactivity? The half-life of the radioactive radon is 3.8 days. Show that the time at the end of which - (1/20) of the Radon sample will remain undecayed is 16.5 days. OR

Explain the phenomenon of fusion. Give one representative equation. What are the conditions required for nuclear fusion to occur? What is the source of energy in the sun and the stars?

Q.30. Define electric field. A loop of wire of negligible thickness has a radius r and charge q is uniformly distributed over the loop. Find electric field E at a point P situated at a distance x from its center along its axis.