» CBSE PHYSICS Board Paper, 1998 Supplementary : CBSE Sample Question Papers

1. How does the luminosity of a star vary with its mass ? 1
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2. State two factors by which the range of transmission of signals by a T.V. tower can be
increased. 1
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3.The ratio of the horizontal component to the resultant magnetic field of earth at a given place
is 1/√2 . What is the angle of dip at that place ? 1
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4. Why is a dark region observed in a discharge tube at very low pressures ? 1
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5. What is the ratio of the nuclear densities of two nuclei having mass numbers in the ratio 1:4?
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6. If the frequency of the a.c. source in a LCR series circuit is increased, how does the current in the circuit change ? 1
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7. What is the work done in moving a 2 microcoulomb point charge from corner A to corner B of a square ABCD when a 10 µC charge exists at the centre of the square ? 1

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8. Why is the terminal voltage across a battery more than its e.m.f. during re-charging ? 1
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9. An electric flux of -5 x 10³ Nm² C ^-1 passes through a spherical Gaussian surface of radius 20 cm due to the charge placed at its centre.
(i) Calculate the charge enclosed by the Gaussian surface. 1
(ii) If the radius of the Gaussian surface is doubled, how much flux would pass through the surface ? 1
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10. The variation of resistance of a metallic conductor with temperature is given below.
(i) Calculate the temperature coefficient of resistance from the graph. 1
(ii) State why the resistance of the conductor increases with rise in temperature. 1

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11. Three identical cells, each of e.m.f. 2 V, are connected in parallel. This combination is connected to a 5 ohm resistor. If the terminal voltage across the cells in the closed circuit is 1.5 V, calculate the internal resistance of each cell. 2
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12. Using Stefan’s Law, explain briefly how the surface temperature of a planet can be measured. 2
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13. Define resolving power of a telescope. How does diffraction limit its resolving power ? 2
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14. Define the terms (i) luminous intensity and (ii) illuminance. Write the relation between them.
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15. An irregular shaped wire PQRS (as shown in figure) placed in a uniform magnetic field perpendicular to the plane of the paper changes into a circular shape. State, with reason, the direction of the induced current in the loop. 2

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