CBSE Physics
Previous Question Paper
All India (Comptt.) 1998 (Part - 8)
Q. 1. Name the physical quantity whose SI unit is Coulomb/Volt.
Q. 2. Write the frequency limit of visible range of
electromagnetic spectrum in kHz.
Q. 3. How does the conductance of a semi-conducting
material change with rise in temperature?
Q. 4. The force F experienced by a particle of charge e
moving with velocity v in a magnetic field B is given by Of these, name the
pairs of vectors which are always at right angles to each other.
Q. 5. Two wires A and B are of same metal, have the same
area of cross-section and have their lengths in the ratio 21. What will be
the ratio of currents flowing through them respectively when the same
potential difference is applied across length of each of them?
Q. 6. Calculate the rms value of the alternating current
shown in the figure.
Q. 7. The image of an object formed by a lens on the
screen is not in sharp focus. Suggest a method to get clear focusing of the
image on the screen without disturbing the position of the object, the lens
or the screen.
Q. 8. Two protons A and B are placed between two
parallel plates having a potential difference V as shown in the figure. Will
these protons experience equal or unequal force?
Q. 9. Define the terms ‘threshold frequency’ and
’stopping potential’ for photo-electric effect. Show graphically how the
stopping potential, for a given metal, varies with frequency of the incident
radiations. Mark threshold frequency on this graph.
Q. 10. Draw labelled diagram of a Leclanche cell. Write
the function of charcoal powder and manganese dioxide used in its porous
pot.
Q. 11. How does the mutual inductance of a pair of coils
change when
(i) the distance between the coils is increased ?
(ii) the number of turns in each coil is decreased ?
Justify your in each case.
Q. 12. Define the terms magnetic inclination and horizontal com¬ponent of Earth’s magnetic field at a place. Establish the relationship between the two with the help of a diagram.
Q. 13. An electron in an atom revolves around the
nucleus in an orbit of radius 0.53 A. Calculate the equivalent magnetic
moment if the frequen¬cy of revolution of electron is 6.8 x 109
MHz.
Q. 14. Write the function of base region of a
transistor. Why is this region made thin and slightly doped?
Q. 15. Derive an expression for the energy stored in a
charged parallel plate capacitor with air as the medium between its plates.
Q. 16. In the diagram given below for the stationary
orbits of the hydrogen atom, mark the transitions representing the Balmer
and Lyman series.
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
.
Q. 18. Two point electric charges of values q and Iq 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 q and d.
Q. 19. Explain, with the help of a circuit diagram, the use of
potentiometer for determination of internal resistance of a primary cell.
Derive the necessary mathematical expression.
Q. 20. (i) Sketch the wave-fronts corresponding to converging
rays. (ii) Verify Snell’s law of refraction using Huygens’ wave theory.
Q. 21. An electric dipole is held in a uniform electric field.
(i) Show that no translator}’ force acts on it
(ii) Derive an expression for the torque acting on it
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
increase in width of the slit?
Q. 23. A capacitor of capacitance 100 μF and a coil of resistance 50Ω and inductance 0.5 H are connected in series with a 110V, 50 Hz source. Calculate the rms value of the current in the circuit.
Q. 24. Draw a labelled ray diagram to show the image formation in
a reflecting type telescope. Write its two advantages over a refracting type
telescope. On what factors does its resolving power depend?
Q. 25. Define the terms ’solar constant’ and ’solar luminosity’. Explain how their knowledge helps us to calculate the surface temperature of the sun. Derive the necessary mathematical expression.
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.
Q. 27. A voltmeter V of resistance 400 Ω is used to measure
the potential difference across a 100 Ω. resistor in the circuit shown
here.
(a) What will be the reading on the voltmeter?
(b) Calculate the potential difference across 100 Ω resistor before
the voltmeter is connected.
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?
Derive a mathematical expression for the force acting on a
current carrying straight conductor kept in a magnetic field. State the rule
used to determine the direction of this force.
Q. 29. (i) Draw a labelled diagram of Thomson’s
experimental set-up to determine e/m of electrons, (ii) Explain, by deriving
the necessary mathematical expression, how e/m of electrons can be
determined by this method.
Q. 30. Define the terms ‘potential barrier’ and
‘depiction region’ for a p-n junction. Explain, with the help of a
circuit diagram, the use of a p-n diode as a full wave rectifier. Draw the
input and output wave-forms.