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Physics
Class- XII
2000(CBSE)
You are on Set no 2 Qno. 1 to
30
Time allowed
: 3 hours
Maximum Marks : 70
General Instructions :
(i)
All questions are compulsory.
(ii) Marks for each question are
indicated against it.
(iii) Question number 1 to 8 are very
short-answer questions each of 1 mark. Answer them in about one sentence
each.
(iv) Question number 9 to 18 are short-answer questions of 2
marks. Answer them in not more than 30 words each.
(v) Question number
19 to 27 are short-answer questions of 3 marks. Answer them in not more
than 50 words each.
(vi) Question number 28 to 30 are long-answer
questions of 5 marks each. Answer to these questions should be around 150
words each.
(vii) Use Log Tables, if necessary.
(viii) Please write
down the serial number of the question before attempting it.
Q1)
Draw an equipotential
surface for a point charge Q > 0. (Marks 1)
Q2)
If the ratio of the
horizontal component of earth's magnetic field to the resultant magnetic
field at a place is 1/ 2, what is the angle of dip at that place ? (Marks
1)
Q3)
How does the energy gap
in an intrinsic semiconductor vary, when doped with a pentavalent impurity
? (Marks 1)
Q5)
Why is the transmission
of signals using ground waves, restricted only to a frequency of 1500 kHz
? (Marks 1)
Q9)
Four capacitors are
connected as shown in the figure given below :
Calculate the equivalent
capacitance between the points X and Y. (Marks 2)
Q10)
Draw the logic symbol of
a 2 - input NOR gate. Write down its truth table. (Marks
2)
Q13)
If the wavelength of
incident light on a (i) concave mirror, and (ii) convex lens is increased,
how will the focal length of each of these change ?
(Marks
2)
Q19)
With the help of a
labelled circuit diagram, explain how will you compare the e.m.fs of two
primary cells using a potentiometer. State the formula used.
(Marks 3)
Q21)
State how in a photocell
the work function of the metal depends on the kinetic energy of emitted
electrons. If the frequency of the incident radiation is doubled what
changes occur in the (i) stopping potential, and (ii) photoelectric
current. (Marks 3)
Q26)
A short bar magnet of
magnetic moment 0.9 joule/ tesla is placed with its axis at 30o
to a uniform magnetic field. It experiences a torque of 0.063 joule (i).
Find the strength of the magnetic field, and (ii) what orientation of the
bar magnet corresponds to the stable equilibrium position in the magnetic
field ? (Marks 3)
Q28) For a given a.c circuit
distinguish between resistance, reactance and impedance. An a.c source of
50 hertz frequency is connected to an 100 mH inductor and a bulb. The bulb
glows with some brightness. Calculate the capacitance of the capacitor to
be connected in series with the circuit for which the bulb will glow with
maximum brightness. (Marks 3+2)
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