Download (www.efficientacademy.com)-ISC Physics Sample Paper 7

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Sample Paper
Class – XII
Subject – Physics
PART I ( Compulsory )
Question 1
a) What is the locus of a point at which potential due to an isolated point charge is constant?
b) What is Peltier’s effect?
c) Two electric bulbs are marked 220V., 60 W and 220 V, 100 W. Which bulb has more
resisatance?
d) Why Daniel cell is called standard cell?
e) A resistance wire of 20 ohm is bent in the form of complete circle. Find the resistance
between two points at right angles to each other.
f) What is the direction of induced magnetic field in magnetic substance whose relative
permeability is less than one?
g) A straight conductor of length 20 cm carrying current 2A is placed in a uniform magnetic
field 0.2T at an angle of 450 to the direction of field. What is the force on the wire?
h) W
i) How is an ideal inductor obtained?
j) What is meant by remote sensing?
k) A light ray moves from glass to water. What should be the value of critical angle for this
interface?
l) Visual angle of a distant star from nacked eye is 4’. What would be the visual angle of this
star from a telescope whose angular magnification is 12?
m) H
n) Sunlight rays when strike on sea surface at an angle of 420 from horizontal, gets completely
polarized after reflection. What is the refractive index of sea water?
o) What are atmospheric windows?
p) De broglie wavelength associated with an accelerated electron is 1.2A0. Calculate the
potential to which this electron is accelerated.
q) What is doping in semiconductors?
r) W
s) What is breeder reactor?
t) Draw the symbol for NOR gate.
PART II
SECTION A
( Attempt ant two questions from this section )
Question 2 a) An isolated helium particle ( + 2e ) is situated at the origin ( 0, 0 ). How much work
is done in taking a proton ( + e) from position ( 0, 4 ) to position ( 4, 0 ).
b) Given that the resistance of voltmeter is 400 ohm, find the voltmeter reading in the following
circuit diagram.
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c) Show that the radius of a charged particle entering perpendicularly in a magnetic field is directly
proportional to its momentum.
Question 3
a) State Gauss’s law. Use this law to derive formula for electric field intensity at a point due to a
uniformly charged plane sheet.
b) A freely suspended bar magnet completes 12 oscillations per minute in earth’s magnetic field ( H
= 3.6 x 10-4 T ) alone and 15 oscillations per minute when a small bar magnet with its axis
horizontal is placed near oscillating magnet. What is the magnetic field intensity produced by
second magnet?
c) Define Curie temperature. What is Curie temperature for steel?
Question 4
a) Find the inductance of the choke coil needed to run a lamp, with an ac source providing 100V
supply at 50 Hz. The lamp runs at 10 A current and has an effective resistance of 4 ohm.
b) What is th value of power factor in LC circuits. Write formula for frequency of LC oscillations.
What causes the damping of these oscillations?
c) State the principle of wheatstone bridge.
Other revision questions:
Q1).Two
wires of equal lengths are bent in the form of two loops.One of the loops is square shaped
w here as the other loop is circular.These are suspended in a uniform magnetic field and the same
current is passed through them.Which loop will experience greater torque?Give reasons.
Q2).When the cold junction of a certain thermo-couple was maintained at 20 degree C, its neutral
temperature was found to be 180 degree C. Find its temperature of inversion.
Q3).If the electric potential V is constant throughout a given region of space,what can you say
about the electric field E in that region?
Q4).A.d.c electric motor, operating at 30 V input is drawing a current of l0 A.The efficiency of the
motor is 40%. Calculate (i) the mechanical power output ,(ii) the energy lost as heat in 10 seconds
Q5). State how the magnetic susceptibility of a ferromagnetic change when it is heated?
Q6). Find the capacitance of the capacitor that would have a reactance of 100 ohm when used with
an a.c source of , frequency (5/π) kHz.
Q7).A thin converging lens of focal length 15 cm is kept in contact with a thin diverging lens of
focal length 20 cm. Find the focal length of this combination.
Q8).State Huygens' principle. Use it to derive Snell's law of refraction for a parallel beam incident
on the plane surface of a refracting medium. Give proper diagram.
Q9).A convex lens made of glass of refractive index µL is immersed in a medium of refractive
index µM How will the lens behave when µL< µM?
Q10). The half life of a certain radioactive element is 8 hours. if a pupli starts with 32 g of this
element, how much of the sample will be left behind at the end of one day?
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Q11).What is interference light? Write two essential conditions for sustained interference pattern to
be produced on the screen.W hat is the effect on the interference pattern in Young's double slit
experiment when:
(i) Screen is moved closer to the plane of slits?
(ii) Separation between two slits is increased Explain your answer in each case.
Q12). Why is a ray of light deviated by a prism? Draw a graph showing the variation of the angle
of deviation with the angle of incidence. Derive an expression for the refractive index of the
material of the prism in terms of its refracting angle and the angle of minimum deviation.
Q13). (a) An astronomical telescope consists of two convex lenses having focal length 80 cm and 4
cm. When it is in normal adjustment, what is its:
(i) Length,
(ii) Magnifying power?
(b) A convex lens of focal length 5 cm is to be used as a simple microscope. Where should an
object be kept so that image formed by the lens lies at least distance D of distinct vision (D=25
cm)? Also calculate the magnifying power of this instrument in this set up.
(c) What is meant by ‘Chromatic aberration’? A thin convex lens of focal length 30 cm and made
of flint glass (dispersive power = 0.03) is kept in contact with a thin concave lens of focal length 20
cm and made of crown glass. Calculate the dispersive power of crown glass if the above said
combination acts as an achromatic doublet.
Q14). a) Plot a labeled graph of |Vs| where Vs is stopping potential of photoelectrons versus
frequency ‘f’ of incident radiation. How will you use this graph to determine the value of Planck’s
constant? Explain.
(b) (i) Define ‘unified atomic mass unit’.
(ii) Find the minimum energy which a gamma ray photon should possess so that it is capable of
producing an electron positron pair.
(c) Fission of U – 235 nucleus releases 200 MeV of energy. Calculate the fission rate (i.e. no. of
fissions per second) in order to produce a power of 320 MW.