TIFR GS 2025 Question Paper Physics IPhD

FOR TIFR GS EXAM PREPARATION

TIFR GS 2025
Question Paper ·
Physics
EXAM YEAR TYPE SUBJECT DETAILS

TIFR GS 2025 Question Paper Physics IPhD

Notes · Sample Papers · Previous Year Papers · Mock Tests

m
m .co

m .co s e m
se g l a
a
Section A
A1 Consider the triangle subtended on the surface of a sphere of radius 1 by joining the
1 √3 1 √3
points ( , , 0), (− , , 0), and (0, 0, 1) with arcs of great circles. The area
2 2 2 2

m
subtended by this triangle on the surface of the sphere is given by:

m .co
.co
(Hint: Drawing a figure might help.)
e m
e m l as
s
(a) a /3
l ag
ag
(b) √3 /2

(c) √3

m
(d) 2 /3
m .co
s e
g la
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 1 of 40

A2 The Figure on the right shows a regular
pentagon. The black solid circles on its
vertices represent point charges with
charge – . There is no charge at the
position of the white circle at (measured r
from the origin, O, placed at the centre of
the pentagon). The electric field at O is
given by:

(a) −
=
4 0 3

(b) −4
=
4 0 3

(c)
= 3
4 0

(d) −4 (sin ̂ + cos ̂)
= 10 10
4 2
0

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 2 of 40

m
m .co

m .co s em
se g la
A3
a
Consider a two dimensional insulating solid crystal. At low temperature, how does
ℰ
the specific heat at constant area = , where ℰ is the energy per unit area,
depend on ?

2
(a) ∼
m
m .co
(b) ∼ .co
3
s e m
s em l a
g la ∼ ag
a
(c)

(d) is independent of

m
m .co
s e
g la
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 3 of 40

A4 The Figure below shows a rocket (red arrow) launched from the earth which is now
at a point where the Earth’s gravitational field is negligible. The rocket thrusters
have stopped. In the rest frame of the Sun, the velocity of the rocket at is same in
magnitude but opposite in direction to that of the earth was, when it was at the same
point. Which of the following statements is correct?

−

(a) The rocket will move exactly on the earth’s elliptical orbit shown in the figure
and eventually collide with the earth

(b) The rocket will eventually escape the Sun’s gravitational field

(c) The rocket will eventually reverse its direction and follow the earth

(d) The rocket will turn towards the sun and eventually collide with it

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 4 of 40

m
m .co

m .co s e m
se g l a
A5 Water is flowing out of a small horizontal
a
opening of area, , at the bottom of a tank
of height . The flow is a laminar flow H
under the influence of gravity. What is
the area, ′ , of the stream transverse to A
the fluid velocity, at a height ℎ below the h
A’
m
opening? (Neglect atmospheric pressure

m .co
and dissipation effects. The thickness of

.co e m
the stream is negligible compared to
and ℎ.)
em l as
l as ag
g
a(a)
√
ℎ+

(b)
ℎ+

m
m .co
(c) ℎ
(1 + ) s e
g la
a
(d)
ℎ
√1 +

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 5 of 40

A6 A small metallic wire with mass and
electric resistance is bent into a closed
square shape with sides . It passes
through a region of length > with
0
magnetic field ̂ . The initial velocity
0 ̂ of the square is large enough that it
emerges out of from the right. What is
the final velocity of after it completely
emerges from ?

(a) 3 2 2

0 (1 − ) ̂
0

2 2
(b) −
0 0 ̂

(c) 3 2
0 (1 − )̂
0

(d) 0̂

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 6 of 40

m
m .co

m .co s e m
se g l a
A7 The output pulse train Y of the circuit
a
shown on the right, with three
synchronized input trains,

= 00001111

= 00110011

m
.co
= 01010101
m
will be: .co s e m
s em l a
g la00010111 ag
a
(a)

(b) 00100111

(c) 01010101
m
m .co
(d) 00010001
s e
g la
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 7 of 40

A8 (NB: Due to a typo in the options all test takers will be awarded the full score.)

Consider a stationary electron in a uniform, time-independent magnetic field of
strength 0 /4 oriented in the ̂ -direction. The Hamiltonian for this system is
expressed as

=− .

where is the spin-1/2 operator for electrons. The initial electron spin is oriented in
the ̂-direction. The spin precession frequency of the electrons is:

(a) | | 0
4

(b) | | 0
8

(c) | | 0
2

(d) 0

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 8 of 40

m
m .co

m .co s e m
se g l a
A9 Consider the following space-
a
time diagram which indicates
three events , and for an
inertial observer. Which of the
following statements is true?

m
m .co
m .co s e m
s e l a
g l a ag
a
(a) It is always possible to find an inertial observer for whom events and are
simultaneous. However, no inertial observer can be found for whom events
and are simultaneous.

m
.co
(b) It is always possible to find an inertial observer for whom events and are
simultaneous. However, no inertial observer can be found for whom events
and are simultaneous.
s em
g la
a
(c) It is always possible to find an inertial observer for whom events and are
simultaneous. Similarly, an inertial observer can also be found for whom
events and are simultaneous.

(d) It is impossible to find an inertial observer for whom events and are
simultaneous. Similarly, no inertial observer can be found for whom events
m
m and are simultaneous.
.co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 9 of 40

A10 A massless rigid rod of length is
suspended with an ideal spring of spring
constant at one end , and by a hinge
on the other end, . The rest length of the
spring is zero. A mass is suspended
from the mid-point of the rod. This results
in tilting of the rod by angle . What is
the angle ?

(a) tan−1 ( )
2

(b) sin−1 ( )
2

(c) cos−1 ( )

(d) sec −1 ( )

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 10 of 40

m
m .co

m .co s e m
se g l a
A11 There is an open window of dimension
a
(Top view)
1m × 1m on the north east ( ) facing
wall of a house. At 9 AM, the sun shines
through the window and illuminates a Sun rays
certain part of the floor of the house.
What is the area illuminated by the

m
sun? (Assume that the sun rises in the

.co
east ( ) at 6 AM and is directly overhead
m
.co m
( ̂ ) at 12 noon.) ̂
s e
s em l a
(a) la 1 ag
ag √2 m
2

(b) 1 m2

(c) 1 2
m
2
m
m .co
s e
√2 m2
la
(d)

ag

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 11 of 40

A12 For a one dimensional quantum harmonic oscillator, at time = 0, the particle is in
the ground state. What is the expectation value of the position and momentum
operator at time ?

(a) 〈 ( )〉 = 〈 ( )〉 = 0

(b) ℏ
〈 ( )〉 = √ sin , 〈 ( )〉 = 0

(c) ℏ
〈 ( )〉 = √ sin , 〈 ( )〉 = √ℏ cos

(d) 〈 ( )〉 = 0, 〈 ( )〉 = √ℏ cos

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 12 of 40

m
m .co

m .co s em
se g la
a and respectively such
A13 Consider two ideal gases and with atomic masses
that > . The two gases with same number of moles are kept at the same
temperature and confined in containers with the same volume. Which of the gases
will exert more pressure and molecules of which gas will have a higher RMS
momentum?

m
m .co
(a) .co
Both will exert the same pressure but molecules of Gas will have more
s e m
s em
RMS momentum
l a
g la ag
a(b) Gas will exert more pressure and molecules of Gas will have more RMS
momentum

(c) Gas will exert more pressure but molecules of Gas will have more RMS
momentum

o m
c
. molecules of both gases have the same
m
(d) Both will exert the same pressure and
e
RMS momentum
la s
ag

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 13 of 40

A14 For a given measurement of particles in a counter, a 10-minute data collection
resulted in a statistical uncertainty of 2.5%. How much additional time must be
allocated to reduce the statistical uncertainty to 0.5%?

(a) 240 minutes

(b) 40 minutes

(c) 250 minutes

(d) 50 minutes

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 14 of 40

m
m .co

m .co s em
se g la
a
A15 Laser light is incident normally on a thin film of material with a refractive index
( ) larger than that of air ( ≈ 1). As the wavelength of the laser light is varied,
the intensity of the transmitted light through the film shows a peak at 633 nm. If the
thickness of the film is 118 nm, the minimum is closest to:

(a) 2.68
m
o m m .co
(b) 5.36 .c e
em l as
l as ag
g
a(c) 1.34
(d) 3.68

m
m .co
s e
g la
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 15 of 40

A16 The asymptotic expansion of the following function for →∞
1
tanh−1

is given by:

(a) 1 1 1
1+ 2
+ 4
+ +⋯
3 5 7 6

(b) 1 1 1
1− 2
+ 4
− +⋯
3 5 7 6

(c) 1 1 1
+ + 3 + 5 +⋯
2 4 6

(d) 1 1 1
1+ 2
+ 4
+ +⋯
2 4 6 6

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 16 of 40

m
m .co

m .co s e m
se g l a
a
A17 The × ( > 4) matrix , with all entries equal to 1 has:

(a) Precisely − 1 degenerate eigenvalues and one other non-degenerate
eigenvalue
m
m .co
.co
(b) Precisely − 2 degenerate eigenvalues and two other non-degenerate
s e m
s em
eigenvalues
l a
g la ag
a(c) Precisely 2 degenerate eigenvalues and − 2 other non-degenerate eigenvalues

(d) No degenerate eigenvalues

m
m .co
s e
g la
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 17 of 40

A18 A spaceship is moving with a constant
relativistic velocity ̂′ with respect to
an inertial frame ′. In the frame
moving with spaceship, light is emitted
from the source and is detected at the ℎ
detector with displacement ℎ ̂ from . ′
In the frame ′ , what is the time ’ taken
′
for the light to reach from to ? ′

(a) ℎ
( )
√1 − 2/ 2

(b) ℎ
( ) √1 − 2/ 2

(c)
ℎ 1− /
( )√
1+ /

(d) ℎ
( )

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 18 of 40

m
m .co

m .co s e m
se g l a
A19 The sinusoidal signal
a
= sin(2 )

is given to a high-pass filter (see Figure).
The output signal is given by

= | |sin(2 + ).
m
m .co
.co
What is the value of | |?
e m
em l as
l as ag
a g
(a) 1
2 1⁄2
1
|1 + ( ) |
2

(b) 1
1
|1 + ( )|
2
m
m .co
(c) 1
s e
|1 + (
1 2
) |
g la
2
a
(d) 1
1⁄2
1
|1 + (2 )|

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 19 of 40

A20 For the circuit on the right, which graph
represents correctly for the
shown below?

(a)

(b)

(c)

(d)

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 20 of 40

m
m .co

m .co s e m
se g l a
A21 Light in medium with electric
a
permittivity and magnetic
permeability is incident on a
medium with electric permittivity ′
and magnetic permeability ′. The
angle of incidence is . The field

m
is linearly polarized in the plane as

.co
shown, and the field is in the ̂
m
.co e m
direction. Which of the following is

em
a correct boundary condition on the
l as
as
fields?
l ag
ag
′
(a) ( sin + ′′ sin ) = ′ sin

(b) ( cos − ′′ cos ) = ′ ′ cos

m
.co
(c) sin + ′′ sin = ′ sin

e m
( + ′′ )
= ′
′ las
g
(d)
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 21 of 40

A22 An experimental set-up needs to be kept in an environment with zero magnetic field
by minimizing the Earth’s magnetic field. This can be achieved by:

(a) Keeping the setup in a place completely covered with a sheet of metal of very
high magnetic permeability

(b) Keeping the setup in a place completely covered with a sheet of metal of very
high permittivity

(c) Keeping the setup at the centre of the interior of a long solenoid

(d) Keeping the setup in a place completely covered with a sheet of an insulating
material

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 22 of 40

m
m .co

m .co s em
se g la
a
A23 Two types of particles and have the same mass, but are distinguished by an
internal degree of freedom. A classical ideal gas in a volume at temperature
contains ( ) 2 particles of -type and ( ) particles of -type and particles
of -type. Which of the following is true?

m
.co
(a) Pressure of ( ) and ( ) are same; ( ) has more entropy than ( )
m
.co s e m
s em l a
g laPressure of ( ) and ( ) are same; ( ) has more entropy than ( ) ag
a
(b)

(c) Pressure of ( ) is greater than pressure of ( ); ( ) has more entropy than
( )

o m
c
. of ( ); ( ) has more entropy than
m
(d) Pressure of ( ) is greater than pressure
e
( )
la s
a g

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 23 of 40

A24 (NB: Due to an ambiguity in the question all test takers will be awarded the full
score.)

A negative electric charge − moves in a (classical) circular orbit at a non-relativistic
speed around a positive charge. The magnetic field at the centre of the circular orbit
due to the negative charge is found to be 1. Now, consider another situation where
a negative charge −2 moves in a circular orbit at the same speed around the same
positive charge. The magnetic field at the centre of the circular orbit in this case is
2 . What is the ratio 2 / 1 ?

(a) 1/2

(b) 1

(c) 2

(d) 4

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 24 of 40

m
m .co

m .co s e m
se g l a
A25 Consider a fan with blades rotating with
a
frequency , as shown in the Figure. It
is used to periodically block a light
beam of intensity 0 . The beam has a
very small cross-sectional area and hits
the blade near its outer edge, as shown.

m
The transmitted beam is detected by a

m .co
photo-detection unit which gives out a

.co m
voltage signal proportional to the

m s e
transmitted intensity . If this voltage
s e l a
a ag
signal pattern is displayed on an
g l
oscilloscope, what would best describe
athe signal pattern?

(a) 1 4
0[ +∑ sin(2 )], = 2,6,10,14 …
2

m
c. o)],
(b) [cos2 (2 ) − sin2(2
0 ∑ = 2,6,10,14 …

e m
las
g
[ + sin(4 a)]
(c) 1 1
0
2 2

2
(d) 0 [cos (4 )]

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 25 of 40

Section B
B1 Let | 〉 denote the energy eigenstates of nonrelativistic hydrogen atoms without
spin, and 0 is the Bohr radius. The matrix element

〈 = 2, = 1, = 0| ̂| = 2, = 0, = 0〉

is:

(a) 0

(b) √2 0

(c) 0

(d) √3 0

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 26 of 40

m
m .co

m .co s e m
se g l a
B2 The given Figure shows some
a
charges and their coordinates in
the − plane. The electric
potential at a point, , far from the
origin, is given by:

m
m .co
m .co s e m
s e l a
g l a ag
a

(a) ( . ̂ + 2 . ̂)
ϕ=
4 0 3

m
.co
(b)
ϕ=
4 0
2
e m
las
(c) d .̂ ag
ϕ= 3
4 0

(d) .̂
ϕ= 3
4 0

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 27 of 40

B3 Consider a massless string with one end
fixed on the ceiling ( ). The total length
of the string is and it is initially
completely wrapped around a solid
uniform disc of radius (assume ≪ )
and mass . The disc is released from
rest from the ceiling at time = 0 and
falls under gravity. The thread unwinds
from the disc, always remaining tight.
What is its velocity at a time before the
thread unwinds fully?

(a) 2
− ̂
3

(b) − ̂

(c) 3
− ̂
4

(d)
− ̂
2

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 28 of 40

m
m .co

m .co s em
se g la
B4
a
A quantum particle is in the ground state of an infinite potential well of length with

0 for ∈ [0, ]
( )={
+∞ otherwise
What is the expectation value of the operator,

̂ = ̂ ̂ + ̂̂
m
in this state?
m .co
m .co s e m
s e l a
(a)
g l a0
ag
a
(b) ℏ

(c) ℏ/2

m
.co
(d) −ℏ

e m
las
ag

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 29 of 40

B5 Consider a random walker on a 2D plane which starts at the origin. At every step it
either moves one unit along the positive -axis with probability 1/2 or along the
positive -axis with probablity 1/2. The distance from the origin after steps is
denoted by . What is the mean square displacement 〈 2 〉?

(a) ( + 1)/2

(b) ( − 1)/2

(c) 2

(d) ( − 1)

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 30 of 40

m
m .co

m .co s e m
se g l a
B6 Consider a quantum particle of mass m in
a
an infinite one-dimensional potential well
of length L between points A and B. The
particle is in the ground state with an
energy . The wall at B is suddenly
shifted to B’ where AB’ has length 2L.

m
We measure the energy again, and obtain

.co
the value 1 . what is the probability that
m
1 ≠
.co e m
?

e m l as
as
l1 ag
g
a 2
(a)

(b) 1
4

m
.co
(c) 1

e m
0 las
g
(d)
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 31 of 40

B7 A ball is dropped on the floor from
height ℎ. It bounces up to height ℎ/4 on
the first bounce. Now identical balls
and are dropped together from height
ℎ as shown. How high does the ball
bounce on the first bounce? Assume that ℎ
the coefficient of restitution between
balls and is 1. (Ignore the size and the
small initial separation of the balls.)

(a) ℎ/4

(b) ℎ

(c) ℎ/2

(d) ℎ/8

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 32 of 40

m
m .co

m .co s em
se g la
B8
a
Consider a spherical planet with a radius = 6400 km. The density ( ) for varies
as ( ) ∝ , where is the distance from the centre of the planet. A tunnel is dug
through the centre, and the escape speed is measured at various distances . At the
planet’s surface, the escape speed is found to be 11.2 km/sec, and at a distance of
3200 km from the centre, it is 12.7 km/sec. What is the escape speed at the centre of
the planet?

m
m .co
.co m
(a) 12.9 km/sec
s e
s em l a
(b)la14.2 km/sec ag
ag
(c) 13.2 km/sec

(d) 0 km/sec

m
m .co
s e
g la
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 33 of 40

B9 There is a uniform electric field ̂
between two parallel plates of a
capacitor (parallel to the plane). The
plates are placed in a uniform magnetic
field ̂ which fills the entire region
(inside and outside the capacitor).
Charged particles enter the capacitor
through a small aperture . They exit
from a small aperture ′ at the other end,
if they do not deviate from a straight line ′
path. There is a detector plate in the
plane passing through ′. detects ̂
⃗
where the particles impinge. What is the
displacement vector ⃗ between the
impact point and the aperture ′ for a
particle with mass and charge ?
(This device is a simple version of a
mass spectrometer.)

(a) −2
2
̂

(b) −
2
̂

(c) −
2
̂
2

(d)
2
̂

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 34 of 40

m
m .co

m .co s em
se g la
a
B10 A stream of electrons, each having an energy of 0.5 eV, impinges on a pair of
extremely thin slits separated by 10 μm. The distance between adjacent minima on a
screen 20 m behind the slits would be closest to:

(a) 3.48 mm

m
m .co
.co
(b) 1.74 mm
e m
e m l as
(c) a
l s
6.96 cm ag
ag
(d) 5 m

m
m .co
s e
g la
a

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 35 of 40

B11 A very long square pipe with length
and cross-sectional area 2 ( ≫ ) has
ideal conducting walls. A travelling
mode with

−
( ⃗, ) = sin sin

is excited in the pipe. What is the
relation between and ? (Assume ≈
0 , ≈ 0 .)

(a) 2 2 2
=√ 2 − 2

(b) 2 2 2
=√ 2 + 2

(c) =

(d) 2 2
=√ 2 + 2

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 36 of 40

m
m .co

m .co s e m
se g l a
B12 The general solution of the equation
a
3
3
3
+ = 0 ( > 0)

is given by::

(a)
m
.co
−
1 + 2 2 cos(√3 /2) + 3 2 sin(√3 /2)
m
m .co s e m
se l a
(b) la − −
ag
ag
−
1 + 2 2 cos(√3 /2) + 3 2 sin(√3 /2)

(c) −
1 + 2 2 cos(√3 /2) + 3 2 sin( /2)

m
(d) −
+ 2 cos( /2) + .co
2 sin(√3 /2)
em
1 2 3

l as
ag

m
m .co
m .co s e m
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 37 of 40

B13 Radiation from the Big-Bang observed today has a black-body spectrum with =
2.7 K and its energy density as a function of the wavelength peaks at = 1.1 mm.
This radiation is red-shifted to longer wave lengths compared to the black-body
spectrum when the universe was hotter, say at 270 K. What was the photon energy
corresponding to the wavelength at which the energy density peaked, when the
universe was at 270 K?

(a) 0.12 eV

(b) 1.2 meV

(c) 23 meV

(d) 0.23 eV

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 38 of 40

m
m .co

m .co s e m
se g l a
B14 Consider the Collector-Emitter
a
characteristics of a silicon NPN transistor in
the Figure below. The circuit on the right is
for lighting an LED with an input voltage
= 1V. The LED needs 20mA current,
that will be provided by the transistor. A
forward biased silicon PN junction has a
m
.co
0.7V drop across it. What is the closest value
m
.co m
of resistor needed for this purpose?

m s e
s e l a
g l a ag
a

m
m .co
s e
g la
(a) 1.3 Ω a
(b) 560 Ω

(c) 4.2 Ω

m
m .co
.co m
(d) 15 Ω

m s e
s e g l a
g la a
a

m .
.co s e m
s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 39 of 40

B15 A classical ideal gas at temperature is placed in a spherically symmetric potential

( )= 3

What is 〈 ( )〉 per particle?

(a)

(b) 3 /2

(c) /2

(d) /3

For more Question Papers, Sample Papers, Notes & Syllabus visit Page 40 of 40