physics TU old questions (BSC.CSIT)
Physics TU old questions (BSC.CSIT)
Physics TU old questions (BSC.CSIT)
First Year/ First Semester
Subject : Physics I FM : 60
Time : 3 hours PM : 24
Candidates are required to give their answers in their own words as for s practicable.
The figures in the margin indicate full marks.
Year: 2065 physics model question bsc.csit
Section A
Long answer question
1. What is meant by Galilean invariance? Show that distance and acceleration are
invariant to Galilean transformation, velocity is not invariant. (2+1.5+1.5+2)
2. It is given that the potential energy of a system is rotationally invariant. What do
you mean by rotational invariance? Show that angular momentum is conserved for
such a system. (3.5+3)
3. (a) Discuss the analogy between liquid-flow and current-flow and hence, derive an
expression for liquid-flow through capillaries in series. (4)
(b) State Gauss’s law and use it to show that excess charge of a charged conductor
resides on its outer surface. (3) (3)
4. (a) Discuss the analogy between liquid-flow and current-flow and hence, derive an
expression for liquid-flow through capillaries in series. (4)
(b) State Gauss’s law and use it to show that excess charge of a charged conductor
resides on its outer surface. (3) (3)
5. Derive the expression for energy density in the magnetic field. (7) (7)
6. Explain the empirical basis for writing the Maxwell’s equations and write them. (7) (7)
Section B
Short answer Questions:
Answer any eight:
7. A proton is accelerated through a potential difference 50V and then it is allowed
cross a field free region 7.5m long. Find the time required to cross this distance. (4) (4)
8. Find the height of geostationary satellite (as viewed by an observer on the earth’s
surface); given g=9.8 ms-2
on the earth’s surface, R= 6.38 x 10
5m. (4) (4)
9. The potential energy for the Vander Waals force between two atoms is given by
, where x is the distance between the atoms and a and b are
positive constants. Calculate the force between the two atoms and plot it against x.(4) (2+2)
10. A parallel LCR circuit has L= 8mH, C= 10 µF and R= 0,5Ω. Calculate the natural
frequency and quality factor. (4) (2+2)
11. A water drop of radius 0.01 mm is falling through air neglecting the density of air as
compared to the water, calculate the terminal velocity of the drop ( ɳ for air = 1.8 x
10-4 CGS units) (4)
12. Two point charges of and -q/2 are located at the origin and at (a, 0, 0) respectively.
Find the point where electric field vanishes. (4) (4)
13. Two parallel conducting platees are separated by the distance d and potential
difference ᐃψ. A dielectric slab of dielectric constant k is and of uniform thickness
is tightly fitted between the plates. Find the electric field in the dielectric. (4) (4)
14. What is the capacitance of a capacitor that can store 800 J at 800 V? Suppose the
capacitor has parallel plates separated by 10-5 m and filed with a dielectric of
dielectric constant 2.2. What is the area of the plates? (4) (4)
15. Consider a simple RL circuit in which a sudden voltage V is applied. Discuss its
transient behavior and find the current as a function of time. (4)
16. Show that the time average power dissipation in a circuit which carries an AC
Year: 2066 physics model question bsc.csit
Section A
Long Answer Questions:
Answer any four:
1. Write the law of conservation of momentum and the law of conservation of energy.
Write Galilean transformation. Show that the laws of conservation of momentum
and of conservation of energy are invariant under Galilean transformation. (2+1+4)
2. Write and explain Bernoulli’s theorem giving two practical examples. Deduce
Bernoulli’s equation. (1+2±2+2)
3. (a) Given the sum of external forces acting upon a system of particles equals zero,
show that the total angular momentum remains constant. (4)
(b) Write Gauss’s law for a system of charges in vacuum. Modify this law for the
case when the some charges are in medium of dielectric constant K. (1.5+2)
4. Derive the expression for energy density in electric field. (7)
5. Derive
which constitutes one of the Maxwell’s equation. (7)
Section B
Short Answer Questions:
Answer any eight:
6. Calculate the magnitude of centripetal force acting on a mass 100g placed at a
distance 0.2m from the center of a rotating disk with 200 rpm. (4)
7. Given g = 9.81 ms2
, radius of earth = 6.38 x 106m and gravitational constant (G=6.6
x l0-11 m
3 Kg s-2
. Calculate the mass of the earth and time of revolution of asatellite
in a circular orbit near the earth surface. (2+2)
8. A charged particle moving along x — axis enters a region in which a constant
electric field is along y — axis and a constant magnetic field is along z — axis.
What is the condition that the net force acting on the charge is zero? (4)
9. A particle in Simple Harmonic Motion. Show that the total energy of the particle is
constant. (4)
10. In an experiment with Poiseuille’s apparatus the volume of water coming out per
second is 8 cm3
through a tube of length 0.62 m and of uniform radius 0.5 mm. The
pressure difference between the two ends of the tube is equal to 3.1 cm of Hg. You
can use the Poiseuille’s formula to calculate the coefficient of viscosity
(4)
11. Two point charges have charge q1= 2.0 x 10-8 C and q2=-0.7 x 10-8 C respectively.
The charges are placed 2 cm apart. Find force between the charges. (4)
12. An electron having kinetic energy 3.0 x 10-17 J enters a region of space containing a
uniform electric field E = 800 vm-1
. The field is parallel to the electron’s velocity
and decelerates it. How far does the electron travel before it comes to rest? (4)
13. A straight metal wire of length 1 is moved in a magnetic field b vector
with velocity v vector Consider the Lorentz force acting electrons in the wire and show that the potential difference across the wire is
14. A capacitor C, a resistor R and a battery arc connected in series with a switch. The
switch is closed at time t = 0. Set up the differential equation governing charge on
the capacitor and find the charge as a function of time. (4)
15. Calculate the energy density of uniform magnetic field of strength 1 Tesla in
vacuum- [µ0=4πx10-7 h/n] (4)
Year: 2067 physics model question bsc.csit
Section A
Long Answer Questions:
Answer any four:
1. A reference frame rotates with respect to another inertial reference frame with
uniform angular velocity w. The position, velocity and acceleration of a particle in
the inertial frame of reference is , and . Find the acceleration of the particle in
the rotating frame of reference.
3 a) State the assumptions made in deducing Stoke’s law for the motion of a small
sphere in a viscous medium. Use dimensional arguments to derive Stoke’s law.
(3.5)
b) Define dipole moment and derive expression for electric field of a dipole. (3.5)
4. Discuss and derive the boundary conditions imposed on the field vectors and
at the interface of two dielectric media. (7)
5. Use Maxwell’s equations to derive wave equation for electric and magnetic field.
(7)
Section B
Short Answer Questions:
Answer any eight:
7. An electron describes a helix of radius 0.2 m and pitch 0.03 cm in a magnetic field
of 50 gauss(104 gauss = 1 Tesla). Calculate the components of its velocity alloy and
Perpendicular to the field. (4)
8. A satellite of m is revolving around the earth in a circular orbit of radius r = R + h,
where R is the radius of the earth and h is the height of the satellite above earth’s
surface. Calculate the angular momentum of the satellite about the center of the
earth. (4)
9. An LC circuit oscillates with a frequency of 200 Hz. The capacitance in the circuit
is 10 µF. What is the value of the inductance? (4)
10. Two horizontal capillary tubes A and B are connected together in series so that a
steady stream of liquid flows through them. A is 0.4 mm in internal radius and 250
cm long while B is 0.3 mm in internal radius and 40 cm long. The pressure of the
fluid is 7.5 cm of Hg above the atmospheric pressure at the entrance point of A. At
the exit point of B the pressure is atmospheric (76 cm of Hg). What is the pressure
at the junction of A and B? (4)
12. A plane slab of material with dielectric constant K has air on both sides. The electric
field in air is E0 and it is uniform and perpendicular to the boundaries. Find the field
inside the dielectric. (4)
13. Two identical air capacitors are connected in series and the combination is
maintained at a constant voltage 50v. A dielectric sheet of dielectric constant 6 and
thickness equal to the –sixth of the air gap is now inserted into one of the capacitors.
What is the voltage across that capacitor? (4)
14. Show that magnetic field energy of a system of currents is given by
where
J is current density, A is vector potential and dv is the volume element. The integration is carried over volume. (4)
15. A capacitor C, a resistor R and a battery of voltage V0 are connected in series with a
switch. The switch is closed at time t =0. Set up the differential equation for charge
of on the capacitor and determine it as a function of time. (4)
Year: 2068 physics model question bsc.csit
Section A
Long Answer Questions:
Answer any four:
1. What are non-inertial frames of reference? Define and explain centrifugal and
Coriolis forces. (2-1.2+3)
2. State and explain law of conservation of angular momentum. Also state and explain
Kepler's 2nd law. (1+2+1+3)
3. What do you mean by a harmonic oscillator? Discuss the oscillation of diatomic
molecule. Hence sketch the energy level diagram. (2+4+1)
4. Discuss the boundary conditions on the field vectors E and D? (3.S+3.5)
5. Explain the meanings of power and power factors. Further discuss the phenomena
of resonance and hence obtain quality factor. (2+2+2+1)
Group B
Short Answer Questions:
Answer any Eight:
6. A proton is accelerated through a p.d. 50 and then it is allowed to cross a field free r
ion 7.5m long. Find the time required to cross this distance. (4)
7. The intial positions of two particles are (-2, 0) and (0, -2) and they start
simultaneously along the axes of x and y with uniform velocities 3i cm/s and 4j
cm/s respectively. Obtain the vector representing the position of the 2nd particle
with respect to the first as a function of time.- (4)
8. Show that the force defined by F = („2 x2 + 2xyj is conservative. (4)
9. A particle of mass 5 gm lies in a potential field V = (8x2 + 200) ergs/gm. Calculate
its time period. (4)
10. Calculate the mass of water flowing in 10 minutes through a tube 0.1 cm in
diameter 40 cm long, if there is a constant pressure head of 20 cm of water. (11 for
water = 0.0089 cgs units). (4)
11. Two small identical conducting spheres have charges of 2.0 x 10-9 C and -0.5 x10"
C, respectively. When they are placed 4 cm apart, what is the force between them?(4)
12. Find the electric field produced by a uniformly polarized sphere of radius R. (4)
13. Find the energy of a uniformly charged spherical shell of total charge 9 and radius
R. (4)
14. A real capacitor C has a parallel leakge resistance R; it is connected in series with
an ideal inductance L. Calculate JZI; find the approximate values at high and low
frequencies assuming R is large. (2+2)
15. Calculate the energy density of uniform magnetic field of strength I Tesla
invacuum. (p0=4 x1o7Ns2/z)
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