Federal Public Service Commission (FPSC)
Competitive Examination for Recruitment to BPS-17 Posts under the Federal Government
Paper: Physics
Time Allowed: 3 Hours
PAPER-I (Subjective) 80 Marks
PART-II
Attempt ONLY FOUR questions from PART-II, ALL Questions carry EQUAL marks.
Q. No. 2.
(a) Explain the divergence of a vector field with its physical significance.
(b) A rural mail carrier leaves the post office and drives 22.0 km in a northerly direction. He then drives in a direction 60.0° south of east for 47.0 km. What is his displacement from the post office?
(c) Vectors C⃗ and D⃗ have magnitudes of 3 units and 4 units, respectively. What is the angle between the directions of C⃗ and D⃗ if C⃗ · D⃗ equals:
(i) 0
(ii) 12 units
(iii) −12 units
Q. No. 3.
(a) Distinguish between linear and angular momentum. Explain the law of conservation of angular momentum.
(b) Estimate the net force needed to accelerate:
(i) A 1000 kg car at ½g.
(ii) A 200 g apple at the same rate.
(c) A vertical force is applied to a block of mass m resting on a floor. What happens to the magnitude of the normal force on the block from the floor as the applied force F is increased from zero if the force is:
(i) Downward
(ii) Upward
Q. No. 4.
(a) Describe the Michelson–Morley Experiment and explain how the negative result obtained from this experiment was interpreted.
(b) Derive the Lorentz velocity transformation equations and show that the speed of light is independent of the relative motion between the frames of reference.
Q. No. 5.
(a) What is surface tension? Explain how surface tension is responsible for the rise of liquid in capillary tubes.
(b) Water circulates throughout a house in a hot-water heating system. If the water is pumped at a speed of 0.50 m/s through a 4.0 cm diameter pipe in the basement under a pressure of 3.0 atm, what will be the flow speed and pressure in a 2.6 cm diameter pipe on the second floor, 5.0 m above? Assume that the pipes do not divide into branches.
(c) When blood pressure is measured, why must the cuff be held at the level of the heart?
Q. No. 6.
(a) What is polarization of waves? How can plane-polarized light be obtained by using a polarizing sheet?
(b) Two flat mirrors are perpendicular to each other. An incoming beam of light makes an angle of 15° with the first mirror. What angle will the outgoing beam make with the second mirror?
(c) Since the density of air decreases with an increase in temperature, but the bulk modulus (B) is nearly independent of temperature, how would you expect the speed of sound waves in air to vary with temperature?
Q. No. 7.
(a) State and explain the Equipartition Theorem.
(b) Define the laws of thermodynamics. Explain the Third Law of Thermodynamics in detail.
Q. No. 8.
Write short notes on any TWO of the following:
(a) Gyroscope
(b) Classical Maxwell–Boltzmann Statistics
(c) Spin and Precession
PAPER-II (Subjective) 80 Marks
PART-II
Attempt ONLY FOUR questions from PART-II, ALL Questions carry EQUAL marks.
Q. No. 2.
(a) Derive an expression for the torque and potential energy of an electric dipole in an electric field. (10)
(b) Show that the energy density of a parallel plate capacitor with dielectric medium between them is directly proportional to the square of electric field intensity. (6)
(c) In a microwave oven, torque acting on an electric dipole is responsible for the production of heat. Comment. (4) (20)
Q. No. 3.
(a) Discuss the origin of magnetism by considering the processes that create a magnetic field in an atom. (8)
(b) What are ferromagnetic domains? How is a typical ferromagnetic material investigated by the hysteresis loop for technological applications? (8)
(c) How does the effect of nuclear magnetism become important in Nuclear Magnetic Resonance (NMR)? (4) (20)
Q. No. 4.
(a) Derive an expression for the time-independent Schrödinger Wave Equation in one dimension for a single particle. Define the Hamiltonian operator. (10)
(b) Discuss the various quantum numbers used to describe the complete behavior of an electron in an orbital. (6)
(c) How slowly must an electron be moving for its de Broglie wavelength to be equal to 1 mm? (4) (20)
Q. No. 5.
(a) Discuss the behavior of a particle trapped in an infinitely deep potential well and show that the energy of the particle inside the well is quantized. (10)
(b) Explain the terms wave function, probability density and normalization condition associated with quantum mechanics. (6)
(c) Find the expectation value of the momentum. (4) (20)
Q. No. 6.
(a) What is an oscillator? How does an LC oscillator work? Discuss the Barkhausen criterion for oscillations. (10)
(b) What is feedback in a transistor? Differentiate between negative feedback and positive feedback. (6)
(c) What are RC filters? (4) (20)
Q. No. 7.
(a) Discuss the principle, construction and working of a Nuclear Reactor. Define a Breeder Reactor. (8)
(b) What is nuclear fusion? Describe the Proton-Proton cycle for energy release in the Sun and stars. (8)
(c) What is the Q-value of a nuclear reaction? (4) (20)
Q. No. 8.
Write comprehensive notes on any TWO of the following: (10 each)
(a) The Biot-Savart Law
(b) Cyclotron
(c) Electromagnetic Waves
(20)
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