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) Describe Einstein’s postulates of the Special Theory of Relativity. Differentiate between the Special Theory of Relativity and the General Theory of Relativity.
(b) Establish the mass-energy relationship and explain its significance.
Q. No. 3.
(a) Differentiate between Fermi-Dirac, Bose-Einstein and Maxwell-Boltzmann statistics. Give one application of each.
(b) Draw a labelled diagram of a nuclear reactor and explain the significance of each part.
Q. No. 4.
(a) Distinguish between linear momentum and angular momentum. Express Newton’s Second Law in terms of linear motion and angular motion.
(b) Discuss the acceptor and rejecter electronic circuits.
Q. No. 5.
(a) Describe and explain Miller indices. Explain the symbols:
<111>
[010]
(111)
(b) Discuss the closest-packed crystal structures.
Q. No. 6.
(a) Can you imagine a three-dimensional diffraction grating? Describe it in detail.
(b) Justify the dual nature of light with suitable examples.
Q. No. 7.
(a) State and explain the three laws of Thermodynamics.
(b) What is a heat engine? Determine the efficiency of an engine if it absorbs 10,000 J of heat and delivers 2000 J of work per cycle.
Q. No. 8.
Write notes on any TWO of the following:
(a) Michelson–Morley experiment and its latest application in a recent Nobel Prize.
(b) Unification of forces and the contribution of Abdus Salam.
(c) An essay on the Large Hadron Particle Accelerator.
PAPER-II (Subjective) 80 Marks
PART-II
Attempt ONLY FOUR questions from PART-II, ALL Questions carry EQUAL marks.
Q. No. 2.
(a) Consider an infinitely long cylindrical insulating shell of inner radius a and outer radius b having a uniform volume charge density ρ. If a line of charge density λ is placed along the axis of the shell, determine the electric field intensity at a point r such that:
(i) a < r < b
(ii) r > b (8)
(b) Determine the energy density for a capacitor. (6)
(c) Discuss the Lorentz force. (6) (20)
Q. No. 3.
(a) Find the magnetic energy density for the magnetic field of an inductor. (10)
(b) State and explain Lenz’s Law. (6)
(c) Why is the work done by a magnetic field on a charged particle always zero? (4) (20)
Q. No. 4.
(a) Describe the properties of an electron and light that show their dual nature. (8)
(b) State and explain the de Broglie hypothesis. (6)
(c) Metals A, B and C have work functions 2.2 eV, 3.6 eV and 4.8 eV, respectively. If light of wavelength 320 nm is incident on these metals, find:
(i) Which metals exhibit the photoelectric effect?
(ii) The maximum kinetic energy of the photoelectrons in each case. (6) (20)
Q. No. 5.
(a) Determine the transmission coefficient for a particle having energy E incident on a rectangular barrier, where E < V₀. The barrier is given by:
V(x) = {
V₀, for −a < x < a
0, for |x| > a
} (10)
(b) For an operator Â, we know [Ĥ, Â] = 0, where Ĥ is the Hamiltonian operator. What can we conclude about the eigenstates of  and the expectation value ⟨Â⟩? (6)
(c) Give two examples of the operator  mentioned in part (b). (4) (20)
Q. No. 6.
(a) Describe the electrical conduction in different types of solids in terms of Band Theory. (8)
(b) Explain the crystal structure of diamond. (6)
(c) Find the carrier concentration of electrons in silicon at a temperature of 25°C. (6) (20)
Q. No. 7.
(a) What factors contribute to the stability of a nucleus? Draw and explain the plot of neutron number (N) versus atomic number (Z) for stable nuclei. (10)
(b) Explain the use of chain reaction in relation to a nuclear reactor. (6)
(c) The stable isotope of potassium is ¹⁹K. What kind of radioactivity do you expect from ¹⁸K? Give reasons. (4) (20)
Q. No. 8.
Write notes on any TWO of the following: (10 marks each)
(a) Poynting Vector
(b) Fusion in Stars
(c) MOSFET
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