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 (Objective) 20 Marks
PART-I
Q.1.
(i) Select the best option/answer and fill in the appropriate Circle on the OMR Answer Sheet. (20×1=20)
(ii) Answers given anywhere other than the OMR Answer Sheet shall not be considered.
1. The square of the orbital period of a planet is:
(a) Directly proportional to the cube of the semi-major axis of its orbit.
(b) Directly proportional to the cube of the semi-minor axis of its orbit.
(c) Inversely proportional to the cube of the semi-major axis of its orbit.
(d) Inversely proportional to the cube of the semi-minor axis of its orbit.
(e) None of these
2. If the velocity of a particle becomes doubled, then its K.E.:
(a) Becomes doubled
(b) Reduces to half
(c) Becomes four times
(d) None of these
3. The P.E. of a simple harmonic oscillator is:
(a) −½kx²
(b) ½kx²
(c) kx²
(d) kx
(e) None of these
4. Two car racers are 100 km away from each other. They drive their cars at 40 km/h and 60 km/h respectively towards each other. After 15 minutes they will be at a distance of:
(a) 25 km
(b) 50 km
(c) 60 km
(d) 75 km
(e) None of these
5. The equation of adiabatic change is:
(a) PVᵞ = K
(b) PᵞV = K
(c) (PV)ᵞ = K
(d) None of these
6. By exerting a certain amount of pressure on an ice block, you:
(a) Raise its melting point
(b) Lower its melting point
(c) Make it melt at 0°C only
(d) None of these
7. Mercury thermometer can be used to measure temperature up to:
(a) 250°C
(b) 100°C
(c) 360°C
(d) 500°C
(e) None of these
8. Three vectors A, B and C, not in the same plane, make a parallelepiped. The volume of the parallelepiped is:
(a) (A × B) × C
(b) (A · B) × C
(c) (A × B) · C
(d) A · B · C
(e) None of these
9. The moment arm (r = 4 m) and force (F = 10 N) make an angle of 30° about the turning point. The torque produced will be:
(a) 40 N·m
(b) 20 N·m
(c) 34.6 N·m
(d) None of these
10. In total internal reflection, the refracted ray makes an angle of ______ with the normal.
(a) 0°
(b) 90°
(c) 180°
(d) None of these
11. Solar eclipse occurs when:
(a) Earth is between the Sun and the Moon
(b) Sun is between the Moon and the Earth
(c) Moon is between the Earth and the Sun
(d) None of these
12. Light is dispersed into different colours when passing through a glass prism because:
(a) Refraction of light occurs in glass
(b) Refractive index of different colours is different
(c) Glass is denser than air
(d) None of these
13. A ball is thrown with a velocity of 8ĵ m/s. The acceleration is (4î + 2ĵ) m/s², where î and ĵ are unit vectors. The displacement after 5 seconds is:
(a) 52 m
(b) 68 m
(c) 82 m
(d) None of these
14. The time period of a second’s pendulum is 2 s. The mass of the spherical bob is 50 g and it is hollow. If it is replaced by another solid bob of the same radius but mass 100 g, then its time period will be:
(a) 8 s
(b) 4 s
(c) 1 s
(d) 2 s
(e) None of these
15. The equation of displacement of a harmonic oscillator is:
x = 3 sinωt + 4 cosωt (m)
The amplitude of the particle will be:
(a) 1 m
(b) 5 m
(c) 7 m
(d) 12 m
(e) None of these
16. One m³ is equivalent to:
(a) 1000 litres
(b) 100 litres
(c) 10 litres
(d) None of these
17. The frequency of a second’s pendulum is:
(a) 2 Hz
(b) 1 Hz
(c) 0.5 Hz
(d) None of these
18. The gradient of scalar potential is:
(a) Scalar quantity
(b) Vector quantity
(c) Neither scalar nor vector
(d) None of these
19. Beats are produced because of:
(a) Interference of sound waves
(b) Refraction of sound waves
(c) Diffraction of sound waves
(d) None of these
20. Sound waves are:
(a) Longitudinal
(b) Transverse
(c) Electromagnetic
(d) None of these
PAPER-I (Subjective) 80 Marks
PART-II
Attempt ONLY FOUR questions from PART-II, ALL Questions carry EQUAL marks.
NOTE:
(i) Part-II is to be attempted on the separate Answer Book.
(ii) Candidate must write the Question No. in the Answer Book according to the Question Paper.
(iii) Attempt ONLY FOUR questions from Part-II. ALL questions carry EQUAL marks.
(iv) Extra attempt of any question or any part of the attempted question will not be considered.
(v) Use of Calculator is allowed.
Q.2.
(a) The vectors
A = 2î + ĵ + 3k̂
B = î − 2ĵ − k̂
Find:
(i) |A|
(ii) |B|
(iii) A · B
(iv) Projection of B on A. (2,2,3,3)
(b) Prove that:
A × (B × C) = B(A · C) − C(A · B). (6)
(c) Are the unit vectors in cylindrical and spherical coordinate systems constant vectors? Explain. (4)
Q.3.
(a) State Kepler’s laws of planetary motion and prove:
(i) Law of Areas
(ii) Law of Periods (2,4,4)
(b) Use Maxwell’s equations to derive the electromagnetic wave equation. (10)
Q.4.
(a) What is Doppler Effect? Derive expressions for the frequency of sound heard by an observer when:
(i) The observer is moving towards a stationary source.
(ii) The source is moving towards a stationary observer. (2,6,6)
(b) A stationary observer detects sound of frequency 250 Hz emitted from a source at rest. He detects a frequency of 750 Hz when the source is moving towards him with constant velocity. Determine the velocity of the source.
(Velocity of sound = 341 m/s) (6)
Q.5.
(a) Describe Young’s Double Slit Experiment and derive the conditions for constructive and destructive interference. (10)
(b) A double slit arrangement is illuminated by light of wavelength 546 nm. The slits are 0.12 mm apart and the screen is 55 cm away.
Find:
(i) The angular position of the first maximum.
(ii) The linear distance between the 3rd and 4th maxima. (4,6)
Q.6.
(a) Describe the postulates of Special Theory of Relativity. Show the relativistic effects on mass, length and time. (3,3,3,3)
(b) What is the total energy E of a 2.53 MeV electron? (When an energy is used as an adjective, it refers to the kinetic energy of the particle; here K = 2.53 MeV.) (8)
Q.7.
(a) Derive the expressions for position and time coordinates in frame S′ relative to frame S (Lorentz Transformation). (12)
(b) Derive Bernoulli’s equation for steady flow. (8)
Q.8. Write short notes on ANY TWO of the following:
(a) Travelling and Standing Waves
(b) LASER, its production and applications
(c) Laws of Thermodynamics
PAPER-II (Objective) 20 Marks
PART-I
Q.1. (i) Select the best option/answer and fill in the appropriate Circle on the OMR Answer Sheet. (20 × 1 = 20)
(ii) Answers given anywhere, other than OMR Answer Sheet, shall not be considered.
1. If whole charge is concentrated at a point then the volume charge density outside the point is:
(a) 1
(b) Zero
(c) Infinity
(d) None of these
2. Potential due to point charge is:
(a) Symmetric
(b) Anti-symmetric
(c) Radially symmetric
(d) Spherically symmetric
(e) None of these
3. Pointing Vector represents:
(a) Current
(b) Current density
(c) Energy flux
(d) Magnetic induction
(e) None of these
4. Boundary conditions are used for solution of:
(a) Homogenous Equation
(b) Inhomogeneous Equation
(c) Both of these
(d) None of these
5. The direction of the induced e.m.f. is given by:
(a) The induced e.m.f. rule
(b) The Cockscrew rule
(c) Ampere’s swimming rule
(d) Fleming’s right-hand rule
(e) None of these
6. How many valence electrons are in every semiconductor material?
(a) 1
(b) 2
(c) 3
(d) 4
(e) None of these
7. Minority carriers are many times activated by:
(a) Heat
(b) Pressure
(c) Dopants
(d) None of these
8. If conductance increases as temperature increases, this is known as a:
(a) Positive coefficient
(b) Negative current flow
(c) Negative coefficient
(d) Positive resistance
(e) None of these
9. Three different points are shown on a DC load line. The upper point represents the:
(a) Minimum current gain
(b) Quiescent point
(c) Saturation point
(d) Cutoff point
(e) None of these
10. The Solid-State Detector is basically:
(a) A forward biased p-n junction
(b) A reverse biased p-n junction
(c) A forward biased transistor
(d) A photocell
(e) None of these
11. The signal voltage gain of an amplifier (Av) is defined as:
(a) Av = Vin / Vout
(b) Av = Ic × Rc
(c) Av = Rc / RE
(d) Av = Rc / RL
(e) None of these
12. The total number of electrons around the nucleus is called:
(a) Atomic number
(b) Mass number
(c) Avogadro’s number
(d) Gram mole
(e) None of these
13. Nuclei of the same element having the same Z but different values of N are called:
(a) Isotopes
(b) Isobars
(c) Isomers
(d) Allotropes
(e) None of these
14. Charge on each α-particle is equal to:
(a) The charge on proton
(b) Twice the charge on proton
(c) Three times the charge on proton
(d) Four times the charge on proton
(e) None of these
15. Which of the following particles move with the velocity of light?
(a) α-particle
(b) β-particle
(c) γ-particle
(d) None of these
16. How many neutrons are in the nuclide ⁶⁶Zn?
(a) 66
(b) 36
(c) 30
(d) 26
(e) None of these
17. Which particle is considered as an ideal projectile for induced nuclear reactions?
(a) Electron
(b) Proton
(c) Neutron
(d) γ-particle
(e) None of these
18. The function of the moderator in a nuclear reactor is:
(a) To slow down the neutrons
(b) To absorb the neutrons
(c) To cool the reactor
(d) To control the energy released
(e) None of these
19. Which of the following process is responsible for energy emission in the Sun?
(a) Alpha decay
(b) Beta decay
(c) Fission
(d) Fusion
(e) None of these
20. The half-life of a radioactive substance is 10 days. This means that:
(a) Completely disintegrates in 20 days
(b) Completely disintegrates in 40 days
(c) 1/8 will be left after 40 days
(d) 7/8 part disintegrates in 30 days
(e) None of these
PAPER-II (Subjective) 80 Marks
PART-II
Attempt ONLY FOUR questions from PART-II, ALL Questions carry EQUAL marks.
Q.2.
(a) State and explain Gauss’s Law in Electrostatics and express it in differential form. (10)
(b) Find the electric intensity at a point outside a volume distribution of charge confined in a region of radius R. (10)
Q.3.
(a) State and explain Faraday’s Law of Electromagnetic Induction. (10)
(b) How are Maxwell’s equations derived from the fundamental relations for electrostatic and magnetostatic models? Explain these equations. (10)
Q.4.
(a) Explain P-N junction as a rectifier. (6)
(b) How is a transistor formed? Give the construction and symbol of a PNP transistor. (8)
(c) How does the resistivity of semiconductors change with temperature? (6)
Q.5.
(a) Explain Compton Effect and Photoelectric Effect. How do they support the photon theory of light? (10)
(b) Discuss De-Broglie’s Hypothesis. (10)
Q.6.
(a) Discuss Bohr’s atomic model and its success. How does Rutherford’s orbital motion violate classical physics? (10)
(b) Describe Schrödinger’s wave equation. (10)
Q.7.
(a) What is radioactive decay? Define half-life and average life and relate half-life to the disintegration constant. (10)
(b) Discuss elementary particles and their properties. (10)
Q.8.
Write notes on ANY TWO of the following: (10 each)
(a) Poynting Theorem and Poynting Vector
(b) Nuclear Fission and Fusion
(c) Band Theory of Solids
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