PHYSICS, PAPER-II
FEDERAL PUBLIC SERVICE COMMISSION
COMPETITIVE EXAMINATION FOR
RECRUITMENT TO POSTS IN BPS-17 UNDER
THE FEDERAL GOVERNMENT, 2009
PHYSICS, PAPER-II
TIME ALLOWED: (PART-I) 30 MINUTES MAXIMUM MARKS:20
(PART-II) 2 HOURS & 30 MINUTES MAXIMUM MARKS:80
PART – I (MCQ)
(COMPULSORY)
Q.1. Select the best option/answer and fill in the appropriate box on the Answer Sheet. (20)
(i) The impedance of RLC series resonance circuit at resonant frequency is:
(a) Greater than R (b) Equal to R (c) Zero (d) None of these
(ii) An electron has a velocity of 10km/s normal to a magnetic field of 0.1 T flux density. If the radius
of the path is 569nm then the frequency is:
(a) 2.79 GHz (b) 3.1 MHz (c) 2.8 KHz (d) None of these
(iii) If a current of 10 A flows through an electric heater for an hour and converts 8.64 MJ of electrical
energy into heat energy. Then the potential difference across the heater is:
(a) 864 V (b) 240 V (c) 100 V (d) None of these
(iv) An alpha particle is accelerated to a velocity v in a particle accelerator by a potential difference of
1200 V. Which of the following potential differences would be needed to double the velocity of
the alpha particle?
(a) 2400 V (b) 3600 V (c) 4800 V (d) None of these
(v) Two thin parallel wires carry currents along the same direction. The force experienced by one due
to the other is:
(a) Parallel to the lines (b) perpendicular to the lines and attractive
(c) perpendicular to the lines and repulsive (d) None of these
(vi) If 300 mA current is passing through an electric bulb, then the number of electrons passing
through in one minute will be:
(a) 1.12×1020 (b) 1.6×1019 (c) 6.02×1018 (d) None of these
(vii) An electric iron of resistance 20 Ω takes a current of 5.0 A. The thermal energy developed in 30s
is:
(a) 15 kJ (b) 100 J (c) 10 J (d) None of these
(viii) An ideal gas has a volume of exactly 1 liter at 1.00 atm and –20°C. To how many atmospheres
pressure must it be subjected to be compressed to 0.500 liter at 40°C?
(a) 5.2 atm (b) 2.47 atm (c) 1.5 atm (d) None of these
(ix) In Bohr’s model the lowest orbit corresponds to:
(a) Maximum energy (b) Minimum energy (c) Zero energy (d) None of these
(x) The diffusion of the free electrons across the unbiased p-n junction produces:
(a) Forward bias (b) Reverse bias (c) Depletion region (d) None of these
(xi) The P-N junction, on forward biasing acts like a:
(a) Capacitor (b) Inductor (c) Insulator (d) None of these
(xii) The impedance at the resonant frequency of a series RLC circuits with L = 15 mH, C=0.015 F,
and R = 80 Ω:
(a) 0 KΩ (b) 30 Ω (c) 80 Ω (d) None of these
(xiii) Weber is a unit of:
(a) Magnetic field intensity (b) Magnetic Flux
(c) Magnetic Flux Density (d) None of these
(xiv) The magnetic flux through an element of area A in a uniform magnetic field B is expressed as:
(a) AB (b) B. A (c) A x B (d) None of these
(xv) In an electric circuit, currents flowing towards a node having four branches are 2A, -3A and 4A,
then the current in the fourth branch is:
(a) 2A (b) -3 A (c) 4 A (d) None of these
NOTE: (i) First attempt PART-I (MCQ) on separate Answer Sheet which shall be taken back
after 30 minutes.
(ii) Overwriting/cutting of the options/answers will not be given credit.
(iii) Use of Scientific Calculator is allowed.
S.No.
R.No.
PHYSICS, PAPER-II
(xvi) With the passage of time, the rate of decay of a radioactive element will:
(a) Increase exponentially (b) Decrease linearly
(c) Becomes zero in two half-life time (d) None of these
(xvii) The place where controlled fission chain reaction is carried is?
(a) A black hole (b) A star (c) A reactor (d) None of these
(xviii) In 19th century, Faraday and Maxwell worked on the unification of two forces named as:
(a) Gravitational and Weak forces (b) Electric and magnetic forces
(c) Weak and Strong forces (d) None of these
(xix) Electromagnetic wave theory of light was proposed by:
(a) Newton
(xx) The concept of field theory was put forward by:
(a) Franklin
PART – II
NOTE:
(i) PART-II is to be attempted on the separate Answer Book.
(ii) Attempt ONLY FOUR questions from PART-II. All questions carry EQUAL marks.
(iii) Extra attempt of any question or any part of the attempted question will not be
considered.
(iv) Use of Scientific calculator is allowed.
Q.2. (a) State and prove Gauss law. Compare it with Coulomb’s law for calculating electric field.
(4+4+2)
(b) Determine the E field caused by a spherical cloud of electrons with a volume charge density
= for 0 ≤ R ≤ b 0 ρ ρ (both ρ0 and b are positive) and ρ = 0 for R > b. Sketch the charge
distribution and electric field for this charge. (6+4)
Q.3. (a) Explain Maxwell’s equations. Write the fundamental relations for electrostatic and
magnetostatic models. How these were modified to Maxwell’s equations? What is the main
contribution of Maxwell in this regard? (4+2+4+2)
(b) Derive Maxwell’s two divergence equations from its two curl equations and the equation of
continuity. (4+4)
Q.4. (a) What are P-type and N-type semiconductors? Draw ampere-volt characteristic of a PN junction.
Why there is sudden increase in the small reverse saturation current at the breakdown voltage?
Write the uses of zener diode. (4+2+4+2)
(b) What are transistors? Draw the three common transistor circuits. Explain the function of
transistor in the saturation mode. (2+2+4)
Q.5. What is Compton Effect? Derive an expression for Compton
angle? What do you mean by Red Shift? (2+8+6+4)
Q.6. (a) Describe Schrodinger’s wave equation. Normalize Ψ = Ae−αx , where A andα are real
constants, A has units of (length)-1/2 andα with units of (length)-2. (6+4)
(b) What is the probability of finding the particle described by this wave function between x = 0.99
and x = 1.01 units? Also find the possible solution for E andV.
[Given the integration from -∝ to +∝ ( / 2) 2 ∫ = π − dx x
e
] (4+6)
Q.7. (a) Explain Radioactive decay. Find an expression for decay rate. Relate half life to the
disintegration constant. What are the units for the measurement of radioactivity? (4+6+2+2)
(b) A 2.71g sample of radioactive KCI is decaying at a constant rate of 440 Bq into the isotope 40K,
which constitutes 1.17% of the normal potassium. Calculate the half-life of this nuclide. (6)
Q.8. Write short notes on ANY TWO of the followings: (10,10)
(i) Poynting theorem and Poynting vectors
(ii) Elementary particles and their properties
(iii) Unification of forces.
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