PHYSICS, PAPER-II
FEDERAL PUBLIC SERVICE COMMISSION
COMPETITIVE EXAMINATION FOR
RECRUITMENT TO POSTS IN BPS-17 UNDER
THE FEDERAL GOVERNMENT, 2010
PHYSICS, PAPER-II
(PART-I) 30 MINUTES MAXIMUM MARKS:20
TIME ALLOWED:
(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) A Watt – sec is a unit of:
(a) Force (b) Energy (c) Power (d) None of these
(ii) The direction of any magnetic induction effect is such as to oppose the cause of the effect. This is:
(a) Coulumb's Law (b) Ampere's Law (c) Lenz's Law (d) None of these
(iii) A magnetic field cannot:
(a) accelerate a charge (b) Exert a force on a charge
(c) change the kinetic energy of a charge (d) None of these
(iv) The inverse of resistivity is called Conductivity. Its unit is:
(a) Ohm-1 (b) ohm-metre (c) (ohm-meter)-1 (d) None of these
(v) An LRC Circuit has R= 4Ω, Xc = 3 and XL=6, the impedence of the circuit is:
(a) 5 Ω (b) 7 Ω (c) 13 Ω (d) None of these
(vi) A "step-down" transformer is used to:
(a) increase the power (b) decrease the voltage (c) Increase the voltage (d) None of these
(vii) Electrical potential is the potential energy per unit:
(a) Charge (b) Voltage (c) Force (d) None of these
(viii) The force on a charge moving with the velocity in a magnetic field B is given by:
(a) F = (q/v x B) (b) F = ( qv x B ) (c) F = (qv + B) (d) None of these
(ix) A changing current "i" in any circuit induces an emf "e" in that circuit, which is equal to:
(a) e = di/dt (b) E = i dΦ/dt (c) e = - L di/dt (d) None of these
(x) Inductive reactance of an inductor is:
(a) XL= ω2L (b) XL = ω/L (c) e = -L di/dt (d) None of these
(xi) The resonant frequency of an LC-Circuit is:
(a) f = 2Π LC (b) f = 1 / 2Π√ LC (c) f = 1/ 2LC (d) None of these
(xii) The deliberate addition of an impurity element in a semi-conductor is called:
(a) doping (b) annealing (c) mixing (d) None of these
(xiii) The conversion of AC into DC is called:
(a) amplification (b) rectification (c) modulation (d) None of these
(xiv) The Laser light is:
(a) monochromatic (b) coloured (c) chromatic (d) None of these
(xv) The Laser light may be obtained from:
(a) quartz crystal (b) NaCl crystal (c) ruby crystal (d) None of these
(xvi) The emission of photoelectrons in photoelectric effect is dependent on:
(a) threshold frequency (b) intensity of light (c) Nature of metal (d) None of these
(xvii) Which one of the following is NOT needed in Nuclear Fission reactor:
(a) fuel (b) accelerator (c) moderator (d) None of these
(xviii) The half life of a radioactive isotope is 140 days. How many days would it take to loose 3/4 of its
initial activities:
(a) 105 days (b) 280 days (c) 35 days (d) None of these
(xix) Most of the energy produced in Sun is due to:
(a) Nuclear fusion (b) Chemical reaction (c) Nuclear Fission (d) None of these
(xx) A U-235 nucleus will split when it captures:
(a) an α-particle (b) e.m. radiation (c) neutron (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.
Roll Number
PHYSICS, PAPER-II
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's Law in electrostatics and express the law in differential
forms. (14)
(b) Find the electric intensity at a point outside a volume distribution of charge confined into a
spherical region of radius R. (06)
Q.3. (a) State and explain Ampere's Law. Derive an expression for the value of 'B' inside a solenoid.
(14)
(b) A thin 10 cms long solenoid has a total of 400 turns of wire and carries a current of 0.20 amp.
Calculate the field inside near the centre.
(06)
Q.4. (a) How a Semi Conductor diode is used as a half wave and full wave rectifier? (08)
(b) What are the transistors? Give Construction and Symbol of PNP and NPN transistor. (07)
(c) The resistivity of a metal increases with increase in temperature while that of a semi conductor
decreases. Explain. (05)
Q.5. (a) Discuss briefly the wave nature of matter and obtain an expression of de Broglie's wavelength
for matter waves. (14)
(b) Calculate the de Broglie's wavelength of a 0.20kg ball moving with a speed of 15 m/s. (06)
Q.6. (a) Derive Einstein's photoelectric effect on the basis of quantum theory and derive Einstein's
photoelectric equations. (14)
(b) Calculate the work function of Na in electron-volts, given that the threshold wavelength is 6800
A° and h = 6.625 x 10-34 J-S (06)
Q.7. (a) Define the terms decay constant, half life and average life as applied to a radioactive substance.
Find the relation between them. (11)
(b) The half life of Radium is 1590 years. In how many years will one gm of pure element (a)loose
one centigram and (b)be reduced to one centigram. (07)
(c) When a nucleus emits a γ – ray photon, what happens to its atomic number and its actual
mass. (02)
Q.8. Write notes on ANY TWO of the following: (20)
(a) Self and Mutual Inductance
(b) Pauli's Exclusion Principle
(c) Compton
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