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FEDERAL PUBLIC SERVICE COMMISSION
COMPETITIVE EXAMINATION FOR RECRUITMENT TO POSTS
IN B.P.S. – 17, UNDER THE FEDERAL GOVERNMENT, 2002

Time Allowed: 3 hours
Maximum Marks: 100

PAPER II

Note: Attempt FIVE questions in all, including Question No. 8, which is compulsory. All questions carry equal marks.

Q.1 (a) Extend Gauss’s theorem to derive poisson’s equations. Show that Laplace’s equations are Poisson’s equation s written in an other way.
Consider an isolated uniformly charged spherical conductor. Calculate the Electric intensity at points (i) outside and (ii) inside the sphere.

Q.2 (a) What is a Poynting vector? Evaluate it for an electromagnetic wave.
Calculate the flow of electromagnetic energy into a resistor-cylindrical of length ‘L’, radius ‘r’ and resistance across which a potential difference ‘V’ is applied.

Q.3 (a) Describe triode value and discuss its static and dynamic characteristics.
(b) Howa triode value can be used as an amplifier?
(c) A triode value has a mutual conductance of 2.5 ma per volt and an anode ac resistance of 20,000 ohms. Find the load resistance which must b inserted in the anode circuit to obtain a stage gain of 30.

Q.4 (a) Describe a PN junction. Discuss its ampere-volt characteristics. Why there is sudden increase in the small reverse saturation current at the Breakdown voltage? Write the uses of Zener diode.
(b) What are transistors? Draw the 3 types of ten common resistors circuits. Define de alpha and de beta of a transistor.

Q.5 (a) Describe Compton effect and find out the expression for the change in wavelength when an electromagnetic photon strikes a particle – an electron of an atom.
(b) How much is the maximum change in wavelength in terms of Compton wavelength?
(c) An X-ray photon whose initial frequency was 05 1.5×(10)^19 Hz emerges from a collision with an electron, with a frequency of 1.2×(10)^19 Hz. How much kinetic energy imported to the electron?

Q.6 (a) What is nuclear fission, fission cross-sections and thresholds? Describe a nuclear reactor.
(b) When an atom of ^( 235) U undergoes fission in a Statement reactor, about 200 Mev energy is liberated. Suppose that a reactor using uranium-235 has an output of 700 MW and is 20% efficient:
(i) How many atoms does it consume in one day?
(ii) What mass of uranium does it consume daily?

Q.7 Write short essay on any TWO of the following:
a. Integrated Circuits (ICs) and their role in the advancement of present technologies.
b. Isotopes and the uses of radio isotopes.
c. Nature of and the experiments which confirm duality behaviour.

Q.8 Write only the correct answer in the Answer Book. Don’t reproduce the questions.

1. Which of the following deals with the properties of matter and energy and their mutual relationship?
a. Chemistry
b. Astronomy
c. Physics
d. None of these

2. The mass of electron is:
a. 1.9 x 10-31 Kg
b. 9.1 I x 10-28 g
c. Equal to proton
d. None of these

3. The radius of hydrogen atom is:
a. 5.3 x 10 - 10 m
b. .53 x 10-10 m
c. .053 x 10-10 m
d. None of these

4. The radioactive substance whose half life is 7 days, decays completely in:
a. 14 days
b. 21 days
c. 28 days
d. None of these

5. The spiltting of spectral lines of an element when it radiates is a magnetic field is known as:
a. Induced emission
b. Zeaman effect
c. Population inverse
d. None of these

6. Normally the emitter of a transistor is:
a. Reverse biased
b. Forward biased
c. Not biased
d. None of these

7. Fission chain reaction is controlled by introducing rods of:
a. Graphite
b. Cadmium
c. Boron
d. None of these

8. The first atomic reactor was introduced by:
a. Curie
b. Wilson
c. Rutherford
d. None of these

9. Gamma rays waves like:
a. Sound waves
b. Beta waves
c. X-rays
d. None of these

10. The path Beta particle is:
a. Straight
b. Circular
c. Zig-zag
d. None of these

11. Which one is most penetrating?
a. β-rays
b. X-rays
c. γ-rays
d. None of these

12. A forward biased diode has resistance:
a. Zero
b. Infinite
c. Equal to reverse biased one
d. None of these

13. The reverse current through a semiconductor is due to:
a. Majority carriers
b. Electrons
c. Minority carriers
d. None of these

14. The energy of radio waves is greater than:
a. Light
b. Microwaves
c. X-rays
d. None of these

15. Thermal neutrons are:
a. At high temperature
b. Fast moving
c. Slow moving
d. None of these

16. In Somatic radiation damage there is:
a. Loss of hearing
b. Loss of hearing loss of hair
c. Ultraviolet beams
d. None of these

17. Laser beam consists of:
a. Monochromatic light
b. White light
c. Ultraviolet light
d. None of these

18. Which one is independent of frequency:
a. Impedance
b. Reactance
c. Resistance
d. None of these

19. N-type material is electronically:
a. Negative
b. Positive
c. Neutral
d. None of these

20. The alternating current in the Secondary coil of a transformer is induced by:
a. A varying electric field
b. A varying magnetic field
c. dc in the primary coil
d. None of these
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P.R.
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