Physics Papers 2000
 

[CENTER][CENTER][B]FEDERAL PUBLIC SERVICE COMMISSION[/B][/CENTER]
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[CENTER][CENTER][B]COMPETITIVE EXAMINATION FOR RECRUITMENT TO POSTS[/B][/CENTER]
[/CENTER]
[CENTER][CENTER][B]IN BPS – 17 UNDER THE FEDERAL GOVERNMENT, 2000

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[CENTER][CENTER][U][B]PHYSICS PAPER - I

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[CENTER][CENTER][B][U]TIME ALLOWED: 3 HOURS MAXIMUM MARKS: 100[/U]

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

[/B] 1. (a) Find a unit vector which is perpendicular to the vectors î +j and j + ?. (5)
(b) If A = xz î – y2 j + 2x2y?ˆ and =x2yz2, find (15)

2. (a) Define angular momentum of a single particle and derive a relation between torque and angular momentum. (10)
(b) Calculate the angular momentum, about the Earth’s center of a 50 kg person on the equator of the rotating earth. (10)

3. Describe with the help of necessary diagrams the details of Michelson-Morley experiment. What was the conclusion drawn from the results of the experiment. (20)

4. (a) Write down Maxwell’s distribution function for molecular speeds in a gas. Give the details of various parameters involved. (10)
(b) A container filled with N molecules of Oxygen gas is maintained at 300 K. What fraction of the molecules has speeds in the range 599-601 m/see? The molar mass M of Oxygen is 0.032 kg/mole. (10)

5. Differentiate between Phase and Group velocities. Given that phase velocity V of waves in deep water is (g l /2p ) 1/2 ,find their group velocity v. (20)

6. What is interferometer? Describe the construction and working principle of an interferorneter with which you are familiar. (20)

7. Write short notes on the following;
(a) Viscosity
(b) Planetary Motion
(c) Laws of Thermodynamics and their importance in daily life. (20)

[CENTER][B][U] COMPULSORY QUESTION

[/U][/B][/CENTER]
[B] 8. Write only the correct answers in the answer book. Do not reproduce the questions.

[/B] 1) If the speed of particle is doubled then its kinetic energy becomes
(a) Doubled.
(b) Unchanged
(c) Four time.
(d) Half of the initial value

2) A ping - pong ball of mass m moving with velocity v bounces off a concrete surface with the same speed in the opposite direction. The change in it’s linear momentum is
(a) 2mw
(b) mv
(c) 1/2mv
(d) Zero

3) The work done by a force of 20 N in displacing an object through a distance of 5 cm is
(a) 100 J
(b) 4 J
(c) 400 J
(d) 1 J

4) The weight of an astronaut in space far from any planet in
(a) Zero
(b) Different than on earth
(c) Same on earth

5) A net force needed to give a mass of 250 kg an acceleration of 5 cm/sec2 is
(a) 25N
(b) 12.5N
(c) 10N
(d) 5N

6) A light year is a unit of
(a) Time
(b) Distance
(c) Velocity
(d) Intensity of light

7) A spaceship is circling a planet at a distance of 10000 km from its center. Assume that the radius of the planet is 5000 km mid the acceleration clue to gravity on it’s surface is 10 rn/sec2. The speed of the spaceship is
(a) 5 km/sec
(b) 1 km/sec
(c) 10km/sec
(d) 25 km/sec

8) A uniform spring with force constant K is cut into halves. Whet is the spring constant for one of the halves?
(a) Half of the original one.
(b) Twice the original one
(c) 1/4 of original one
(d) Same original one

9) A watt is the unit of
(a) Energy
(b) Power
(c) Work
(d) Capacity

10) Two bodies are in thermal equilibrium with each other if they have same
(a) Pressure
(b) Density
(c) Energy
(d) Temperature

11) The number of grams in one mole of Helium gas are
(a) 1gm/mole
(b) 4gm/mole
(c) 6 gm/mole
(d) 2 gm/mole

12) A gas consists of a mixture of He and N2 molecules The speed of He molecules Intl. mixture is
(a) Slower than N2 molecules
(b) Greeter than N2 molecules
(c) equal to N2 molecule.

13) If a gas is compressed constant temperature, then the mean free path of the molecules of the gas,
(a) decreases
(b) remain the same
(c) increases

14) The melting point of the element Sulfur is 113 °C. It’s temperature at Fahrenheit scale is
(a) 45 °F
(b) 113 °F
(c) 63 °F
(d) 8l °F

15) Diffraction of waves occurs because of
(a) medium change
(b) uncertainty principle
(c) geometry of the object obstructing the wave
(d) none of these

16) Beats in sound are a result of
(a) two sound waves with different speeds
(b) in-homogenous medium
(c) superposition of two waves with different frequencies
(d) the relative motion of one of the sound source.

17) Light of certain colour is composed of train of waves, each 0.250 m long. The number of waves in 1 meter distance are
(a) 2500000
(b) 5000000
(c) 4000000
(d) 250

18) Longitudinal waves do not exhibit
(a) refraction
(b) reflection
(c) diffraction
(d) polarization

19) If mass of a simple pendulum is doubled, it’s period
(a) remain unchanged
(b) doubled
(c) becomes half of the original
(d) None of these

20) Diagnostic ultrasound of frequency 4.50 MHz is used to examine tumors in soft tissue. If the speed of sound in tissue is 1500 m/sec. The wave length of this wave in tissue is
(a) 6750 mm
(b) 4.50 mm
(c) 1500 mm
(d) 333.3 mm

[CENTER][CENTER][B]FEDERAL PUBLIC SERVICE COMMISSION[/B][/CENTER]
[/CENTER]
[CENTER][CENTER][B]COMPETITIVE EXAMINATION FOR RECRUITMENT TO POSTS[/B][/CENTER]
[/CENTER]
[CENTER][CENTER][B]IN BPS – 17 UNDER THE FEDERAL GOVERNMENT, 2005.[/B][/CENTER]
[/CENTER]

[CENTER][CENTER][U][B] PHYSICS PAPER- II[/B][/U][/CENTER]
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[CENTER][CENTER][B][/B][/CENTER]
[/CENTER]
[CENTER][CENTER][B][U]TIME ALLOWED: THREE HOURS MAXIMUM MARKS:100[/U][/B][/CENTER]
[/CENTER]


[B] NOTE: Attempt FIVE questions in all, including question No.8 which is COMPULSORY. All questions carry equal marks.[/B]

Q.1. (a) A dielectric sphere is placed in a uniform electric field. Draw a neat diagram showing a distortion produced in the field. Calculate, electric field outside and inside the dielectric sphere. (10)
(b) Explain the dielectric polarization. Establish a relation between electric field strength E, polarization P and electric induction D. (10)

Q.2 (a) Give a brief account of the phenomenon of electromagnetic induction. Describe two experiments to demonstrate it. (10)
(b) Prove a relation between the induced e.m.f. and. the rate of change of lines of magnetic force through a circuit (10)

Q.3. (a) What is transistor biasing? How will you connect a PNP transistor in i) common base and ii) common emitter configurations. Draw their characteristics curves and discuss their current gain, voltage gain and input impedance. Give the applications of two configurations. (12)
(b) Deduce the conditions under which the discharge of a condenser is Oscillatory in character. Find an expression for the frequency of oscillations. (8)

Q.4. (a) Outline the basic facts of Photo electricity. Give the law of Photoelectric emission. How can they be explained? (12)
(b) The kinetic Energies of photoelectrons range from zero to 4.0x1019J, when light of wavelength 3000 A° falls on a surface, what is the stopping potential for this light? What is the threshold wavelength for the material? (8) (1 eV= 1.602x1O19J.)

Q.5. (a) State fundamental postulates of Bohr’s Theory of hydrogen atom Derive the mathematical expression for energy of electron in hydrogen atom. Give the interpretation of negative sign. (12)
(b) Give an account of different series of Spectral lines of hydrogen atom. (8)

Q.6. (a) Give the significance of Schrodinger’s Wave equation in wave mechanics. Apply it to calculate energies of particle in a box and discuss the results. (12)
(b) What is Ileisenberg’s Uncertainty principle? Explain its importance in the development of physics. (8)

Q.7. Write a short essay on any two of the following: (20)
(a) Nuclear Reactors and their classifications
(b) Mass Spectrometer and Isotope detection
(c) AM Radio Receivers and Transmitters


[CENTER][U][B]COMPULSORY QUESTION

[/B][/U][/CENTER]
[B] Q. 8. Write only the correct answer in the answer book. Don’t reproduce the questions: (20)

[/B] (1) The neutrino does not possess
(a) charge
(b) linear momentum
(c) angular momentum
(d) energy

(2) The particle whose properties are most nearly the same as those of the proton is the
(a) positron
(b) neutron
(c) antiproton
(d) positive ion
(e) none of these

(3) The element whose nuclei contain the most tightly bound nucleons is
(a) helium
(b) carbon
(c) iron
(d) uranium
(e) none of these

(4) As a sample of a radioactive nuclide decays, its half—life
(a) decreases
(b) remains the same
(c) increases
(d) any of the above, depending on the nuclide

(5) Current in an n-type semiconductor is carried by
(a) electrons
(b) holes
(c) positive ions
(d) electrolytes
(e) none of these

(6) Pauli’s exclusion principle states that no two electrons in an atom can
(a) be present in the same probability cloud
(b) have the same spin
(c) have, the same quantum numbers
(d) interact with each other
(e) none of these

(7) The number of possible orientations of an atomic electron in a magnetic field is
(a) 1
(b) 2
(c) 4
(d) 2p
(e) none of these

(8) A hydrogen atom is in its ground state when its orbital electron
(a) is within the nucleus
(b) has escaped from the atom
(c) is in its lowest energy level
(d) is stationary
(e) none of these

(9) Electromagnetic waves transport
(a) wavelength
(b) frequency
(c) charge
(d) energy
(e) all of these

(10) The reactance of a capacitor is proportional to
(a) Ö f
(b) f
(c) f2
(d) 1/f
(e) none of these

(11) The capacitive reactance of a 5-m F capacitor in a 20-kHz circuit is
(a) 0.63W
(b) 1.6W
(c) 5W
(d) 16W
(e) none of these

(12) The impedance of a circuit does not depend on
(a) I
(b) f
(c) R
(d) C
(e) all of these

(13) At resonance, itis not true that
(a) R=Z
(b) XL=1/XC
(c) P=IV
(d) I=V/R

(14) A voltmeter across an AC circuit reads 50 V and an ammeter in series with the circuit reads 5 A. The power consumption of the circuit
(a) is less than or equal to 250 W
(b) is exactly equal to 250 W
(c) is equal to or more than 250 W
(d) may be less than, equal to, or more than 250 W
(e) none of these

(15) The magnetic flux through a wire loop in a magnetic field B does not depend on
(a) the area of the loop
(b) the shape of the loop
(c) the angle between the plane of the loop and the direction of B
(d) the magnitude B of the field
(e) none of these

(16 The alternating current in the secondary coil of a transformer is induced by
(a) a varying electric field
(b) a varying magnetic field
(c) the iron core of the transformer
(d) motion of the primary coil
(e) none of these

(17) When a diamagnetic substance is inserted in a current carrying solenoid, the magnetic field is
(a) slightly decreased
(b) greatly decreased
(c) slightly increased
(d) greatly increased
(e) none of these

(18) The N-type semiconductor is electrically
(a) negative
(b) positive
(c) neutral
(d) charged

(19) When a 100¾ W, 240-V light bulb is operated at 200 V, the current that flows in it is
(a) 0.35 A
(b) 0.42 A
(c) 0.50 A
(d) 0.58 A
(e) none of these

(20) The a of a transistor is
(a) current gain in common base
(b) current gain in common emitter
(c) voltage gain in common emitter
(d) voltage gain in common base
(e) none of these

8. Write only the correct answers in the answer book. Do not reproduce the questions.

1) If the speed of particle is doubled then its kinetic energy becomes
(a) Doubled.
(b) Unchanged
[B](c) Four time.[/B]
(d) Half of the initial value

2) A ping - pong ball of mass m moving with velocity v bounces off a concrete surface with the same speed in the opposite direction. The change in it’s linear momentum is
[B](a) 2mw[/B]
(b) mv
(c) 1/2mv
(d) Zero

3) The work done by a force of 20 N in displacing an object through a distance of 5 cm is
[B](a) 100 J [/B]
(b) 4 J
(c) 400 J
(d) 1 J

4) The weight of an astronaut in space far from any planet in
[B](a) Zero[/B]
(b) Different than on earth
(c) Same on earth

5) A net force needed to give a mass of 250 kg an acceleration of 5 cm/sec2 is
(a) 25N
[B](b) 12.5N [/B]
(c) 10N
(d) 5N

6) A light year is a unit of
(a) Time
[B](b) Distance [/B]
(c) Velocity
(d) Intensity of light


8) A uniform spring with force constant K is cut into halves. Whet is the spring constant for one of the halves?
(a) Half of the original one.
(b) Twice the original one
[B](c) 1/4 of original one [/B]
(d) Same original one

9) A watt is the unit of
(a) Energy
[B](b) Power[/B]
(c) Work
(d) Capacity

10) Two bodies are in thermal equilibrium with each other if they have same
(a) Pressure
(b) Density
(c) Energy
[B](d) Temperature[/B]

11) The number of grams in one mole of Helium gas are
(a) 1gm/mole
[B](b) 4gm/mole[/B]
(c) 6 gm/mole
(d) 2 gm/mole


13) If a gas is compressed constant temperature, then the mean free path of the molecules of the gas,
[B](a) decreases[/B]
(b) remain the same
(c) increases

14) The melting point of the element Sulfur is 113 °C. It’s temperature at Fahrenheit scale is
(a) 45 °F
(b) 113 °F
(c) 63 °F
[B](d) 8l °F[/B]

15) Diffraction of waves occurs because of
[B](a) medium change [/B]
(b) uncertainty principle
(c) geometry of the object obstructing the wave
(d) none of these

16) Beats in sound are a result of
(a) two sound waves with different speeds
(b) in-homogenous medium
[B](c) superposition of two waves with different frequencies[/B]
(d) the relative motion of one of the sound source.


18) Longitudinal waves do not exhibit
(a) refraction
(b) reflection
(c) diffraction
[B](d) polarization[/B]

19) If mass of a simple pendulum is doubled, it’s period
(a) remain unchanged
(b) doubled
[B](c) becomes half of the original [/B]
(d) None of these

20) Diagnostic ultrasound of frequency 4.50 MHz is used to examine tumors in soft tissue. If the speed of sound in tissue is 1500 m/sec. The wave length of this wave in tissue is
(a) 6750 mm
(b) 4.50 mm
(c) 1500 mm
[B](d) 333.3 mm[/B]

(12) The impedance of a circuit does not depend on
[B](a) I [/B]
(b) f
(c) R
(d) C
(e) all of these

3) The work done by a force of 20 N in displacing an object through a distance of 5 cm is
[B](a) 100 J [/B]
(b) 4 J
(c) 400 J
(d) 1 J

Its 1 J option (d)
cm must be converted to meter first

14 number objective is doubtful. farenheit temperature must be more than celcius temperature. the answer is 235 F. according to F= 1.8 C+32