CSS Physics Past Paper 2025

Instructions specific to this paper

• First attempted Part-I (MCQS) on the separate OMR Answer Book which shall be taken back
• Overwriting/cutting of the options/answers will not be given credit.
• There is no negative marking. All MCQs must be attempted.
• Answers given anywhere else, other than OMR Answer Sheet, will not be considered.
• Attempt ONLY FOUR questions from PART-II. ALL questions carry EQUAL marks.

Questions

1. Q. 210 marks

   (a) State and prove Stoke's theorem. (b) Prove that if the vector is the gradient of a scalar function then its line (6) integral around a closed curve is zero. (c) A particle moves along the curve x = 2t², yt-4t, z3t-5 where t is (4) (20) the time. Find the components of its velocity and acceleration at time t=1 in the direction 2i-3j+2k

2. Q. 310 marks

   (a) Differentiate between Fermi-Dirac, Bose-Einstein and Maxwell- Boltzman's statistics. (b) What do you understand by classical statistical mechanics and quantum (6) statistical mechanics? (c) A 0.5m³ vessel is filled with air at atmospheric pressure. The air is (4) (20) churned by a paddel wheel attached to a shaft 0.1m in diameter, rotating at a speed of 1800 rpm. A force of 5.0N acts on the rim of the shaft. What would be the pressure in the vessel after 10 sec of operation?

3. Q. 410 marks

   (a) What is viscosity? Discuss effect of temperature on the viscosity of liquids and gases. (b) Explain why the level of mercury is down in capillary when placed in (6) container of mercury, while it is up in the capillary in case of water? (c) A garden hose has an an inside diameter of 2 cm and water flows through it is (4) (20) at 3 m/s. (i) What nozzle diameter is required for the water to emerge at 10 m/s? (ii) At what rate does the water leave the nozzle?

4. Q. 510 marks

   (a) Discuss analytical treatment of interference of light to calculate intensity in double slit interference. Describe the conditions of maximum and minimum intensity and also draw the intensity pattern for double slit interference. (b) What is resolving power of a grating? Show that it increases with the order (6) of image. (c) A body having SHM has an amplitude of 5cm, and a period of 0.2s. When (4) (20) the displacement is 5cm, find the acceleration and velocity.

5. Q. 610 marks

   (a) What is Carnot Cycle? Draw and explain it for a reversible process. (b) What does Gibbs function describe? Prove that Gibbs function for a (6) reversible isothermal and isobaric process is constant. (c) A heat engine absorbs 52.4 kJ of heat and exhausts 36.2 kJ of heat in each (4) (20) cycle. Calculate efficiency of heat engine and work done by engine per cycle. Q.7. (a) Derive Clausius - Claypron équation and also write its two conclusions. (10) (b) Prove that TV-=constant (6) (c) Air occupying 0.142 m³ at 2.04x10 is expanded isothermally to 1 atm and (4) (20) then cooled at constant pressure until it reaches its initial volume. Find work done on the gas.

6. Q. 820 marks

   Write Comprehensive notes on any two of the following: (10 each) (a) Newton's ring (b) Polarization by reflection (c) Doppler effect

Standard FPSC instructions

Printed on this and every CSS paper.

• Part-II is to be attempted on the separate Answer Book.
• All the parts (if any) of each question must be attempted at one place instead of at different places.
• Write Q. No. in the Answer Book in accordance with Q. No. in the question paper.
• No page/space be left blank between the answers. All the blank pages of the Answer Book must be crossed.
• Extra attempt of any question or any part of the attempted question will not be considered.