Kerala PSC Range Forest Officer – Forest and Wildlife (Physics) Previous Question Paper – 041/2025

The Commission publishes this paper without an answer key, so no answers are shown.

1. A uniform circular lamina has mass 100 g and radius 100 cm. A circular portion of radius 2 cm centred about a point located at a distance 4 cm from the centre O of the lamina is removed from it. Find the moment of inertia of the remaining portion of the lamina about an axis perpendicular to its plane and passing through O. (6)

2. A particle, initially at rest, is moving in a constant force field F along the direction of the force. Calculate the changes in the kinetic and potential energies of particle when its displacement from the initial position is S. (6)

3. A particle of mass m1 collides with a second particle, of mass m2 , at rest. After the collision, the particles move in opposite directions, the second particle moving with twice the speed of the first particle. Find the ratio of the masses of the particles, assuming that the collision is elastic. (6)

4. A particle is moving in a central force filed F (r ) = F (r ) rˆ , where r is its position vector with respect to the centre of force O and r̂ is the unit vector along r . Show that its orbital angular momentum about O is conserved and explain why the motion of the particle is restricted to the plane perpendicular the angular momentum. (6)

5. (a) Write down the three properties to be satisfied by a well-behaved
wave function.
(b) Briefly explain the condition for a wave function to be normalised.
(c) When can you say that two wave functions are orthogonal within
some given interval? (6)

6. (a) Write down the expression for a normalised wave function in one
dimension, for a particle in a box of width L.
(b) Find the probability that a particle in a box of width L can be found
between x = 0 and x = L n , when it is in the nth quantum state. (6)

7. (a) From where the energy comes when a liquid rises in a capillary tube
against gravity.
(b) The excess pressure inside a soap bubble of radius 10 cm is balanced
by 0.01 cm of liquid column. Determine the density of the liquid. Surface tension of soap solution is 0.03 N/m. Take acceleration due to gravity as 10 m/s2. (6)

8. (a) What do you mean by Modulus of elasticity?
(b) A wire 1 m long and 1 sq cm in cross section is found to stretch 0.1 cm
under a tension of 1000 kg. Compute the Young’s modulus of the material of the wire. Take acceleration due to gravity as 10 m/s2. (6)

9. Apply (∂Q/∂V)ₜ = T(∂P/∂T)ᵥ from thermodynamics to radiation to show that radiation-energy density is directly proportional to the fourth power of absolute temperature T. Q is heat, V is volume, and P is pressure. (4)

10. Obtain the expression for efficiency of carnot engine in terms of source and sink temperatures, respectively T1 and T2 and discuss how it leads to second law of thermodynamics. (4)

11. One mole of ideal gas expends isothermally at temperature T. If V1 and V2 are the initial and final volumes, obtain the expression for work done by the gas. Calculate the value of work in joules if the expansion is at 27°C to a pressure one-tenth the original. Gas constant R = 8.3 in SI system. (6)

12. Starting from the equation for the instantaneous charge on the capacitor when it is charged through an inductor and resistor connected in series, show that for oscillatory charging, the angular frequency of the circuit is (1/LC – R2/4L2)1/2. L is the inductance, C the capacitance and R resistance. (6)

13. Theoretically establish the existence of electromagentic wave that propagates through vacuum at the speed 3 × 108 m/s (6)

14. The Hall coefficient of certain semiconductor specimen is – 5 × 10–5 m3 C–1 from – 173°C to 127°C. Determine the nature of the semiconductor and identify the charge carriers and give reason. If the electrical conductivity of the specimen is 160 Ω–1 m–1, find the density and mobility of the charge carriers. (4)

15. Plot all represented by the Miller indices <110> in cubic lattice. (6)

16. Compare and justify your inferences of the two curves given. (6)

17. Explain how a shunt capacitor filter reduces ripple in a rectifier circuit and why its effectiveness depends on load resistance. (4)

18. Explain how an emitter resistor (RE) stabilises the Q-point against temperature variations in a CE amplifier. (6)

19. What will happen if the common-emitter (CE) amplifier used in an RC phase shift oscillator designed for a particular frequency is replaced with a common-collector (CC) amplifier? (6)

20. Using the 2’s complement, subtract 101012 from 110102. (4)

21. What is EPROM and EEPROM? Why is EEPROM considered more versatile in modern applications? (4)

22. Write an assembly language program in 8085 for adding two 8-bit numbers stored in memory locations and storing the 8-bit sum in another memory location. (4)

23. Find the decimal and binary equivalents of the hexadecimal number, 2D716? (5)

24. Simplify the Boolean expression y = (ABC)̅ + AB̅C + ABC̅ and draw its simplified logic circuit. (5)

25. A transducer provides 9 identical readings, followed by tenth reading that is 20 units lower. What is the standard deviation of the data set? (4)

26. What is the equation of the line that best approximates the relationship between the x and y values in the given data set.
x : 0.04 0.15 0.3 1.0 2.0
y: 3 16 13 70 90 (6)

27. A voltmeter with 5000 Ω coil at 15°C and a temperature coefficient of 0.004/°C is used to measure 200 V. What is the percentage error in the reading at 40°C. (6)

28. Assess the potential stability of a newly discovered element with atomic number Z = 130. (4)

29. Critically evaluate the assumptions of the Bohr-Wheeler fission model and discuss its limitations in accounting for asymmetric fission fragment distributions. (6)

30. How is radon gas (atomic number Z = 86) generated, released into the environment and detected and what explains its increased levels in the air before an earthquake? (6)

31. Explain the structure of the Sun, highlighting its different layers and their characteristics. Discuss the role of sunspots, solar flares and coronal mass ejections (CMEs) in solar activity and analyse their impact on Earth’s magnetosphere and technological systems. (5)

32. Describe the temperature and pressure variations across different layers of Earth’s atmosphere. Discuss how the scale height affects atmospheric density and explain the role of ionospheric electric fields in radio communication and satellite navigation systems. (5)

33. Explain the characteristics of lasers and obtain Einstein coefficients. Discuss the working principle of a semiconductor laser and its applications in modern communication systems. (6)

34. Explain the working principle of optical fiber communication and discuss the advantages of fiber optic communication over traditional cable-based systems. Discuss the role of numerical aperture in light propagation through an optical fiber and justify the choice of single-mode fibres for long-distance communication. (6)

35. How the material choice and device structure influence the spectral distribution and efficiency of an LED. Support your answer with an example. (4)

36. Compare and contrast PIN photodiodes and Avalanche photodiodes (APDs) in terms of structure, responsivity and applications in optical communication. (4)

37. Explain with suitable examples how dimensionality affects the physical and electronic properties of nanostructures. (5)

38. Compare Top-Down and Bottom-Up nanofabrication techniques with respect to scalability, precision and cost. Provide an application example of each. (5)