UPSC Physics Optional PYQs (CSE & IFoS)PYQs

How one can obtain the various types of information about the physical conditions on the stellar surface using thermal ionization equation to interpret the stellar spectra.

Define the efficiency of a Carnot Engine. An engine is designed to have an efficiency of 25\% and to absorb heat at a temperature of 267^\circ\text{ C}. Find the maximum temperature at which it can exhaust heat.

Write a short note on Debye's theory of specific heat.

Write a short note on Adiabatic demagnetisation.

Write a short note on Clausius-Clapeyron equation.

What is the most probable distribution of speeds in a large number of molecules of a gas and indicate the steps for its derivation.

A tank whose capacity is 0.1\text{ m}^3 contains helium at a pressure of 10\text{ atmospheres} and a temperature of 20^\circ\text{C}. A rubber weather balloon is inflated with this helium.

(i) When the pressure of helium in the balloon is 1\text{ atmosphere}, its temperature is -40^\circ\text{ C}. Find the volume of the balloon.

(ii) Eventually the helium in the balloon absorbs heat from the air around ii and returns to 20^\circ\text{ C}. Find the volume of the balloon at this time.

For an R-L- C series resonant circuit, show that f_0 = \sqrt{f_1 f_2}, where f_0 is the resonance frequency and f_1, and f_2 are the half-power frequencies. Is this relation true for a parallel resonance circuit in which R, L and C are connected in parallel to each other? Explain.

Calculate the voltage drops across R and across L.

A series R-L circuit has a constant d.c. voltage V applied at the time t = 0 by closing a switch. Derive an expression for the current in the circuit.

Current is flowing in a single-turn circular coil of radius 0.1\text{ m} such that at a point 5\text{ mm} from the centre of the coil on the axis perpendicular to the plane of the coil the magnetic field is 0.1\text{ mT}. Find the current in the coil. Hence calculate the magnetic moment of the current carrying coil.

Show that the steady -state energy is stored in the magnetic field.

The introduction of the displacement current is one of the major contributions of Maxwell. Discuss.

Using Maxwell's equations, derive the electromagnetic wave equations for a conducting medium and solve it.

What is the limiting case of a metallic conductor in the above case ? Explain

At what time are these voltage drops equal?

Find the power dissipated by R and power stored in L.

How does the resolving power of a microscope differ from that of a telescope ? Find the resolving power of an electron microscope that uses 15\text{ Key} electrons, assuming that this is equal to the electron wavelength.

Write a short note on Holography.

When fixed at both ends, a wire under tension of 900\text{ N} and having a linear density 10^{-2}\text{ kg/m} is resonant at the frequency of 420\text{ Hz}. The next higher frequency at which it resonates is 490\text{ Hz}. What is the length of the wire.