Search, filter, and study UPSC Civil Services & IFoS Physics past year questions with rigorous derivations, formulas, and step-by-step solutions.
Explain classical theory of diamagnetism. Show that the susceptibility of diamagnetic substances is directly proportional to the atomic number. Why all the electrons in an atom contribute to diamagnetism ?
With a neat circuit diagram, explain the working of Wien-Bridge oscillator.
What will be the frequency of Josephson current, if a d.c. voltage of 4\cdot 0\ \mu\text{V} is applied across a Josephson junction?
Draw the crystal structure of \text{CaF}_2 indicating the positions of cations and anions. What are their respective coordination numbers?
Consider an n-channel JFET which has \text{I}_{\text{DSS}} = 15\text{ mA} and pinch-off voltage \text{V}_\text{p} = -5\text{ V}. If \text{V}_{\text{GS}} = -1\cdot 5\text{ V}, how much will the drain current \text{I}_\text{D} be? What will be the minimum value of \text{V}_{\text{DS}} for pinch-off to occur at \text{V}_{\text{GS}} = -1\cdot 5\text{ V}?
Consider the BJT amplifier circuit given below with the following parameters : d.c. current gain \beta_{\text{dc}} = a.c. current gain \beta_{\text{ac}} = 100 \text{I}_\text{B} = 20\ \mu\text{A} for \text{V}_\text{B} = 0\cdot 7\text{ V}, and \text{i}_\text{b} = \pm 2\ \mu\text{A} for \text{v}_\text{i} = \pm 10\text{ mV}. Determine the values of \text{V}_{\text{CE}}, input impedance and voltage gain \text{A}_\text{v}.
Derive diffraction conditions using reciprocal lattice concept. What are these conditions known as ?
With the help of a schematic diagram, describe the structure of n-depletion MOSFET. Draw and describe its drain and transfer characteristics.
(i) Determine the input and output impedances of the amplifier in given figure. The op-amp datasheet gives Z_{\text{in}} = 2\text{ M}\Omega, Z_{\text{out}} = 75\ \Omega and A_{\text{ol}} = 200,000 (open loop voltage gain). (ii) Find the closed-loop voltage gain.
Explain Gell-Mann and Ne'eman SU(3) symmetry for the classification of elementary particles — baryons and mesons.
Why does a neutron star have a magnetic field if it is composed of neutrons?
What is the age of a fossil that contains 6\text{ g} of carbon {}^{14}\text{C} and has a decay rate of 27\text{ decays per minute} ? Given : Ratio \frac{{}^{14}\text{C}}{{}^{12}\text{C}} = 1\cdot 3 \times 10^{-13}, Half life (T_{1/2}) of {}^{14}\text{C} = 5730\text{ yrs}.
(i) K^+ \longrightarrow \Pi^+ + \Pi^+ + \Pi^- (ii) \Pi^+ + p \longrightarrow \Pi^+ + \Pi^+ + n (iii) \Pi^+ + p \longrightarrow \Delta^{++} \longrightarrow \Pi^+ + p (iv) \Sigma^\circ \longrightarrow \lambda^\circ + \gamma (v) \Sigma^+ \longrightarrow \lambda^\circ + e^+ + u_e (vi) K^- + p \longrightarrow K^+ + K^\circ + \Omega^- (vii) \Pi^\circ \longrightarrow \gamma + e^+ + e^- (viii) \Sigma^- \longrightarrow n + e^- + \bar{\nu}_e (ix) \lambda^\circ \longrightarrow p + e^- + \bar{\nu}_e (x) e^+ + e^- \longrightarrow \gamma + \gamma Name the interactions via which the above nuclear decays occur :
On the basis of conservation laws, explain whether the following reactions are allowed or forbidden : (i) \pi^- + \text{p} \longrightarrow \Sigma^+ + \text{K}^- (ii) \text{K}^- + \text{p} \longrightarrow \Omega^- + \text{K}^+ + \text{K}^0 (iii) \Omega^- \longrightarrow \Xi^0 + \pi^- (iv) \pi^+ + \text{p} \longrightarrow \text{p} + \text{p} + \bar{\text{n}} (v) \Sigma^+ \longrightarrow \Lambda^0 + \text{K}^+
What do you understand by nuclear forces ? Explain meson theory of exchange forces.
How could you establish that \nu_e and \bar{\nu}_e are two different particles ?
What do you understand by the critical size of a nuclear reactor? Write down the common features of nuclear reactors used for the production of electricity.
Justify the fact that the electrons are emitted from nuclei in \beta-decay but they cannot be contained inside the nuclei.
Establish the Rutherford's scattering cross section formula for \alpha-particle by considering the standard assumptions and symbols.
What do you understand by the critical size of a reactor ? Explain the main features of nuclear reactors.