UPSC Physics Optional PYQs (CSE & IFoS)PYQs

What are the main applications of JFET? Discuss their advantages over bipolar transistors. Explain the working of n-channel JFET with the help of a schematic diagram.

(i) Discuss the variation of free carrier concentration with temperature for an intrinsic and extrinsic semiconductors. (ii) Explain the effect of negative and positive voltage feedback on an amplifier characteristics.

Write down the characteristics of an ideal operational amplifier. Explain the term virtual ground. Draw a circuit diagram showing virtual ground in an operational amplifier.

(i) Show that a negative logic OR gate is like a positive logic AND gate. (ii) Distinguish between Hadrons and Leptons.

Explain Meissner effect and Josephson effect. Describe their applications in the field of superconductivity.

(i) What are sequential switching circuits (ii) Describe a simple sequential circuit. (iii) Describe a clocked RS Flip-Flop, (iv) Briefly describe ROMs.

Combinational switching circuit can perform an addition of the numbers held in two registers. (i) Write down the math table for the addition of two bits. (ii) Write down a Boolean expression for the necessary circuit functions. (iii) Arrive at the Exclusive-OR function. (iv) Draw the logic diagram for the circuit which performs the addition.

Explain a solar cell employing its characteristics on output quantity Venus quantities like load current, radiance and temperature.

(i) FETs have unique properties which make BJTs not suitable for some important applications. What are these most important FET applications? (ii) Briefly describe FETs as variable resistors.

(i) Give a qualitative account of BCS theory of superconductivity. (ii) Obtain an expression for conductivity of an intrinsic semiconductor. How does it vary with temperature? (iii) The resistivity of an intrinsic semiconductor is 4.5\text{ ohm-m} at 20^\circ\text{C} and 2.0\text{ ohm-m} at 32^\circ\text{C}. Calculate the energy band gap.

(i) Obtain reciprocal lattice to normal BCC lattice. (ii) Describe Josephson junction and the effect. How is it exploited in the formation of a SQUID? Write down the applications of a SQUID. (iii) Distinguish between intrinsic and extrinsic semiconductors. Explain the concept of hole.

Explain why superconductors are perfect diamagnets.

Which one of these mechanisms shows a negative dynamic resistance? Why?

Discuss the different breakdown mechanisms for a reverse biased Zener diode.

A Zener diode of 1\text{ W} power has a dynamic resistance of 10\text{ m}\Omega at the breakdown voltage of 3\text{ V}. What will be the fluctuations in the current through the diode if the voltage fluctuates by 100\text{ mV}? What will happen to the diode ? Why?

What are the salient characteristics of ferromagnetic ? Explain how the Curie law of paramagnetism is modified to the Curie - Weiss law.

Do these mechanisms have different temperature coefficients? Explain.

A circuit of a NOT gate is given in the figure below. Explain how you will determine the values of the resistances R_B, R and R_L.

What is Meissner effect? Superconducting tin has a critical temperature of 3.7 K in zero magnetic field and critical field at 0 K is 306 gauss. Determine the critical field at 2K.

A junction diode in series with a parallel combination of a large resistor and a capacitor acts as a linear detector of amplitude modulated waves. Explain the action.