# Basic Electronics Important Questions -Unit-1 (FAQ)

Basic Electronics Important questions  –Unit-1

Note: Read the questions in the following order   i. Assignment questions ii. Class test  iii. Expected questions iv.  Tutorials For every unit.

Unit1:

ASSIGNMENT- UNIT 1

1.  Explain the working of Bridge rectifier in detail with a neat circuit diagram and derive the expression for ripple factor and efficiency. 10M.
2. Explain the working of PN-junction diode in detail in forward and reverse bias conditions. 10M.
3. A 230v, 60 Hz voltage is applied to the primary of a step down center tapped transformer of a FWR with turns ratio 5:1 is connected to a load resistance of 1 KΩ i. i. Determine voltage across the load. ii. DC current through the load. If there is a resistance of 100Ω for the transformer secondary and diode forward Resistance is given as 10Ω.

1. Write the expression of diode current equation and explain each term in detail.
2. Define cut in or threshold voltage of a diode. Give the values of Vof Si and Ge diode.
3. Write the differences between Extrinsic and Intrinsic semiconductors.
4. What are P-type and N-type semiconductors?
5. Write in detail about Drift and Diffusion currents.
6. Draw the Energy Band Diagrams of an insulator, semiconductor, Conductor.
7. Write the differences between insulators, conductors and semi conductors.
8. Define the following   a. Mobility b. Conductivity  c. Mass Action law. d.Fermi level in semi conductors.
9. Draw the diagrams for Fermi-level in Intrinsic, N-type and P-type semi conductors and write the formula for EF in the above two cases.
10. Define Hall Effect and write the uses or applications of Hall Effect.
11. What properties of semi conductor are defined from Hall Effect?
12. What is a diode and write the applications of Diode.
13. Draw the VI-Characteristics of a diode. And calculate Static and Dynamic resistances from the characteristics.
14. Write about diffusion and Transition capacitances of a diode.
15. Define avalanche breakdown and zener breakdown.
16. What is avalanche effect and zener effect?
17. What is a rectifier? Differentiate between Half Wave Rectifier and Full Wave Rectifier.
18. Draw the equivalent circuit of practical Diode under forward bias and Reverse Bias.
19. Draw the equivalent circuit of ideal Diode under forward bias and Reverse Bias.
20. Define Peak Inverse Voltage (PIV) of a diode in a rectifier circuit. Write the PIV values in HWR, FWR and Bridge Rectifier.
21. Define the following i. Ripple factor       ii. Regulation or Percentage of Regulation. iii. From factor and peak factor. iv. Efficiency of a rectifier  v. RMS value and average value of voltage or current wave in half wave rectifier.
22. Write the applications of Zener Diode.
23. Explain how Zener diode works as a regulator.
24. What is the concentration of holes in Si crystals having donor concentration of 1.4 x 1024/m3 when the intrinsic carrier concentration is 1.4 x 1018/m3 ? Find the ratio of electron to hole concentration.
25. Problems on motilities of n-type and p-type semiconductors.
26. An n-type Ge crystal has a current density of 100A/m2. The crystal has a resistivity of 0.5 Ω-m and electron mobility of 0.4 m2/V-s. Calculate the drift velocity and the time taken by the electron to travel 10 micrometer in the crystal. Assume q= 1.6 x 10-19
27. Problems on Fermi levels.
28. Problems on diode current equation in forward bias and reverse bias.
29. Write the advantages of full wave and bridge rectifiers over half wave rectifier.

1. Define Hall Effect. Derive the expression for Hall voltage and hall coefficient and explain the uses of Hall Effect.
2. Derive the expression for transition and diffusion capacitances of a diode.
3. Explain the working of Zener Diode as a regulator.
4. Derive the expression for ripple factor and efficiency of a Half Wave rectifier and full wave rectifier.
5. Derive the expression for ripple factor and efficiency of a bridge rectifier.
6. Compare half wave rectifier, FWR and Bridge rectifier in terms of (ripple factor, percentage of regulation, efficiency, PIV, from factor and peak factor etc…… read the comparison table in text book).
7. How will you find the dynamic and static resistance of the diode using a graph?
8. What is an ideal diode? How can it be represented as a switch? Draw the equivalent circuit and its characteristics.
9. Draw the VI-Characteristics of a PN junction diode in forward and reverse biased conditions. Define forward resistance and reverse resistances and explain how they can be obtained from the characteristics.
10. Draw the circuit diagram of a half wave rectifier and explain its operation with wave forms.
11. Draw the circuit diagram of bridge rectifier and explain its operation with wave forms.
12. Draw the circuit diagram of a full wave rectifier and explain its operation with wave forms. What is its advantage over half wave rectifier?
13. What is static resistance of the diode? How will you find the dynamic resistance?
14. Explain the zener and avalanche thermal breakdown mechanisms. What will be their thermal coefficients?
15. How is a PN junction formed? Draw the circuit diagram of PN-Junction diode in forward bias and reverse bias. Explain its operation and give VI-characteristics.
16. What is a rectifier? Draw the circuit diagram for bridge rectifier with LC-filter and explain its operation.
17. Explain bridge wave rectifier with circuit diagram and output wave forms. Find      i. RMS value of current.   ii. Ripple factor.  iii. TUF   iv. Efficiency   v. Peak factor.
18. Explain avalanche breakdown and zener breakdown in PN diode.
19. Derive the expression for ripple factor of a FWR (or HWR/ Bridge) with shunt capacitance filter.
20. Derive the expression for ripple factor of a FWR (or HWR/ Bridge) with series inductance filter.
21. Derive the expression for ripple factor of a FWR (or HWR/ bridge) with LC π section filter.
22. Derive an expression for current in a diode.
23. Compare drift and diffusion currents.

Tutorial -1 Questions

1. A Full Wave Rectifier has a Secondary Voltage of 230V from one-end of the transformer to ground. then calculate i. DC load Current. ii. RMS value of output current. If diode has a resistance of 10Ω and the resistance of secondary winding is negligible. Given RL=5KΩ.
2. Find the conductivity of P-type semi conductor, if the concentration of holes is 4.2X1022atoms/m3 and mobility of holes is 1800 Cm2/V.
3. Write the expression for Hall voltage and find Hall voltage if the Magnetic field strength of 1000 Wb/m2 where the current flowing through the semi conducting material is 9A. Width of semi conducting material is 2m with resistivity of 100 Mhos-m. Also find the Hall coefficient?
1. Write a short note on P-type and N-type semi conductors.

ALL THE BEST

Prepared by                                                                                       P.Lakshmi Prasanna

## Author: Lakshmi Prasanna Ponnala

Completed M.Tech in Digital Electronics and Communication Systems.

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