Fundamentals of Electronics (4311102) - Summer 2024 Solution

Question 1 [14 marks]

Answer any seven out of ten.

Question 1(1) [2 marks]

Define resistor and give its unit.

Answer: A resistor is an electronic component that opposes the flow of electric current. Its unit is Ohm (Ω).

Table: Resistor Properties

Mnemonic: "Resistors Oppose Current" (ROC)

Question 1(2) [2 marks]

Give two examples of active and passive components each.

Answer:

Table: Electronic Components Classification

Mnemonic: "TARD" - Transistors And Resistors Differ

Question 1(3) [2 marks]

Draw symbols of any two semiconductor devices.

Answer:

Diagram:

Mnemonic: "Diodes Direct, Transistors Transfer"

Question 1(4) [2 marks]

Differentiate between intrinsic and extrinsic semiconductor.

Answer:

Table: Intrinsic vs Extrinsic Semiconductors

Mnemonic: "Pure In, Doped Ex"

Question 1(5) [2 marks]

LED stands for _________________.

Answer: LED stands for Light Emitting Diode.

Diagram:

Mnemonic: "Light Emitters Dazzle"

Question 1(6) [2 marks]

State any two applications of Photo-diode.

Answer:

Table: Photo-diode Applications

Mnemonic: "Light Sensing Communication" (LSC)

Question 1(7) [2 marks]

List the types of transistor and draw their symbols.

Answer:

Types of Transistors:

1. NPN Transistor
2. PNP Transistor

Diagram:

Mnemonic: "Not Pointing iN, Pointing outP"

Question 1(8) [2 marks]

Give the value of forward voltage drop of Germanium and Silicon diode.

Answer:

Table: Forward Voltage Drop Values

Mnemonic: "Germanium's Three, Silicon's Seven" (0.3V, 0.7V)

Question 1(9) [2 marks]

The _________________ diode can be used as a light detector.

Answer: The Photodiode can be used as a light detector.

Diagram:

Mnemonic: "Photo Detects Light" (PDL)

Question 1(10) [2 marks]

Define Q-factor of a coil.

Answer: Q-factor (Quality factor) of a coil is the ratio of its inductive reactance to its resistance, indicating how efficiently it stores energy.

Table: Q-Factor

Mnemonic: "Quality equals Reactance over Resistance" (QRR)

Question 2(a) [3 marks]

Explain colour coding method of resistor.

Answer:

Resistor color coding uses colored bands to indicate resistance value and tolerance.

Table: Resistor Color Code

For a 4-band resistor:

• First band: First digit
• Second band: Second digit
• Third band: Multiplier
• Fourth band: Tolerance

Mnemonic: "Bad Boys Race Our Young Girls But Violet Generally Wins" (Colors in order: Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White)

Question 2(a) OR [3 marks]

Explain Light Dependent Resistor with its characteristics.

Answer:

LDR is a resistor whose resistance decreases when light intensity increases.

Characteristics of LDR:

Table: LDR Properties

Diagram:

Mnemonic: "Light Up, Resistance Down" (LURD)

Question 2(b) [3 marks]

Explain classification of capacitors in detail.

Answer:

Capacitors are classified based on dielectric material and construction.

Table: Capacitor Classifications

Diagram:

Mnemonic: "CEPT" (Ceramic, Electrolytic, Polyester, Tantalum)

Question 2(b) OR [3 marks]

Explain classification of inductor in detail.

Answer:

Inductors are classified based on core material and construction.

Table: Inductor Classifications

Diagram:

Mnemonic: "Air Iron Ferrite Toroid" (AIFT)

Question 2(c) [4 marks]

State and explain Faraday's laws of Electromagnetic Induction.

Answer:

Faraday's laws explain how electromagnetic induction works.

Faraday's First Law: When a magnetic field linked with a conductor changes, an EMF is induced in the conductor.

Faraday's Second Law: The magnitude of induced EMF is proportional to the rate of change of magnetic flux.

Table: Faraday's Laws Summary

Diagram:

Mnemonic: "Change Magnetic Field, Create Electric Current" (CMFCEC)

Question 2(c) OR [4 marks]

Enlist specifications of capacitors and explain two in detail.

Answer:

Specifications of Capacitors:

1. Capacitance value
2. Voltage rating
3. Tolerance
4. Leakage current
5. Temperature coefficient

Detailed Explanation:

Capacitance Value: The amount of charge a capacitor can store per volt, measured in Farads (F).

Voltage Rating: The maximum voltage that can be applied without damaging the capacitor.

Table: Capacitor Specifications

Diagram:

Mnemonic: "Capacitors Very Tolerant of Low Temperatures" (CVTLT)

Question 2(d) [4 marks]

Write colour band of 47Ω±5% resistance.

Answer:

For 47Ω±5% resistor, the color bands are:

Table: Color Bands for 47Ω±5%

Diagram:

Mnemonic: "Yellow Violets Bring Gold" (The colors of the bands)

Question 2(d) OR [4 marks]

Calculate value of resistor and tolerance for a given colour code: Brown, Black, yellow.

Answer:

Table: Interpretation of Brown, Black, Yellow

Calculation: 1st digit: 1 2nd digit: 0 Multiplier: 10⁴

Value = 10 × 10⁴ = 100,000Ω = 100kΩ

No 4th band means ±20% tolerance

Diagram:

Mnemonic: "Big Black Yield" (Brown-Black-Yellow)

Question 3(a) [3 marks]

Define doping. Give the name of semiconductor materials fabricated by doping with an example of each.

Answer:

Doping is the process of adding impurities to a pure semiconductor to modify its electrical properties.

Table: Doped Semiconductors

Diagram:

Mnemonic: "Positive has Plus Holes, Negative has Numerous Electrons" (PHNE)

Question 3(a) OR [3 marks]

Define Ripple factor, Peak Inverse Voltage (PIV), Rectification efficiency.

Answer:

Table: Rectifier Terms

Diagram:

Mnemonic: "Ripples Peak Efficiently" (RPE)

Question 3(b) [3 marks]

Explain working of Crystal diode.

Answer:

Crystal diode is a point-contact diode made with a semiconductor crystal.

Table: Crystal Diode Properties

Diagram:

Mnemonic: "Crystal Detects Radio Frequencies" (CDRF)

Question 3(b) OR [3 marks]

Explain working of photodiode.

Answer:

Photodiode converts light energy into electrical current when operated in reverse bias.

Table: Photodiode Characteristics

Diagram:

Mnemonic: "Light In, Current Out" (LICO)

Question 3(c) [4 marks]

Explain half-wave rectifier with circuit diagram and waveforms.

Answer:

Half-wave rectifier converts AC to pulsating DC by allowing current flow only during positive half cycles.

Circuit Diagram:

Waveforms:

Table: Half-Wave Rectifier Properties

Mnemonic: "Half Wave Passes Half" (HWPH)

Question 3(c) OR [4 marks]

Explain full-wave rectifier with circuit diagram and waveforms.

Answer:

Full-wave rectifier converts both halves of AC input to pulsating DC output.

Circuit Diagram (Bridge type):

Waveforms:

Table: Full-Wave Rectifier Properties

Mnemonic: "Full Wave Makes Full Use" (FWMFU)

Question 3(d) [4 marks]

Draw and explain VI characteristics of PN junction diode.

Answer:

VI Characteristics:

Table: PN Junction Diode Characteristics

Forward Bias: Positive voltage to P-side, current flows easily after threshold. Reverse Bias: Positive voltage to N-side, only small leakage current flows.

Mnemonic: "Forward Flows, Reverse Restricts" (FFRR)

Question 3(d) OR [4 marks]

Write difference between P-type and N-type semiconductor.

Answer:

Table: P-type vs N-type Semiconductor

Diagram:

Mnemonic: "Positive has Plus Holes, Negative has Numerous Electrons" (PHNE)

Question 4(a) [3 marks]

Explain the principle of operation of LED.

Answer:

LED (Light Emitting Diode) emits light when forward biased due to electron-hole recombination.

Principle of Operation: When forward biased, electrons from N-side move to P-side and recombine with holes, releasing energy as photons (light).

Table: LED Operation

Diagram:

Mnemonic: "Forward Current Emits Light" (FCEL)

Question 4(a) OR [3 marks]

State applications of LED.

Answer:

Table: LED Applications

Diagram:

Mnemonic: "Display Lights In Clever Signals" (DLICS)

Question 4(b) [4 marks]

Explain Zener diode as voltage regulator.

Answer:

Zener diode maintains constant output voltage despite input voltage fluctuations when operated in reverse breakdown region.

Circuit:

Working:

• Series resistor limits current
• Zener operates in breakdown region
• Maintains constant voltage across load

Table: Zener Regulator Characteristics

Mnemonic: "Zeners Break to Regulate" (ZBR)

Question 4(b) OR [4 marks]

Give limitations of zener voltage regulator.

Answer:

Table: Limitations of Zener Voltage Regulator

Diagram:

Mnemonic: "Power Current Temperature Efficiency Noise" (PCTEN)

Question 4(c) [7 marks]

Discuss the necessity of filter circuit in rectifier. List various types of filter circuits used in rectifier and explain any one with neat diagram.

Answer:

Necessity of Filter Circuit: Rectifier output contains AC ripple that must be removed for smoother DC. Filters reduce these ripples to provide steady DC output.

Types of Filter Circuits:

1. Capacitor filter (Shunt capacitor)
2. LC filter
3. π-filter (Pi-filter)
4. RC filter

Explanation of Capacitor Filter:

Circuit Diagram:

Working:

• Capacitor charges during voltage peaks
• Discharges slowly during voltage drops
• Maintains output voltage between peaks
• Reduces ripple voltage

Table: Capacitor Filter Characteristics

Waveforms:

Mnemonic: "Capacitors Hold Voltage During Drops" (CHVDD)

Question 5(a) [3 marks]

Define e-waste. List common e-waste items.

Answer:

E-waste refers to discarded electronic devices and components that have reached the end of their useful life.

Table: Common E-waste Items

Diagram:

Mnemonic: "Computers, Communication, Components, Home Appliances" (CCCHA)

Question 5(b) [3 marks]

State and explain various strategies of e-waste management.

Answer:

Table: E-waste Management Strategies

Diagram:

Mnemonic: "3R's

Question 5(c) [4 marks]

Explain transistor as switch.

Answer:

Transistor can function as an electronic switch by operating in either cutoff (OFF) or saturation (ON) region.

Table: Transistor Switch Operation

Circuit Diagram:

Working:

• When input is HIGH: Transistor saturates, acts like closed switch
• When input is LOW: Transistor cuts off, acts like open switch

Mnemonic: "No Base No Current, Apply Base Connect Circuit" (NBNC-ABC)

Question 5(d) [4 marks]

Derive relation between α and β for CE configuration of transistor.

Answer:

In transistors, α (alpha) and β (beta) are current gain parameters.

Definitions:

• α = IC/IE (Common Base current gain)
• β = IC/IB (Common Emitter current gain)

Derivation: Since IE = IC + IB, we can write: α = IC/IE = IC/(IC + IB)

Dividing numerator and denominator by IB: α = (IC/IB)/[(IC/IB) + 1] = β/(β + 1)

Therefore: β = α/(1-α)

Table: Relationship between α and β

Diagram:

Mnemonic: "Beta equals Alpha divided by One minus Alpha" (BAOA)