1. Concept of Basic Electrical and Electronics Engineering

1.1 Basic Concepts

Ohm’s Law

• Ohm’s Law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R).
  Formula:

  $$V=I\times R$$

Electric Voltage, Current, Power, and Energy

• • Voltage (V): Potential difference between two points (measured in Volts).

  • Current (I): Flow of electric charge (measured in Amperes).

  • Power (P): Rate of energy transfer (measured in Watts).

    $$P=V\times I$$

  • Energy (E): Total work done (measured in Joules).

    $$E=P\times t$$

Conducting and Insulating Materials

• • Conductors: Allow free electron flow (e.g., copper, aluminum).

  • Insulators: Resist electron flow (e.g., rubber, glass).

Series and Parallel Circuits

• • Series Circuit: Components connected end-to-end (same current, voltage divides).

  • Parallel Circuit: Components connected across common points (same voltage, current divides).

Star-Delta and Delta-Star Conversion

• Used for simplifying complex resistor networks.

  • Star (Y) to Delta (Δ):

    $$R_{ab}=R_1+R_2+\frac{R_1{R}_2}{R_3}$$

  • Delta (Δ) to Star (Y):

    $$R_a=\frac{R_{ab}{R}_{ac}}{R_{ab}+R_{bc}+R_{ca}}$$

Kirchhoff’s Laws

• • KCL (Current Law): Sum of currents entering a node = Sum leaving.

  • KVL (Voltage Law): Sum of voltages in a closed loop = 0.

Linear & Non-Linear Circuits

• • Linear: Follows superposition (Ohm’s Law holds).

  • Non-Linear: Does not follow superposition (diodes, transistors).

Bilateral & Unilateral Circuits

• • Bilateral: Current flows both ways (resistors).

  • Unilateral: Current flows one way (diodes).

Active & Passive Circuits

• • Active: Contains energy sources (batteries, transistors).

  • Passive: No energy sources (resistors, capacitors).

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1.2 Network Theorems

Superposition Theorem

• In a linear circuit, the response (voltage/current) due to multiple sources is the sum of responses due to each source acting alone.

  
  

Thevenin’s Theorem

• Any linear network can be replaced by an equivalent circuit with a voltage source (Vth) and series resistance (Rth).

Norton’s Theorem

• Any linear network can be replaced by an equivalent current source (In) and parallel resistance (Rn).

Maximum Power Transfer Theorem

• Maximum power is transferred when load resistance equals source resistance.

R-L, R-C, R-L-C Circuits

• • R-L Circuit: Inductor resists current changes.

  • R-C Circuit: Capacitor resists voltage changes.

  • R-L-C Circuit: Exhibits resonance at $f_r=\frac{1}{2\pi \sqrt{LC}}$.

Resonance in AC Circuits

• • Series Resonance: Minimum impedance, maximum current.

  • Parallel Resonance: Maximum impedance, minimum current.

Active & Reactive Power

• • Active Power (P): Real power (Watts).

  • Reactive Power (Q): Stored power (VAR).

  • Apparent Power (S): $S=\sqrt{P^2+Q^2}$.

1.3 Alternating Current Fundamentals

Generation of AC

• Produced by rotating a coil in a magnetic field (sinusoidal waveform).

  $$V(t)=V_{max}\sin (\omega t)$$

Peak, RMS, and Average Values

• • Peak Value: Maximum amplitude.

  • RMS Value: $V_{rms}=\frac{V_{max}}{\sqrt{2}}$.

  • Average Value: $V_{avg}=0.637\times V_{max}$.

Three-Phase System

• Three AC voltages 120° apart, used for efficient power transmission.

  Image Reference:

  • Sinusoidal AC Waveform

  • Three-Phase Voltage Waveform

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1.4 Semiconductor Devices

Semiconductor Diode

• • Characteristics: Forward bias (conducts), Reverse bias (blocks).

  • Applications: Rectifiers, clippers.

BJT (Bipolar Junction Transistor)

• • Configurations: Common Emitter, Base, Collector.

  • Biasing: Fixed, Emitter, Voltage Divider.

MOSFET & CMOS

• • MOSFET: Voltage-controlled device (high input impedance).

  • CMOS: Complementary MOSFET (low power).

  Image Reference:

  • Diode I-V Curve

  • BJT Configurations Diagram

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1.5 Signal Generators

Oscillators

• Generate periodic waveforms (sine, square, triangle).

  • RC Oscillator: Phase-shift, Wien bridge.

  • LC Oscillator: Hartley, Colpitts.

  • Crystal Oscillator: High stability.

    
    

    
    

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1.6 Amplifiers

Classification

• • Class A: Linear, low distortion.

  • Class B: Push-pull, efficient.

  • Class AB: Compromise between A & B.

Power BJTs & Tuned Amplifiers

• • Power BJTs: Handle high currents.

  • Tuned Amplifiers: Selects specific frequencies.

Op-Amps

• High-gain differential amplifiers (feedback-based).