� 1. Practical: Basic Diode Circuits
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虋 Objective:
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Understand how diodes work in DC and AC circuits
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Measure voltage drops across diode-based circuits
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Observe rectification (AC to DC conversion)
궡 Key Theory:
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Diode Function: Allows current in one direction (forward bias), blocks it in reverse.
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Forward Voltage Drop: Typically ~0.7V for silicon diodes.
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Half-Wave Rectifier: Uses one diode to allow only one half of the AC waveform
through.
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Full-Wave Rectifier: Uses four diodes (bridge) to rectify both halves of the AC
waveform.
뭆 Basic Operations:
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Construct circuits on a breadboard using a diode, resistor, and AC source.
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Use a multimeter to measure:
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Voltages V1,V2,V1−V2V_1, V_2, V_1 - V_2V1,V2,V1−V2
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Current through resistor (using Ohm’s law if needed).
Use an oscilloscope (DC coupling) to observe:
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Input vs. output waveform
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Ch1 - Ch2 (di erential voltage)
굖 Important Points:
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Always label axes on oscilloscope.
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Zero reference line is critical for understanding waveform shape.
� 2. Practical: Phasor Relationships (RC and RL Circuits)
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虋 Objective:
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Analyze phase di erences in RC and RL circuits.
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Understand the concept of phasors in AC circuit analysis.
궡 Key Theory:
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Phasors represent sinusoidal voltages/currents as rotating vectors.
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RC Circuit:
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Voltage across resistor is in phase with current.
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Voltage across capacitor lags the current.
RL Circuit:
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Voltage across inductor leads the current.
뭆 Basic Operations:
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Build RC and RL circuits on a breadboard with resistor and either capacitor or
inductor.
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Use a signal generator (100 kHz, 2V peak).
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Connect oscilloscope probes to:
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Signal generator output
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Across R and C/L
Measure:
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Time period TTT
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Time shift XXX
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Phase angle: Phase (degrees)=XT×360∘\text{Phase (degrees)} = \frac{X}{T}
\times 360^\circPhase (degrees)=TX×360∘
굖 Important Skills:
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Interchange R and C/L to observe changes.
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Convert voltages to rectangular form (real + j imaginary).
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Draw phasor diagrams to visually represent relationships.
� 3. Practical: Transformer Design and Implementation
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虋 Objective:
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Design and build a working single-phase step-down transformer.
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Transformer Principle: Mutual induction between primary and secondary coils
transfers energy.
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Step-down transformer: Reduces voltage (e.g., from 100V to 12V).
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Key equations:
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Turns ratio: N1N2=V1V2\frac{N_1}{N_2} = \frac{V_1}{V_2}N2N1=V2V1
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Induced EMF: E=4.44fϕmNE = 4.44 f \phi_m NE=4.44fϕmN
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VA rating: P=V1I1=V2I2P = V_1 I_1 = V_2 I_2P=V1I1=V2I2
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Cross-sectional area: a=πD24a = \frac{\pi D^2}{4}a=4πD2
뭆 Basic Operations:
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Calculate:
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Number of turns: using turns/volt value (e.g., 3.6)
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Wire diameter → use SWG tables
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Current density and cross-section
Build:
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Wind primary and secondary coils with insulation between them.
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Assemble using E-I laminations tightly.
Test:
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Use multimeter to measure secondary voltage under load
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Load = 20–30 ohm resistor
Evaluate:
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Output voltage drop must not exceed 2V
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Voltage output determines marks
굖 Important Notes:
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If transformer vibrates or explodes, it scores zero.
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Voltage outside range 12V ± tolerance a ects marks significantly.
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Keep wires tight, lamination properly arranged.
虋 General Laboratory Skills & Safety
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 Instruments You Must Know:
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Multimeter: voltage, current, resistance
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Oscilloscope: waveform visualization
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Signal generator: AC waveform source
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Breadboard: for circuit assembly
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Soldering iron: for permanent connections (if needed)
� Key Skills:
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Circuit construction from schematic
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Voltage & current measurement
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Fault-finding and debugging
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Clear labeling and waveform recording
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Self-assessment & safety compliance
蹐 Lab Safety Reminders:
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No open shoes or shorts
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Bring your own tools (breadboard, meter, wires, etc.)