Introduction to Electronics Lecture Notes

Overview of Resistors

• Definition: Resistors limit the amount of current flowing in a circuit.
• Key Formula: Ohm's Law - V = IR
  • V: Voltage (Volts)
  • I: Current (Amps)
  • R: Resistance (Ohms)

Current Calculation Example

• Battery Example:
  • 12V battery attached to a resistor.
  • Conventional Current Flow: positive terminal ➔ resistor ➔ negative terminal.
  • Electron Flow: negative terminal ➔ positive terminal.

Resistance and Current Relationship

• Increasing resistance decreases current.
• Examples:
  • 3 ohms: 12V / 3Ω = 4A
  • 6 ohms: 12V / 6Ω = 2A

Power Rating of Resistors

• Power Calculation:
  • Power (P) = Voltage (V) x Current (I)
  • Alternative Formulas:
    • P = I²R
    • P = V²/R
• Max Voltage Calculation:
  • Formula: V = √(P × R)

Example of Power Rating

• 100Ω resistor, 1.5W power rating:
  • Max voltage should be ≤ √(1.5W × 100Ω)
  • V ≈ 7.07V (to avoid overheating)

Connecting Resistors

Series vs. Parallel Connections

• Series Connection:

  • Total Resistance = R1 + R2 + ...
  • Only one path for current.

• Parallel Connection:

  • Total Resistance = 1/(1/R1 + 1/R2 + ...)
  • Multiple paths for current.

Current and Voltage in Series and Parallel Circuits

• In series: Current (I) is the same through all resistors (I1 = I2 = I3).
• In parallel: Voltage (V) is the same across all resistors (V1 = V2 = V3).

Light Bulbs and LEDs

Incandescent Light Bulbs

• Process: Incandescence - metal filament emits light when heated.
• Efficiency: Generates heat, not very efficient.

Light Emitting Diodes (LEDs)

• Efficiency: Converts electricity into light with minimal heat.
• Specifications: Typical voltage drop = 2V; current range = 0.1mA to 20mA.

Using Current Limiting Resistors with LEDs

• In a circuit with a 9V battery and 2V LED:
  • Voltage across the resistor = 7V.
  • Current limiting resistor calculation using Ohm's Law:
    • 7V / 10mA = 700Ω.

Potentiometers

• Definition: Variable resistors used to adjust resistance in a circuit.
• Applications: Brightness control in LEDs, adjustable voltage outputs.
• Example: 100k potentiometer with points A, B, C:
  • Resistance between A and C varies; total resistance remains constant.

Voltage Divider Networks

• Formula: Vout = Vin × (R2 / (R1 + R2))
• Adjusting a potentiometer in a voltage divider can change output voltage across R2.

Solar Cells

• Function: Converts light energy into electricity, used as a power source (DC).

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Additional Resources

• For more information on electronics topics, links and playlists available in the video description.
• Equipment used for circuits available through an Amazon store link.