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Components & Their Functions

Resistors

Function: Limit current flow and reduce voltage

  • Non-polarized: Can be connected either way
  • Common values: 100Ω, 220Ω, 470Ω, 1kΩ, 10kΩ (E12/E24 series)
  • Power rating: 1/4W (0.25W) is most common for small circuits
Key uses:
  • Limiting current to LEDs and sensitive components
  • Creating voltage dividers
  • Pull-up/pull-down resistors for digital circuits
LEDs (Light Emitting Diodes)

Function: Emit light when current flows through them

  • Polarized: Longer leg is positive (anode), shorter leg is negative (cathode)
  • Forward voltage: Red ~1.8V, Green ~2.0V, Blue ~3.0V, White ~3.2V
  • Typical current: 20mA maximum, 10-15mA recommended
Warning: LEDs MUST have a current-limiting resistor! Without one, they draw too much current and burn out instantly.
Example calculation: For a red LED with 5V supply:

R = (5V - 1.8V) / 0.02A = 160Ω

Diodes

Function: Allow current to flow in only one direction

  • Polarized: Anode (positive) to Cathode (negative with stripe)
  • Forward voltage drop: ~0.7V for silicon, ~0.3V for Schottky
  • Blocks reverse current: Acts like an open circuit when reversed
Types:
  • Standard (1N4007): General purpose rectification, 0.7V drop
  • Schottky: Low voltage drop (0.3V), fast switching
  • Zener: Voltage regulation, conducts in reverse at specific voltage
Capacitors

Function: Store and release electrical energy

  • Measured in: Farads (usually microfarads μF or picofarads pF)
  • Some are polarized: Electrolytic capacitors have + and - markings
  • Ceramic capacitors: Non-polarized, small values (pF to nF)
Key uses:
  • Smoothing power supplies (filtering)
  • Coupling AC signals while blocking DC
  • Timing circuits with resistors (RC circuits)
Switches & Buttons

Function: Control current flow by opening/closing the circuit

  • Non-polarized: Can be connected either way
  • Toggle switch: Stays in position (on/off)
  • Momentary button: Only makes contact while pressed (tactile switch)
States:
  • Closed (ON): Acts like a wire, current flows freely (very low resistance)
  • Open (OFF): Acts like a break, no current flows (infinite resistance)
Circuit Breakers & Fuses

Function: Protect circuits from excessive current

  • Non-polarized: Can be connected either way
  • Current rating: Specified in Amps (e.g., 100mA, 500mA, 1A, 5A)
Differences:
  • Circuit Breaker: Trips when current exceeds rating, can be reset and reused
  • Fuse: Blows (melts) when current exceeds rating, must be replaced
Safety tip: Always use breakers/fuses in circuits with power sources to prevent dangerous overheating and fire hazards!
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