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// FREE MINI-COURSE · Ω

Electronics Basics

Core Components, Visually — Resistors, dividers and the laws behind every circuit.

11 of 12 lessons out · next: The 555 timer: one chip that blinks

▶ Start lesson 1
  1. 01 Why does a resistor resist current?Electrons collide with atoms and lose energy as heat; Ohm's law V = I × R. EP.09 · 20 s
  2. 02 Voltage divider — create a voltage with mathVout = Vin × R2 ÷ (R1 + R2): make 2.5 V from 5 V with two resistors. EP.08 · 20 s
  3. 03 Series vs parallel resistorsHow resistances add up in series and divide in parallel. EP.13 · 20 s also in Maths for Electronics
  4. 04 AC vs DCDC flows one way (battery, USB 5 V); AC swings back and forth 50 times a second (230 V wall socket); a charger turns AC into DC. EP.15 · 20 s
  5. 05 How a transformer worksTwo coils on an iron core: AC makes a changing magnetic field that makes voltage in coil 2; turns set the volts (Vout = Vin × Ns ÷ Np, 230 V → 12 V), and DC gives 0 V out. EP.17 · 20 s
  6. 06 AC → DC: how a power supply makes DCA diode lets current pass one way only (~0.7 V drop); a transformer, 4-diode bridge, capacitor and 7805 regulator turn 230 V AC into a steady 5 V DC. EP.24 · 20 s
  7. 07 The DIODE: the one-way valve that turns AC into DCInside a diode P meets N with a barrier: forward it conducts (~0.7 V drop), reversed it blocks; 1 diode = half-wave, a 4-diode bridge = full-wave; the silver band is the cathode. EP.32 · 20 s
  8. 08 The TRANSISTOR: a tiny current switches a BIG oneA tiny base current (4.3 mA from an Arduino pin) switches a big collector current (100 mA, 12 V lamp) — C/B/E legs, N-P-N inside, always a base resistor + shared GND. EP.37 · 20 s
  9. 09 The RELAY: 5 V switches 230 VA 5 V coil becomes a magnet and pulls the arm (COM: NC → NO) to switch a separate 230 V circuit; a transistor drives the 71 mA coil from an Arduino pin, and a flyback diode across the coil eats the turn-off spike. EP.38 · 24 s
  10. 10 The MOSFET: big DC loads, no clickA logic-level MOSFET (G/D/S) lets a 5 V pin switch amps of DC silently; gate resistor + pull-down, vs relay and BJT. EP.39 · 24 s
  11. 11 The inductor: the coil that fights changeWhy the current in a coil can't jump (it stores energy in a magnetic field), where the relay's turn-off spike comes from, and how inductors smooth current. EP.73 · 24 s