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Electronics from Zero · EPISODE 1 · 2:55

Voltage, Current and Resistance

Every gadget you own runs on just three ideas: voltage, current and resistance. Learn them in under 3 minutes, with simple animations — and see why one LED glows while the other burns out.

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What you'll learn

  • Voltage = the push (volts, V). A 1.5 V AA cell, a 3.7 V phone battery, 5 V USB — and the wall socket: 230 V · 50 Hz (India, UK, Europe, most of the world) or 120 V · 60 Hz (USA, Canada). Never touch it.
  • Current = the flow (amps, A). 1 A ≈ 6.24 billion billion electrons every second. It only flows in a closed loop. An LED ≈ 20 mA, a phone charging ≈ 2 A, a kettle ≈ 10 A.
  • Resistance = how hard the path fights the flow (ohms, Ω). Copper ≈ 0 Ω, rubber = huge. A 220 Ω resistor keeps an LED on 5 V at about 14 mA — take it away and the LED burns out.
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Quick refreshers

EP.01 · LED Series · 1What actually happens when you turn ON an LED? EP.09 · Electronics Basics · 1Why does a resistor resist current? EP.15 · Electronics Basics · 4AC vs DC EP.44 · Maths for Electronics · 4Power: P = V × I EP.95 · Explained SimplyWhat is electricity, really? HALF TRUE EP.96 · Myth or FactMyth or Fact: "It's the voltage that kills, not the current" EP.114 · QuizQuiz #8: Which LED leg is plus?