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Electronics from Zero · EPISODE 4 · 2:58

Series vs Parallel

Series or parallel — what really changes? Two bulbs, one battery, and the surprise that more resistors can mean LESS resistance. Learn it in under 3 minutes, with real numbers you can try.

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What you'll learn

  • Series = one path. The same current flows everywhere; the voltage is shared (two equal bulbs on 6 V get 3 V each, so both glow dimmer). One bulb breaks → everything goes dark (old Christmas lights). Resistors add: 100 + 220 = 320 Ω.
  • Parallel = side by side, each part on its own path. Every part gets the full voltage; the currents add up (1 A + 1 A = 2 A from the battery). One breaks → the others stay on. Your home is wired this way: 230 V · 50 Hz (India, UK, Europe) / 120 V · 60 Hz (USA, Canada).
  • More resistors in parallel = LESS total resistance (more paths, like opening a second door). Two equal → half: 200 Ω and 200 Ω → 100 Ω. Two different: R1 × R2 ÷ (R1 + R2).
  • Test: 6 V + two 1 kΩ resistors. Series 2,000 Ω → 3 mA. Parallel 500 Ω → 12 mA. Four times the current!
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Quick refreshers

EP.13 · Maths for Electronics · 3Series vs parallel resistors EP.26 · Home Electrical · 2Red, black, green: the 3 wires in your home EP.52 · Capacitor Series · 4Capacitors in series vs parallel EP.116 · Smart BuyerSmart Buyer #5: Power strip — what can it really handle? EP.163 · QuizQuiz #13: Two 1.5 V batteries — how do you get 3 V? → B, plus to minus