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Electricity: Circuits and their Components

An LED has a right way round

An LED is a small light with no filament. Turn a lamp round and it still glows. Turn an LED round and it stays dark.

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The idea

A new torch often has an LED for a lamp. No thin wire glows in it. It has two legs, which are thin metal wires. The long leg is +. The short leg is −.

An LED has a long leg and a short leg.
Step 1 of 4
  1. An LED has a long leg and a short leg.
  2. The long leg meets the + end. The LED glows.
  3. The wires are swapped. The LED stays dark.
  4. A filament lamp glows whichever way round it is.
The LED symbol. The triangle points the way current can flow.

An LED lets current through one way only. It glows only when its long leg meets the + end.

A teacher sets up real LEDs. Do not join one to a battery on your own.

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This track

  1. 0 Start here
  2. 1 The loop has to be unbroken
  3. 2 A switch is a gap you can close
  4. 3 Some things let the loop through
  5. 4 A drawing everyone reads the same way
  6. 5 Two or more cells make a battery
  7. 6 One loop, one break, everything stops
  8. 7 Cells are for experiments
  9. 8 Checkpoint: loops, switches, parts and safety
  10. 9 An LED has a right way round
  11. 10 Two kinds of electricity
  12. 11 Why a lamp may stay dark
  13. 12 Checkpoint: LEDs, kinds of current and faults
  14. 13 The big picture
  15. 14 Track quiz

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