Electronics // Components // Lab
Light-emitting diodes
Topic // Why an LED needs a resistor
What this topic is
An LED lights when current flows through it one way, from the longer leg to the shorter. It needs a resistor in series so the current stays small enough not to burn it out.
Quick check
An LED is wired straight across a 5 V supply and fails at once. The learner explains why, then says what to add and where.
Ask this to see whether the topic is secure.
Topic // Mastery
What mastery looks like
What a learner can do once this topic is secure.
- Identifies the positive and negative legs of an LED and connects it the right way round
- Explains why an LED needs a series resistor
- Chooses a resistor for an LED with Ohm's law, given the supply and the LED's forward voltage and current
Topic // Map
Where this fits
What to learn first and what this topic opens up, with the reason for each link. Required links come first.
- RequiredMust come first
- HelpfulHelps, but not essential
Before this
2 topics- Complete circuitsRequired
Circuits // Ages 8 to 11
An LED only lights in a complete loop
- Ohm's lawHelpful
Circuits // Ages 12 to 15
Ohm's law picks the series resistor
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Light-emitting diodes
Ages 11 to 14 // Method
Leads to
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