GCSE Physics (AQA)

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Diodes

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Electricity Current, potential difference and resistance

Diodes

6:38 Resistance of Circuit Components
Spec 4.2.1.1 4.2.1.4
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  • A diode allows current to flow in one direction only.
  • Diodes are also known as semiconductor diodes.
  • Diodes typically have a gray stripe to indicate direction.
  • Recognizing and drawing the circuit symbol for a diode is important.
  • The circuit symbol consists of a triangle and a line in a circle, indicating the diode's direction.
  • Current flows in the direction of the triangle, known as positive bias.
  • Reversing the current direction stops the flow due to the diode.
  • In exams, understanding when a current will or won't flow through a diode is necessary.
  • Conventional current flows from the positive to the negative end of a cell.
  • Diodes are useful in complex circuits to prevent reverse current flow.
  • Diodes stop current through high resistance, shown in an IV graph.
  • The threshold potential difference is where diode resistance is low, typically around 0.7 volts.
  • Above the threshold, the diode has low resistance; below it, resistance is high, stopping current.
  • Light Emitting Diodes (LEDs) light up when current flows in the correct direction.
  • LEDs are similar to diodes but emit light and have different physical indicators for direction.
  • The IV graph for LEDs is similar to standard diodes, showing low resistance above the threshold and high resistance below.

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