I-V Characteristics

• IV Characteristics


  A graph which shows how the current (I) flowing through a component changes as the potential difference (V) across it is increased
• Most circuit components aren't ohmic
• Finding a component's I-V characteristic

  1. Set up test circuit

  2. Vary the variable resistor

  3. Take several pairs of readings from ammeter and voltmeter

  4. Swap over the wires connected to the battery

  5. Plot a graph of current against voltage for the component
• Linear components


  Have an I-V characteristic that's a straight line (e.g. an ohmic conductor)
• Non-linear components


  Have a curved I-V characteristic (e.g. a filament lamp or a diode)
• Ohmic conductor


  • Linear I-V characteristic
• Filament lamp


  • Curved I-V characteristic due to resistance increasing as temperature increases
• Diode


  • Current will only flow in one direction, very high resistance in reverse direction
• V = IR, so you can calculate the resistance at any point on the I-V characteristic by calculating R=V/I