P2- IV characteristics

• Outline the basic steps of the practical

  1. Set-up circuit with lamp/resistor/diode

  2. Alter the potential difference in regular increments

  3. Record the current for each p.d

  4. Plot a graph of current against p.d

  5. Repeat for the other two components
• Voltmeter


  Connected in parallel to the component
• Ammeter

  Connected in series with the component
• Rheostat


  Variable resistor used to alter potential difference if not using a variable power pack
• Ohmic Conductor


  • A conductor for which current and potential difference are directly proportional
  • Resistance remains constant as current changes
  • Temperature must be constant
• Milliammeter

  Specific type of ammeter required in this experiment due to low currents and current changes involved
• Protective resistor


  Must be present in the circuit when testing the diode, connected in series with the diode to prevent too high current levels
• Diode


  Polarity of power supply matters as diodes only allow current to flow in one direction
• Temperature

  Must be kept constant to get reliable results, can be achieved by disconnecting supply when not taking readings to avoid unnecessary heating
• Resistance from I-V graph


  Inverse of the gradient of the line drawn from a point on the graph to the origin
• 1. V graph of a resistor


  • Linear, straight line through origin
• 1. V graph of a diode


  • Asymmetric, steep gradient in one direction, flat in the other
• 1. V graph of a filament lamp

  • Curved, increasing gradient as current increases
• Resistance of filament lamp

  Increases as temperature increases, due to increased vibration of ions causing more collisions with electrons