current / PD characteristics

• What is the setup for investigating a resistor's current-voltage characteristics?

  • Battery connected to a resistor
  • Resistor in series with an ammeter and variable resistor
  • Voltmeter in parallel across the resistor
• How do you measure the potential difference across the resistor?

  Use the voltmeter connected in parallel
• What do you record after measuring current and potential difference?

  Values in a table
• What do you do after recording the initial readings?

  Adjust the variable resistor and record new readings
• What happens when you switch the direction of the battery?

  Potential difference direction reverses
• What does a straight line graph through zero indicate for a resistor?


  Current is directly proportional to potential difference
• What is an ohmic conductor?

  A resistor that follows Ohm's law
• What happens to the graph shape if the resistor's temperature increases?

  The graph will not have a straight line shape
• What is the procedure for investigating a filament lamp's characteristics?

  • Replace the resistor with a filament lamp
  • Adjust variable resistor and record potential difference and current
  • Repeat for both forward and reverse battery directions
• Why is the current not proportional to the potential difference in a filament lamp?

  Increased current raises the filament's temperature
• What is the effect of changing the direction of potential difference in a filament lamp experiment?

  • The graph shape remains the same
  • Current behavior is similar in both directions
• What is the setup for investigating a diode's characteristics?

  • Diode in the circuit with an extra resistor
  • Use a sensitive ammeter (milliammeter)
  • Adjust variable resistor and record readings
• What is the purpose of the extra resistor in the diode circuit?

  To protect the diode from high current
• What happens to the current when the potential difference is around 0.6 to 0.7 volts in a diode?

  Current rises sharply beyond this point
• What occurs when the potential difference is reversed in a diode?

  No current flows due to high resistance