Req Pratical: Current / PD Characteristics

• What does the investigation focus on regarding circuit components?

  How current depends on potential difference
• What is the setup for investigating a resistor's characteristics?

  • Battery connected to a resistor
  • Resistor in series with an ammeter
  • Variable resistor included
  • Voltmeter in parallel across the resistor
• What do you use to read the potential difference across the resistor?

  Voltmeter
• What do you use to read the current through the resistor?

  Ammeter
• What should 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?

  Both voltmeter and ammeter show negative values
• What does the graph of current against potential difference for a resistor look like?

  A straight line passing through zero
• What does a straight line through zero indicate about 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 if the temperature of the resistor increases?

  The graph will not have a linear shape
• What is the setup for investigating a filament lamp's characteristics?

  • Replace resistor with filament lamp
  • Adjust variable resistor
  • Record potential difference and current
  • Repeat with battery in both directions
• What does the graph for a filament lamp indicate about current and potential difference?


  Current is not proportional to potential difference
• Why does the resistance of a filament lamp increase with current?

  Because the temperature of the filament increases
• What is the setup for investigating a diode's characteristics?

  • Include a diode in the circuit
  • Add an extra resistor to protect the diode
  • Use a sensitive ammeter (milliammeter)
  • Record potential difference and current in both directions
• What happens to current when the potential difference is around 0.6 to 0.7 volts for a diode?

  Current begins to rise sharply
• What type of ammeter is used for measuring low currents in a diode circuit?

  Milliammeter
• What should you avoid to prevent overheating in the resistor during experiments?

  • Do not leave the circuit connected for too long
  • Monitor the temperature of the resistor
• What occurs when the potential difference is reversed for a diode?

  No current flows due to high resistance