RP I-V Characteristics

• Investigating the current-voltage characteristics of circuit components

  1. Use a voltmeter to read the potential difference across the component

  2. Use an ammeter to read the current through the component

  3. Record the potential difference and current values in a table

  4. Adjust the variable resistor to get a range of readings

  5. Reverse the direction of the battery and record the new readings
• For a resistor


  Current is directly proportional to potential difference
• The graph of current vs potential difference for a resistor is a straight line passing through the origin
• A resistor is an ohmic conductor
• If the temperature of the resistor increases, the graph will not be a straight line
• For a filament lamp


  Current is not proportional to potential difference
• As current increases, the temperature of the filament lamp increases, causing the resistance to increase
• The graph of current vs potential difference for a filament lamp has the same shape when the direction of the potential difference is reversed
• Investigating the current-voltage characteristics of a diode

  1. Use a milliammeter to measure the low current

  2. Include an extra resistor to protect the diode from high current

  3. Adjust the variable resistor to get a range of readings

  4. Record the potential difference and current values in a table

  5. Reverse the direction of the battery and record the new readings
• For a diode, current only flows when the potential difference is around 0.6-0.7 V
• For a diode, there is no current if the potential difference is reversed
• Diodes have a high resistance in the reverse direction