rpa 4 - current/p.d characteristics

Cards (4)

  • current/p.d in a RESISTOR
    • directly proportional
    • ohmic conductor
    • only in temperature is constant
  • FILAMENT LAMP
    • current is not directly proportional to potential difference
    • a high current increases the temperature which increases the temperature
  • DIODE
    • we use an EXTRA RESISTOR because diodes are very easily damaged by high current
    • because we use a low current we use a sensetive ammeter called a MILLIAMMETER
    • you only get a current when the potential difference is 0.6 to 0.7 v
    • no current is produced if the potential difference is reversed because the diode has a high resistance
  • current/pd rpa in an RESISTOR , FILAMENT LAMP AND DIODE:
    1. use the VOLTMETER to read the voltage across the RESISTOR
    2. use the AMMETER to read the current through the resistor
    3. record in a table
    4. adjust VARIABLE resistor to record new readings
    5. reapeat several times
    6. switch the direction of the battery ( reverse the direction of p.d)
    7. the VOLTMETER and AMMETER will give negative readings
    8. plot on a graph