I-V Characteristics

• What is the first step in the practical procedure?

  Set-up circuit with lamp/resistor/diode
• What should be done after altering the potential difference?

  Record the current for each p.d
• Why do you plot a graph of current against potential difference?

  To analyze the relationship between current and p.d

  
• What is the second component to be tested in the practical?

  Repeat for the other two components
• What type of meter is needed to measure potential difference?

  Voltmeter
• How should the voltmeter be connected in the circuit?

  Connected in parallel to the component
• What type of meter is needed to measure current?

  Ammeter
• How should the ammeter be connected in the circuit?

  Connected in series with the component
• What component is required to alter potential difference?

  A rheostat or variable resistor
• What is an 'Ohmic Conductor'?

  A conductor where current and p.d are proportional
• What condition must be met for a conductor to be considered Ohmic?

  Temperature must be constant
• What specific type of ammeter may be required in this experiment?

  A milliammeter
• Why might a milliammeter be required in this experiment?

  Because currents may be quite low
• What must be present in the circuit when testing the diode?

  A protective resistor
• How should the protective resistor be connected?

  Connected in series with the diode
• For which component does the polarity of the power supply matter?

  The diode
• Why does the polarity matter for the diode?

  Diodes only allow current in one direction
• What must be kept constant to get reliable results?

  Temperature should remain constant
• How can you achieve constant temperature during the experiment?

  Disconnect the supply when not taking readings
• How do you determine the resistance of a component from an I-V graph?

  Resistance is the inverse of the gradient
• What should you do to find the resistance at a given point on the graph?

  Work out the gradient and use 1/gradient
• What would you expect the I-V graph of a resistor to look like?

  A straight line through the origin

  
• What would you expect the I-V graph of a diode to look like?

  A curve that rises sharply after a threshold

  
• What would you expect the I-V graph of a filament lamp to look like?

  A curve that rises and then flattens out
• What happens to the resistance of a filament lamp as temperature increases?

  Resistance increases
• Why does resistance increase in a filament lamp with temperature?

  More energy causes more collisions with electrons