I-V characteristics

• What are the variables?

  1. Independent variable - Voltage across the circuit component being measured  
  2. Dependent variable - Current flowing through the circuit component being measured 
  3. Control variables - Temperature of the circuit
• Who is demonstrating the physics practical in the study material?

  Mr. Roots
• What is the purpose of the practical being demonstrated?

  To find the IV characteristics of different components
• What type of resistor is being used in the experiment?


  A 100 ohm resistor
• What components are being tested in the practical?

  A resistor, a filament lamp, and a diode
• Why is a variable resistor needed in the experiment?


  To adjust the resistance and measure current changes
• What is the maximum resistance of the variable resistor used?


  1 kilo ohm
• What happens if the variable resistor's resistance is too small?


  You won't get good results
• What type of power supply is mentioned for the experiment?


  A battery or a power supply that can supply up to 5 volts
• What instrument is used to measure current in the circuit?


  An ammeter
• What is the purpose of the milliamp shunt in the experiment?


  To make the ammeter more sensitive for measuring small currents
• How should the voltmeter be connected in the circuit?


  The leads from the voltmeter should piggyback across the component
• What should the readings of current and voltage be at the start of the experiment?


  Both current and voltage should be positive
• If the ammeter reads -0.06 amps, what should you do to correct it?


  Swap the leads around in the ammeter
• What is the first current reading taken in the experiment?


  0.01 amps
• What is the potential difference (PD) when the current is 0.01 amps?


  1 volt
• What does a straight line on the IV graph indicate for a fixed resistor?


  It indicates a constant resistance
• What does Ohm's law state?


  Voltage (PD) is equal to current times resistance
• What does it mean if a component is classified as an ohmic conductor?


  It has a constant resistance regardless of current and PD
• What is the behavior of the filament lamp compared to the resistor?


  The filament lamp is a non-ohmic conductor
• Why does the resistance of the filament lamp increase as the current increases?


  Because the lamp gets hotter, causing more collisions between electrons and ions
• What is the minimum voltage needed for the diode experiment?


  0.55 volts
• What happens to the current when the voltage across the diode is negative?


  The current is zero
• What does the sharp increase in gradient on the diode graph indicate?


  That the resistance has decreased to nearly zero
• What are the steps to set up the circuit for the IV characteristics experiment?


  1. Connect the battery or power supply to the variable resistor.
  2. Attach the variable resistor to the component being tested.
  3. Connect the ammeter in series with the component.
  4. Connect the voltmeter across the component.
  5. Adjust the variable resistor to change current and record readings.
• What are the differences between the IV characteristics of a resistor, filament lamp, and diode?


  • Resistor: Constant resistance, linear graph (Ohmic conductor).
  • Filament lamp: Non-linear graph, resistance increases with temperature (Non-ohmic conductor).
  • Diode: Allows current in one direction only, zero current for negative voltage.
• What is the significance of plotting an IV graph?


  • Visual representation of current vs. voltage.
  • Helps identify the type of conductor (ohmic vs. non-ohmic).
  • Allows calculation of resistance from the slope of the line.