IV graphs

• Resistor:

  • A straight line on a graph going through the origin
  • Directly proportional relationship between voltage and current
  • Doubling the voltage doubles the current
  • Triple the voltage triples the current
  • Reverse voltage results in reverse current
  • True as long as at a constant temperature
• Lamp:

  • Curvy graph
  • As potential difference increases, filament gets hotter and resistance increases
  • Less current flows through as resistance increases
  • Not directly proportional
  • Curve due to filament heating up
• Diode:

  • Semiconductor component
  • Current only allowed to flow in the direction of the arrow
  • Acts like a door that needs a push to open
  • Switches on suddenly at just under a volt
  • Operational when enough potential difference is applied
  • No current flows in the opposite direction
  • Small trickle of current may flow backwards
  • Protects sensitive electronic equipment from damage
• Does current increase or decrease with more potential difference?

  Current increases with more voltage
• Why does current increase when voltage is increased?

  They are proportional
• Does an IV graph go through the origin, and why?

  An IV graph goes through the origin because with no current you have no voltage,

  
• Is an IV graph a straight line?

  An IV graph is a straight line,

  Taken the resistance stays the same

  
• Is current and voltage proportional in a filament lamp?

  Current and voltage are not proportional in a filament lamp

  
• What does the IV curve of a filament lamp look like?

  
• Why is current and voltage not proportional in a filament lamp?

  - As the current increases, the temperature in the filament in the lamp increases

  - The higher temperature makes the atoms in the metal lattice vibrate more

  - When the atoms vibrate more, it is harder for free electrons to pass-through

  
• What does it mean if the IV graph is a straight line?

  The resistance is constant
• What does a diode do?

  It allows current to flow in one direction only(Essence of rectification)

  
• What does a diode IV curve look like?

  
• What is forward bias?


  The direction in which current is allowed to flow in a diode

  
• What is reverse bias?

  The direction in which the diode does not let current through, because it has very high resistance, no current flows through

  
• How do you recognise a diode's forward bias in an IV graph?

  There is a sharp increase in voltage and current(typically on the right)

  
• How do you recognise a diode's negative bias in an IV graph?

  There is a reading of 0 current and voltage(typically on the left)

  
• What is resistance?

  The opposition to flow of current
• Does a longer length of wire have more or less resistance than a shorter piece of wire?

  A longer wire has more resistance
• How does a variable resistor work?

  By changing the length of wire that makes up the circuit therefore more or less resistance