I-V Characteristics

• What is the equation that relates voltage, current, and resistance?

  v = ir
• What does the equation v = ir represent?

  Voltage equals current times resistance
• If a circuit has a current of 4 amps and a resistance of 2 ohms, what is the voltage?

  8 volts
• How do you find resistance if you know voltage and current?

  Use r = v / i
• What is the resistance if a 24 volt battery produces a current of 8 amps?

  3 ohms
• What happens to current when voltage increases with constant resistance?

  Current increases proportionally
• What does a graph of current against potential difference show when resistance is constant?

  It shows a straight line
• What does a negative part of the current versus potential difference graph indicate?

  Voltage and current are negative
• Why do circuits with only wires or resistors have straight lines on their graphs?

  Resistance stays constant throughout
• How does the steepness of the line on a current versus potential difference graph relate to resistance?

  Less steep means higher resistance
• What happens to resistance if temperature increases?

  Resistance increases
• What is the effect of higher currents on wires over time?

  Wires heat up
• What are the characteristics of filament lamps in terms of current and resistance?

  • Filament heats up as current flows
  • Resistance increases with temperature
  • Curve gets less steep at higher currents
• How do diodes function in a circuit?

  • Allow current to flow in one direction
  • High resistance in reverse direction
  • No current flows when potential difference is negative
• What is the primary function of a diode?

  Allows current in one direction
• What happens to current in a diode when the potential difference is negative?

  No current flows
• How does the resistance of a filament lamp change with increasing current?

  Resistance increases as current increases
• What is the relationship between potential difference and current in a filament lamp?

  Less current flows per unit of potential difference