V=IR equations and I-V graphs

• 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 have a voltage of 24 volts and a current of 8 amps?


  r = v / i
• What is the resistance when the voltage is 24 volts and the current is 8 amps?

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

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

  It shows straight lines
• What does a steeper line on a current versus potential difference graph indicate?

  Less resistance in the circuit
• What happens to the resistance if the temperature increases in a circuit?

  Resistance increases
• Why do filament lamps have a less steep curve as current increases?

  Resistance increases due to heating
• What do diodes allow in terms of current flow?

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

  No current flows
• What are the key characteristics of filament lamps and diodes?

  • Filament lamps:
  • Contain a thin metal filament
  • Emit light when heated
  • Resistance increases with current

  
  

  • Diodes:
  • Allow current in one direction
  • High resistance in reverse direction
  • No current flows when potential difference is negative