P3.4 V=IR & 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 using a 24 volt battery producing 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?

  A smaller resistor is present
• What happens to the resistance if the temperature increases in a circuit?

  Resistance increases
• Why do filament lamps have a less steep curve at higher currents?

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

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

  No current flows
• What are the characteristics of current versus potential difference graphs for resistors and wires?

  • Straight lines indicate constant resistance
  • Steeper lines indicate smaller resistors
  • Less steep lines indicate larger resistors
• What are the effects of temperature on resistance in electrical circuits?

  • Increased temperature raises resistance
  • Higher currents can heat wires
  • Resistance may not remain constant
• What are the differences between filament lamps and diodes in terms of current flow?

  • Filament lamps: resistance increases with current
  • Diodes: allow current in one direction only