V = IR equation and I-V graphs

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


  v = ir
• What does the equation v = ir stand for?

  Potential difference (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 the resistance if you have a 24 volt battery producing a current of 8 amps?


  By rearranging the equation to r = v/i and calculating 24/8
• What is the resistance when using a 24 volt battery and a current of 8 amps?


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

  The current increases proportionally
• What is the relationship between voltage, current, and resistance in a circuit?


  • If resistance is constant:
  • Increasing voltage increases current
  • Decreasing voltage decreases current
• What does a graph of current against potential difference look like for circuits with only wires or resistors?


  It shows straight lines as resistance stays constant
• How does the steepness of the line on a current versus potential difference graph relate to resistance?


  A larger resistor results in a less steep line
• What does a smaller resistor require to produce a given current?


  A smaller potential difference
• What assumption is made regarding temperature when discussing resistance in circuits?


  That the temperature stays constant
• What happens to resistance when temperature increases?


  The resistance increases
• What is the function of a filament lamp?


  It emits light when current flows through a heated filament
• How does the resistance of a filament lamp change as current increases?


  The resistance increases due to heating
• What is the characteristic of diodes in terms of current flow?


  They allow current to flow in only one direction
• What happens to current in a diode when the potential difference is negative?


  No current flows due to high resistance in the reverse direction
• What are the key features of current versus potential difference graphs for different components?


  • Wires/Resistors: Straight lines, constant resistance
  • Filament Lamps: Curved lines, increasing resistance with current
  • Diodes: Current only flows in one direction, high reverse resistance