V=IR & I-R

• 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
• What is the formula to calculate resistance from voltage and current?


  r = v / i
• What happens to current when voltage increases while resistance remains constant?


  The current increases proportionally
• What does a graph of current against potential difference look like for circuits with constant resistance?


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


  A smaller resistor is present
• If a circuit contains a 10 ohm resistor, how does the line on the graph compare to a circuit with a smaller resistor?


  The line would be less steep
• What assumption is made regarding temperature when discussing resistance in circuits?


  That the temperature stays constant
• What effect does increasing temperature have on resistance?


  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 a diode in terms of current flow?


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


  No current flows
• How does the resistance of a diode behave in the reverse direction?


  It has a very high resistance
• What are the key features of current versus potential difference graphs for different components?


  • Straight lines for resistors with constant resistance
  • Steeper lines for smaller resistors
  • Less steep lines for larger resistors
  • Curved lines for filament lamps due to increasing resistance with temperature
  • Diodes only show current with positive potential difference