V= IR Equation

• 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 while resistance remains constant?

  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 the temperature increases?

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

  Wires heat up
• What is a filament lamp?

  A light bulb with a thin metal filament
• How does a filament lamp emit light?

  By heating the filament until it glows
• What happens to resistance in a filament lamp as current increases?

  Resistance increases due to heating
• What is the function of a diode?

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

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

  • Resistors: Straight line, constant resistance
  • Filament lamps: Curved line, increasing resistance with current
• What are the differences between the behavior of resistors and diodes in circuits?

  • Resistors: Allow current flow in both directions
  • Diodes: Allow current flow in one direction only
• What factors affect the resistance in a circuit?

  • Material of the conductor
  • Length of the conductor
  • Cross-sectional area
  • Temperature
• What is the relationship between voltage, current, and resistance in a circuit?

  • Voltage (v) = Current (i) × Resistance (r)
  • As voltage increases, current increases if resistance is constant