Resistance

• What does electricity involve in an electric circuit?

  A transfer of energy
• What type of energy does a cell contain?

  Chemical energy
• What is carried by the current in a circuit?

  Electrical energy
• What is the flow of electrons around the circuit called?

  Current
• What happens to electrical energy when electrons pass through a lamp?

  It is transferred to other forms of energy
• What is used to work out energy transfers in a circuit?

  Potential difference
• What does a potential difference of 9 volts across the lamp indicate?

  All electrical energy is transferred by the lamp
• What causes energy transfer in components?

  Resistance
• What does resistance tell us?

  A measure of how difficult it is for current to flow
• What happens to electrons as they move through a conductor?

  They collide with atoms
• What is transferred into other forms of energy when electrons collide with atoms?

  Electrical energy
• What is the unit for resistance?

  Ohm
• What is the equation for calculating resistance?

  Resistance = potential difference / current
• What is the resistance of lamp A with a current of 1 ampere and a potential difference of 1 volt?

  1 ohm
• What is the resistance of lamp B with a current of 1 ampere and a potential difference of 10 volts?

  10 ohms
• How do you calculate the potential difference needed to produce a certain current?

  Multiply current by resistance
• If the current is 0.5 amp and the resistance is 50 ohms, what is the potential difference?

  25 volts
• What is the relationship between potential difference, current, and resistance?

  • Potential difference (V) = Current (I) × Resistance (R)
  • Resistance (R) = Potential difference (V) / Current (I)
• What are the key concepts related to resistance in circuits?

  • Resistance indicates energy required to drive current
  • Measured in ohms
  • Higher resistance means more energy needed
• What happens to electrical energy in a circuit with resistance?

  • Electrical energy is converted to other forms
  • Examples include thermal and light energy
• How can you visualize the equation for resistance?

  • Use a triangle:
  • Top: Potential Difference (V)
  • Bottom left: Current (I)
  • Bottom right: Resistance (R)