Everyday appliances

• • A moving charge transfers energy
  • Charge does work against the resistance of the circuit
• • a kettle transfers energy electrically from the mains ac supply to the thermal energy store of the heating element inside the kettle
  • energy is transferred from the battery of a handheld fan to the kinetic energy store of the fans motor
• • no appliance transfers all energy usefully
  • The higher the current, more energy transferred to the thermal energy store of the components and surroundings
• • Energy transferred = power x time
• • Power rating is the maximum amount of energy transferred between stores per second when the appliance is in use
  • This helps customers choose between models
  • The lower the power rating, the less electricity used in a given time by an appliance, so it is cheaper to run
  • An appliance may be more powerful than mother, but less efficient - might only transfer same amount of energy or less to useful stores
• • energy transferred = charge flow x potential difference
  • A battery with a higher pd will supply more energy to a circuit for every coulomb of charge