Motors & Generators

  • solve problems using F l =k i 1 i 1 d
  • - perform a first-hand investigation to demonstrate the motor effect
  • solve problems and analyse information about the force on current-carrying conductors in magnetic fields using: F=BIlsin θ
  • solve problems and analyse information about simple motors using: τ =nBIAcos θ
  • solve problems and analyse information about simple motors using:
9.3.2The relative motion between a conductor and magnetic field is used to generate an electrical voltage
  • outline Michael Faraday’s discovery of the generation of an electric current by a moving magnet
  • - define magnetic field strength B as magnetic flux density
  • describe the concept of magnetic flux in terms of magnetic flux density and surface area
  • generated potential difference as the rate of change of magnetic flux through a circuit
  • account for Lenz’s Law in terms of conservation of energy and relate it to the production of back emf in motors
  • explain that, in electric motors, back emf opposes the supply emf
  • explain the production of eddy currents in terms of Lenz’s Law
9.3.3 Generators are used to provide large scale power production
9.3.4 Transformers allow generated voltage to be either increased or decreased before it is used
  • describe the purpose of transformers in electrical circuits
  • compare step-up and step-down transformers
  • identify the relationship between the ratio of the number of turns in the primary and secondary coils and the ratio of primary to secondary voltage
  • explain why voltage transformations are related to conservation of energyfrom the generator to the consumer
  • - explain the role of transformers in electricity sub-stations
  • - discuss why some electrical appliances in the home that are connected to the mains domestic power supply use a transformer
  • - discuss the impact of the development of transformers on society
  • perform an investigation to model the structure of a transformer to demonstrate how secondary voltage is produced
  • solve problems and analyse information about transformers using: V p V s = n p n s
  • gather, analyse and use available evidence to discuss how difficulties of heating caused by eddy currents in transformers may be overcome
  • gather and analyse secondary information to discuss the need for transformers in the transfer of electrical energy from a power station to its point of use
9.3.5 Motors are used in industries and the home usually to convert electrical energy into more useful forms of energy
  • describe the main features of an AC electric motor
  • perform an investigation to demonstrate the principle of an AC induction motor
  • gather, process and analyse information to identify some of the energy transfers and transformations involving the conversion of electrical energy into more useful forms in the home and industry