How are fields used to move electrical energy?

The production, distribution and use of electricity has had a major impact on human lifestyles. In this area of study students use empirical evidence and models of electric, magnetic and electromagnetic effects to explain how electricity is produced and delivered to homes. They explore magnetic fields and the transformer as critical to the performance of electrical distribution systems.

On completion of this unit the student should be able to analyse and evaluate an electricity generation and distribution system.

Key knowledge

Generation of electricity

  • calculate magnetic flux when the magnetic field is perpendicular to the area, and describe the qualitative effect of differing angles between the area and the field: \phi_B=B_\perp A
  • investigate and analyse theoretically and practically the generation of electromotive force (emf) including:
    AC voltage and calculations using induced emf: \varepsilon=-N\frac{\Delta\phi_B }{\Delta t}, with reference to:
    – rate of change of magnetic flux
    – number of loops through which the flux passes
    – direction of induced emf in a coil
  • explain the production of DC voltage in DC generators and AC voltage in alternators, including the use of split ring commutators and slip rings respectively.

Transmission of electricity

  • compare sinusoidal AC voltages produced as a result of the uniform rotation of a loop in a constant magnetic field with reference to frequency, period, amplitude, peak-to-peak voltage (V_{p-p} ) and peak-to-peak current (I_{p-p} )
  • compare alternating voltage expressed as the root-mean-square (rms) to a constant DC voltage developing the same power in a resistive component
  • convert between rms, peak and peak-to-peak values of voltage and current
  • analyse transformer action with reference to electromagnetic induction for an ideal transformer: \frac{N_1}{N_2}=\frac{V_1}{V_2}=\frac{I_2}{I_1}
  • analyse the supply of power by considering transmission losses across transmission lines
  • identify the advantage of the use of AC power as a domestic power supply.



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