Power generation and transmission

Nature of science:

Bias: In the late 19th century Edison was a proponent of direct current electrical energy transmission while Westinghouse and Tesla favoured alternating current transmission. The so called “battle of currents” had a significant impact on today’s society. (3.5)

• Alternating current (ac) generators
• Average power and root mean square (rms) values of current and voltage
• Transformers
• Diode bridges
• Half-wave and full-wave rectification

Applications and skills:

• Explaining the operation of a basic ac generator, including the effect of changing the generator frequency
• Solving problems involving the average power in an ac circuit
• Solving problems involving step-up and step-down transformers
• Describing the use of transformers in ac electrical power distribution
• Investigating a diode bridge rectification circuit experimentally
• Qualitatively describing the effect of adding a capacitor to a diode bridge rectification circuit

Guidance:

• Calculations will be restricted to ideal transformers but students should be aware of some of the reasons why real transformers are not ideal (for example: flux leakage, joule heating, eddy current heating, magnetic hysteresis)
• Proof of the relationship between the peak and rms values will not be expected

• The ability to maintain a reliable power grid has been the aim of all governments since the widespread use of electricity started

Theory of knowledge:

• There is continued debate of the effect of electromagnetic waves on the health of humans, especially children. Is it justifiable to make use of scientific advances even if we do not know what their long-term consequences may be?

Aims:

• Aim 6: experiments could include (but are not limited to): construction of a basic ac generator; investigation of variation of input and output coils on a transformer; observing Wheatstone and Wien bridge circuits
• Aim 7: construction and observation of the adjustments made in very large electricity distribution systems are best carried out using computer-modelling software and websites
• Aim 9: power transmission is modelled using perfectly efficient systems but no such system truly exists. Although the model is imperfect, it renders the maximum power transmission. Recognition of, and accounting for, the differences between the “perfect” system and the practical system is one of the main functions of professional scientists

Data booklet reference: