11. Electromagnetic induction

11. Electromagnetic induction

11.1 – Electromagnetic induction

Nature of science:

• Experimentation: In 1831 Michael Faraday, using primitive equipment, observed a minute pulse of current in one coil of wire only when the current in a second coil of wire was switched on or off but nothing while a constant current was established. Faraday’s observation of these small transient currents led him to perform experiments that led to his law of electromagnetic induction.

Understandings:

• Emf

• Magnetic flux and magnetic flux linkage

• Faraday’s law of induction

• Lenz’s law

Applications and skills:

• Describing the production of an induced emf by a changing magnetic flux and within a uniform magnetic field

• Solving problems involving magnetic flux, magnetic flux linkage and Faraday’s law

• Explaining Lenz’s law through the conservation of energy

11.2 – 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.

Understandings:

• 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

11.3 – Capacitance

Nature of science:

• Relationships: Examples of exponential growth and decay pervade the whole of science. It is a clear example of the way that scientists use mathematics to model reality. This topic can be used to create links between physics topics but also to uses in chemistry, biology, medicine and economics.

Understandings:

• Capacitance

• Dielectric materials

• Capacitors in series and parallel

• Resistor-capacitor (RC) series circuits

• Time constant

Applications and skills:

• Describing the effect of different dielectric materials on capacitance

• Solving problems involving parallel-plate capacitors

• Investigating combinations of capacitors in series or parallel circuits

• Determining the energy stored in a charged capacitor

• Describing the nature of the exponential discharge of a capacitor

• Solving problems involving the discharge of a capacitor through a fixed resistor

• Solving problems involving the time constant of an RC circuit for charge, voltage and current