Chapter Objectives and Summaries

LEARNING OBJECTIVES
Knowledge of subject matter

Define the principle of electromagnetic induction.
Apply Lenz's law to find the direction of induced current.
State Faraday's law of electromagnetic induction.
List the factors that affect the magnitude of the induced EMF in a conductor due to changing magnetic flux (B).
Perform simple calculations using the laws of electromagnetic induction, namely EMF = BLv and EMF=Ø₁-Ø₂/t
Apply a knowledge of induction principles to explain the operation of simple application devices such as microphones and generators.
State the differences between simple DC and AC generators in terms of their physical structure and output waveform.
State the principles of self induction and mutual induction as they apply to practical applications such as inductors and transformers.
Recall the equation applying to AC transformers as N1/N2 = V1/V2
List the requirements for distribution of AC electrical power in the community, explaining the advantages of power transformers

Scientific Processes

Graph and interpret the induced EMF arising from a coil rotating in a magnetic field.
Write reports on experimental and demonstration apparatus techniques used to explain electromagnetic induction principles.
Sketch and design practical application devices based on a simple EMF generator.
Classify devices that generate an EMF on the basis of armature and field designs.
Contribute to discussion and debate on the issues of electrical energy distribution and conservation.
Research extra resources for appropriate text and diagrammatic information.

Complex reasoning Processes

Solve complex problems that assemble and combine various components of electromagnetic induction and circuit laws.
Use creative thinking in analysing practical electromagnetic applications suggested.
Devise and design laboratory models that illustrate electromagnetics.
Solve complex problems using the equations of transformer and AC generator output.
Propose alternatives when discussing modern, environmentally friendly, sources of electrical power in our society.

CHAPTER 26 SUMMARY

Electromagnetic induction is the process of producing an EMF within a conductor or wire coil as a result of a changing magnetic flux.
The maximum EMF induced across a moving conductor in a magnetic field is given by (EMF=BLv)
Lenz's law states that the current induced in a conductor by a changing magnetic field is in such a direction that its own magnetic field opposes the charge that produced it.
Faraday's law of electromagnetic induction states that the EMF induced in a conductive loop is proportional to the rate of change of flux.
AC and DC generators depend on the EMF induced in a rotating armature coil within a magnetic field.
Any DC generator requires a split ring commutator assembly to allow the induced voltage to be tapped.
The peak output voltage of an alternator is given by Eo = NAB(2.Pi.f)
AC generators of commercial or industrial design are three phase machines.
A transformer is an electromagnetic device that operates on mutual induction principles to vary AC voltages.
An efficient transformer can be wired in either step up or step down mode.
Electricity authorities generate AC power using turbine driven high voltage generators and distribute the power via transformers and high voltage grids in order to overcome electrical power losses.