## Chapter Objectives and Summaries

### CHAPTER 26 Electromagnetic Induction

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=Ø12/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.