EEE1012 Introduction to Electrical & Electronics Engineering Chapter 8: Magnetism by Muhazam...
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Transcript of EEE1012 Introduction to Electrical & Electronics Engineering Chapter 8: Magnetism by Muhazam...
EEE1012Introduction to Electrical &
Electronics EngineeringChapter 8: Magnetism
by Muhazam Mustapha, October 2010
Learning Outcome
• Be able to utilize and understand the concepts and formula of magnetism
• Be able to utilize and understand some of the processes and formula of electromechanics
By the end of this chapter students are expected to:
Magnetism
• Magnetism is a phenomenon that comes alongside electrodynamic phenomenon
• Moving electrons are known to have spin that is theoretized to cause magnetism
• The current (opposite of electron) flow causes magnetic field to form circularly according to right hand grip– Current is in thumb direction– Magnetic field direction is the fingers direction
Magnetic Flux
• Magnetic flux is the imaginary entity that is considered to form magnetism
• The direction of magnetic flux is the direction of compass aligned with the flux (from magnetic north pole to south pole)
• Units and symbols:– Magnetic Flux: Ф, Wb (Weber)– Magnetic Flux Density: B, Wb/m2 or T (Tesla)– Magnetic Flux Intensity: H, A/m
Ampere’s Law
Statement:
Integral of vector magnetic field intensity H around a closed path is equal to the
total current inside the path
id lH iHdl If the direction of the closed loop is the same as the field direction
Ampere’s Law
• For a single conductor flowing a current of i, this reduces to:
r
iH
2
Integration along circular path centered at the conductor; same direction as the flux
Lorenz’s Force Law
• For motor action:
f = il×B
• If the vectors l and B are perpendicular,
f = Bli
• Right hand rule:Force
Current
Flux
f = mechanical forcei = currentl = conductor lengthB = flux density