EEE1012 Introduction to Electrical & Electronics Engineering Chapter 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:

Chapter Content Units and Formula of Magnetism Units and Formula of Electromechanical Systems

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

Magnetism Right hand grip rule:

Magnetism Right hand grip rule:

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/m 2 or T (Tesla) –Magnetic Flux Intensity: H, A/m

Magnetic Flux

Relationship: If flux density is constant

Ampere’s Law Statement: Integral of vector magnetic field intensity H around a closed path is equal to the total current inside the path 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: Integration along circular path centered at the conductor; same direction as the flux

Basic of Electromechanical Energy Conversion

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 force i = current l = conductor length B = flux density

Lorenz’s Force Law For generator action: e = Blv e = voltage v = conductor speed l = conductor length B = flux density