Lecture 1 - Magnetism Flashcards
What is the property of certain substances or phenomena that give rise to magnetic fields?
Magnetomotive force
MMF
The magnetomotive force (mmf) is also known as?
Magnetic potential
What is H
Magnetic field intensity
Units: A/m
What is U?
Magnetomotive force or ampere turns
Units: At
What is B?
Flux density
Units: T (Tesla)
What is Φ?
Flux in a component
Units: Wb (Weber)
What is the value of the permeability constant, mu?
4pi10^-7 H/m
In B-H curves, if the knee point is exceeded what occurs?
Saturation will occur
Air gap length is usually selected so that required mechanical clearance is established while given the highest possible…
Flux density level
The induced voltage is proportional to what?
Proportional to the rate of change of flux
What does Faraday’s first law of electromagnetic induction state?
Any change in the magnetic field of a coil of wire will cause an emf to be induced in the coil
What does Faraday’s second law of electromagnetic induction state?
The magnitude of emf induced in the coil is equal to the rate of change of flux linkages ( flux linkages is the product of turns of the coil and the flux associate with it)
What does Lenz’s law state?
It states that the current caused by the induced voltage in a circuit will flow in such a direction that opposes the change of flux
What is residual flux?
When large magnetomotive force is applied to the core then removed. The flux in the core doesn’t return to zero, instead a magnetic field is left behind in the core
How do Hysteresis losses occur?
The magnetic material absorbs energy during each cycle and energy is dissipated as heat
