Homework 7 Flashcards
In what units are the solutions for equation 20.3?
Tesla
two sources of magnetic moments for electrons
electron’s orbital motion
around the nucleus, and also, its spin
Do all electrons have a net magnetic moment?
Each electron will have a net magnetic moment from spin, and possibly, orbital
contributions, which do not cancel for an isolated atom
Do all atoms have a net magnetic moment
All atoms do not have a net magnetic moment. If an atom has completely filled
electron shells or subshells, there will be a cancellation of both orbital and spin magnetic
moments.
is the material ferromagnetic if the susceptibility (X_m) value is much larger than values on table 20.2 for diagmagnetics and paramagnetics?
True
why can ferromagnetic materials be permanently magnetized whereas paramagnetic ones cannot
because of the ability of net spin magnetic moments of adjacent atoms to align with one
another.
For paramagnetic materials, there is no magnetic dipole coupling, and, consequently,
domains do not form. When a magnetic field is removed, the atomic dipoles assume random
orientations, and no magnetic moment remains
why does the magnitude of the saturation magnetization decreases with increasing temperature for ferromagnetic materials, and why does ferromagnetic behavior ceases above the Curie temperature
ferromagnetic materials-the atomic thermal vibrational motions counteract the coupling forces
between the adjacent atomic dipole moments, causing some magnetic dipole misalignment
Curie temperature because the atomic thermal
vibrations are sufficiently violent so as to completely destroy the mutual spin coupling forces
Explain magnetic hysteresis and why it occurs for ferro- and ferrimagnetic materials
Magnetic hysteresis occurs when the flux falls behind the magnetic field. It occurs in these materials because their flux density is much greater than paramagnetic or diamagnetic materials.
On a B-H Curve where is Saturation?
Top Right
What are the differences between hard and soft magnetic materials in terms of both hysteresis
behavior and typical applications
hard magnetic material has a high remanence, a high coercivity, a high saturation flux density, high hysteresis energy losses, and a low initial
permeability such as motors (permanent magnet motors), audio and video recorders, hearing aids, and computer
peripherals
soft magnetic material, has a high initial permeability, a low coercivity, and low hysteresis energy losses.alternating and when energy
losses must be low—such as transformer cores, generators, motors (electromagnet), and
switching circuits
how do you find saturation magnetization from B-H Curve?
Eq. 20.8 Solve for M
How do you find remanence from B-H curve?
When H=0 (@ y axis) should be less than saturation.
How do you find coercivity from B-H curve?
When B=0 (@ x axis)
How would you classify this material as a soft
or hard magnetic material?
By comparing tables on soft and hard materials. Or find the area in the curve and use hysteresis loss/cycle comparison.
