Magnetic Circuits and Hysteresis Flashcards

Vocabulary flashcards defining core terms, material classifications, principles, and concepts related to magnetic circuits and hysteresis.

Generator Working Principle

Whenever flux linking a conductor changes, an electromotive force (emf) is induced.

Motor Working Principle

Whenever a current-carrying conductor is placed in a magnetic field, torque is produced.

Magnetic Circuit

A closed path or loop through which magnetic flux flows, analogous to an electric circuit but dealing with magnetic fields instead of electric currents.

Magnetic Flux ($\Phi$)

The total magnetic field passing through a circuit, measured in Weber ($\text{Wb}$).

Magnetomotive Force (MMF)

The work done to move a unit magnetic flux once around a magnetic circuit, analogous to electromotive force (EMF) in electric circuits, measured in Ampere-turns ($\text{AT}$).

Reluctance ($S$)

The opposition offered by the material of a magnetic circuit to the flow of magnetic flux, measured in Ampere-turns per Weber ($\text{AT/Wb}$).

Magnetic Permeability ($\mu$)

The ability of a material to allow the flow of magnetic flux around a magnetic circuit.

Magnetic Flux Density ($B$)

The number of magnetic lines passing over a specified area, calculated as $B = \frac{\Phi}{A}$ and measured in Tesla ($\text{T}$) or Weber per square meter ($\text{Wb/m}^2$).

Relative Permeability ($\mu_r$)

The ratio of the permeability of a medium to the permeability of air, given by $\mu_r = \frac{\mu_{\text{medium}}}{\mu_{\text{air}}}$.

Ferromagnetic Materials

Materials that have a relative permeability much greater than 1 ($\mu_r \gg 1$), such as iron and cobalt.

Paramagnetic Materials

Materials that have a relative permeability slightly greater than 1 ($\mu_r > 1$), such as platinum and nickel.

Diamagnetic Materials

Materials that have a relative permeability less than 1 ($\mu_r < 1$), such as gold and water.

Soft Ferromagnetic Materials

Ferromagnetic materials that can be magnetized but do not stay magnetized, used to make temporary magnets (e.g., iron).

Hard Ferromagnetic Materials

Ferromagnetic materials that can be magnetized and stay magnetized, used to make permanent magnets (e.g., steel).

Ampere's Work Law

States that the work done in moving a unit magnetic pole once around a magnetic circuit is equal to the Ampere-turns ($N \times I$) enclosed by the circuit.

Magnetizing Force ($H$)

The magnetic field intensity per unit length of the magnetic path, calculated as $H = \frac{N \times I}{l}$ and measured in Ampere-turns per meter ($\text{AT/m}$).

Ohm's Law of Magnetic Circuit

The relationship stating that Magnetomotive Force equals Magnetic Flux multiplied by Reluctance ($\text{MMF} = \Phi \times S$).

Leakage Factor (L.F.)

The ratio of total flux produced to the useful air-gap flux, given by $\text{L.F.} = \frac{\Phi_{\text{total}}}{\Phi_{\text{gap}}}$.

Hysteresis Loop

A graphical loop showing the relationship between magnetic flux density ($B$) and magnetizing field strength ($H$) during a complete cycle of magnetization.

Saturation Point

The maximum value of magnetic flux density ($B$) that a magnetic material can achieve under an external magnetic field ($H$).

Retentivity

The value of residual magnetic flux density ($B$) that remains in a magnetic material when the magnetizing field intensity ($H$) is reduced to zero.

Coercivity

The magnitude of magnetic field strength ($H$) required to reduce the magnetic flux density ($B$) to zero after a material has been magnetized.

Hysteresis Energy Loss

The energy spent per unit volume of iron core per cycle of magnetization, which is equal to the area enclosed by the hysteresis loop ($W = \oint H \, dB$).