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Glossary - P |
Paramagnetic material
Paramagnetism
Peak current meter
Permalloy
Permanent magnet
Permeability, absolute (µ)
Permeability, relative (µr)
Permeability of free space (µ0)
Permeability recoil µrec
Permeability, incremental (µΔ)
Permeability, initial (µi)
Permeameter
Permeance
Potential coil
Pulse, periodic, aperiodic
Paramagnetic material
Material having a permeability which is slightly greater than that of a vacuum, and which is approximately independent of the magnetizing force.
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Paramagnetism
Type of magnetic structure in which magnetic moments are aligned in the same direction of an external magnetic field. In absence of external field, magnetic moments are randomly oriented, so that the net result is a zero magnetization. The paramagnetism is a weak effect: 10-4 > X > 10-8
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Peak current meter
Instrument for measure the peack current of a pulse. Uses for monitoring the behaviour of a magnetizer.
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Permalloy
Fe-Ni alloy. It has soft magnetic properties, for content in Ni higher than 30 % in weight.
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Permanent magnet
See Hard magnet.
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Permeability, absolute (µ)
It is the ratio between B and H. It could be seen as an indication of the amplification of the field by the magnet. SI unit is T×m/A or H/m.
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Permeability, relative (µr)
It is the ratio between absolute permeability m and permeability of free space µ0:µr = µ/µ0. It is dimensionless. Magnetic material could be distinguished by their relative permeability: µr < 1 for diamagnetic materials, µr > 1 for paramagnetic materials, µr >> 1 for ferromagnetic materials. The relative permeability of some alloys arrives up to 105.
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Permeability of free space (µ0)
The permeability of free space (vacuum) is 1.256×10-6 H/m.
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Permeability recoil µ
recIs the average slope of a minor hysteresis loop.
For permanent magnets, it is about 1.05 ÷ 1.15.
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Permeability, incremental (µΔ)
It is the ratio of the cyclic change of B to the corresponding cyclinc change of H in a specified static field H:
1 ΔB
µΔ = ____ . ____
µ0 ΔH
The limiting value of µΔ for ΔH → 0 is the reversible permeability (see).
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Permeability, initial (µi)
The slope of the normal magnetization curve at zero magnetizing force.
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Permeameter
Instrument to measure hysteresis loop, normal magnetization and permeability of soft magnetic materials. It consists of an electromagnetic yoke, power supply, fluxmeter, gaussmeter and measuring coils.
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Permeance
It is the inverse of the reluctance (see).
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Potential coil
Coil to measure the potential difference of H between two points. It is useful to determine the H of the working point of a permanent magnet.
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Pulse, periodic, aperiodic
Different behaviours of a magnetiser. The mode of operation is imposed by either the magnetiser internal power circuit and the parameters of the magnetiser discharging circuit with the magnetising coil.
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