Terminology And Units For Magnetic Circuit Flashcards

1
Q

Define Magnetic circuit

A

A term that refers to the path along which the flux lines follow as they form a complete loop

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2
Q

Define the basic law for magnetic circuits

A

A magnetic flux in a circuit is directly proportional to the magnetomotive force (MMF) and inversely proportional to the reluctance of the magnetic circuit.

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3
Q

When a coil of wire has DC current flowing, it creates?

A

Millions of flux lines
1Weber (Wb) = 10^8 flux lines

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4
Q

The number of weber created by a coil is indicated by two factors.

A

1- The STRENGTH of the magnetomotive force (Fm or MMF). The value of flux is directly proportional to MMF

2- the RELUCTANCE (Rm) of the material around the coil. The value of flux is inversely proportional to the RELUCTANCE.

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5
Q

Define reluctance

A

The opposition to the setting up of magnetic lines of flux.

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6
Q

Define air gap

A

Air space or equivalent filler of non-magnetic material in the core (between the pole) of an electromagnetic coil assembly.

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7
Q

Define alloy

A

Combination of two or more elements (usually metallic) used in the manufacture of permanent magnet.

Alnico is a common alloy consisting of iron, aluminium, nickel and cobalt.

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8
Q

Define BH Curve

A

A graph which demonstrates the relationship between flux density (B) and magnetizing force (H) for an electromagnet of specific core material.

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9
Q

Define electromagnet

A

A temporary magnet constructed of a core and coil assembly which produces magnetic flux only while an electrical current flows through the coil.

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10
Q

Define ferromagnetic

A

Used to describe a material that has magnetic properties similar to iron.

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11
Q

Define flux density

A

Is the quantity of magnetic flux lines per unit area.

Unit: Tesla

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12
Q

Define Hysteresis

A

The tendency of a magnetic flux to lag behind the magnetizing force that is producing it.

Normally depicted in a graphical form called hysteresis loop.

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13
Q

Define Magnetic flux

A

The invisible lines of force that exist within any magnetic circuit.

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14
Q

Define Magnetic screen ( Shield)

A

A substance that is used to divert magnetic lines by providing an easier path for them to pass through.

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15
Q

Define magnetizing force

A

The magnetomotive force applied per unit length of a magnetic circuit.

Symbol: H
Units: Amp-turns per metre

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16
Q

Define permeability

A

A measure of the ease with which the magnetic flux can be established within a material.

Found by taking the ratio ‘B/H’

Comparable to conductivity in electrical circuit

17
Q

Define reluctance

A

The opposition that a material offers to the establishment of magnetic flux.

This is the equivalence of resistance in an electrical circuit

Symbolism: ‘S’
Unit: amper-turn per Weber

18
Q

Define residual magnetism

A

The permanent magnetism retained by a material after the magnetizing force has been removed.

19
Q

Define saturation

A

A condition where any further increased in magnetizing force does not produce any appreciable increase in magnetic flux density for an electromagnet.