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48 Cards in this Set
- Front
- Back
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What is another name for magnetic lines of force |
Magnetic Flux |
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Magnetic lines of force never cross. T or F |
True |
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Three ways of creating magnets |
Tapping, Using DC current, stroking |
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Three ways of demagnetizing material |
Using AC current, Tapping, heat |
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What is used by watchmakers to demagnetize |
AC current |
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What is induction |
When a ferromagnetic material is brought near a magnet it magnetizes the material. |
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4 precautions to avoid damaging magnets |
Don't expose to heat, Don't place near girls created by AC Don't drop or subject to vibration Don't store magnets near magnets |
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What does reluctance mean |
A material that allows Flux lines through easily to divert away from sensitive instruments. |
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What is a natural magnet |
A permanent magnet cause from nature |
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An example of natural magnets |
Lodestone (magnetite) |
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What is artificial magnets |
Man made which doesn't depend on electrical current |
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What is Electromagnet |
Man made which doesn't depend on current flow |
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What is ferromagnets |
Metals that are easily magnetized |
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What are paramagnets |
Not easily magnetized |
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What are diamagnets |
Metals or non metals that can't be magnetized |
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Examples of ferromagnets |
Iron,nickel, cobalt |
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Examples of paramagnets |
Platinum, titanium, chromium |
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What is the best permanent magnet |
Alnico 5 |
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What is alnico 5 made from |
Aluminium copper cobalt nickel iron |
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What causes magnetism |
Static electricity charges |
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What determines the force |
Concentration of Flux lines |
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What is maximum Flux called |
Saturation |
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Using the left hand rule your thumb points where |
North |
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4 things that affect the strength of electromagnetic coils |
Distance between coils in air-core electromagnet |
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Opposition to the formation of Flux lines in the magnetic circuit is called |
Reluctance |
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Magnetomotive force |
The force that causes the setting up of Flux lines in a magnetic circuit Symbol=fm unit= A•T |
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Reluctance |
The opposition to the setting up of Flux lines Symbol=Rm unit=A•T/m |
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Flux density |
Number of lines of force per square inch Symbol=beta unit=tesla (weber per m^2) |
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Megnatizinf intensity |
The Ampere turns of the coil divided by the total length of the magnetic path in meters Symbol= H unit=A•T/m |
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Permeability |
Ability to conduct lines of Flux. Use the B-H graph Symbol=ų unit=wb/A•T•M |
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What does it mean when the material levels |
It is saturated |
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Hysteresis loop |
Is a megnatizing curve of a material plotted to show what happens to the Flux density as the force is increased, decreased and returned to zero |
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How do you control a hysteresis loop |
Vary current |
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Retentivity |
Ability to retain magnetism |
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Residual magnetism |
Amount of Flux density remaining in magnet after magnetism was removed |
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Coercive force |
Amount of magnetism force required to remove residual magnetism |
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Small loop means |
Doea not have a very large amount of residual magnetism, not a good magnet |
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Core designs have what characteristics |
High permeability and low reluctant |
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Solenoid |
When a coil is wound in a helical way for creating strong magnets |
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What's a relay |
A type of electromagnet switch |
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The spreading of Flux lines in an air gap |
Fringing |
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Coercive force |
amount of force to remove magnetism |
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Why must electrical busters be securely braced? |
Strong magnetic force occurs if there's a short |
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What is the term that refers to the Flux density of lagging behind the magnetic ingredients force. |
Hysteresis |
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Magnetic domains are considered as: |
Molecules with additive electron spins |
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Key advantage of electromagnet |
Their field strength can be varied |
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What is saturation |
Flux lines are at max value |
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How many times per second do the domains undergo a periodic reversal |
60 |
