## Glossary of ch.12 - Magnetism

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- What is symbol and units for Magnetic Flux?
- Φ , Webers (Wb)

- What is the Symbol and unit for flux density?
- B , Teslas (T)

- A magnetic field is a _____ field.
- force

- With Faraday's flux concept, the density of lines represents the _____ of the field and their direction represents the _____ of the field.
- strength, direction

- Three ferromagnetic materials are what?
- Iron, nickel, and cobalt

- The direction of a magnetic field is from ____ to ____ outside a magnet.
- North, South

- True or False. Plastic has a an effect on a magnetic field, but much smaller than iron.
- False. Plastic has no effect.

- Flux density B is defined as the ratio Φ/A, where A is the area _______ to Φ.
- Perpendicular

- To figure out the direction of the magnetic field about a current-carrying conductor, use the ____ hand rule, where your _____ points in the direction of the current.
- Right, Thumb

- Define fringing
- A decrease in flux density in an air gap between two ferromagnetic materials.

- What is the "stacking factor"?
- The ratio of ACTUAL area of ferrous material to the PHYSICAL area of the core.

- What does the symbol "H" stand for and what are it's units with respect to magnetism?
- Magnetic Field Intensity, Ampere-turns/length (At/m)

- What symbol represents Magnetomotive Force or MMF?
- £ <- supposed to be cursive F

- How are H and £ related?
- H=£/l (magnetomotive force / length)

- What happens to H (Magnetic Field Intensity) when the core's length increases?
- It decreases

- Permeability is a measure of how ____ it is to establish flux in a material.
- easy

- Define Reluctance.
- The opposition to flux in a magnetic circuit.

- How do £ (magnetomotive force), Number of turns in a coil, and I (current) relate?
- £=NI

- How do B (flux density) and H (magnetic field intensity) relate?
- B=μH where μ is permeability

- How is RMS voltage calculated for any waveform?
- squareroot of area under v squared curve divided by the base

- Why are most cheaper multimeters not accurate when calculating non-sinusoidal RMS waveforms?
- (average responding meters) They rectify AC to DC. Then take the average value and use a multiplier to calculate RMS- only works for sine waves.

- How is the effective value calculated given an AC signal added to a DC signal?
- Square root of AC squared plus DC squared. (Distance formula)

- What does j*j= ?
- -1

- What are the units for reactive power?
- VAR (volt-amps reactive)

- How do you total the power in a parallel circuit?
- By summing- same for series

- What is the symbol for Apparent Power and units?
- a. S

b. VA (volt-amps)

- How is the Power Factor calculated?
- Fp = P / S

- Define Eddy Currents.
- Unwanted current that is induced in the core of an inductor or transformer by changing core flux.

- Define Hysteresis.
- Power loss in a ferromagnetic material caused by the reversal of magnetic domains in a time varying magnetic field.