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# Magnetism

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by

## David Burrows

on 21 October 2014

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#### Transcript of Magnetism

Magnetism
Magnetic Forces and Fields
Magnets exert an influence over certain objects. The area of this influence is called the "
magnetic field
". It is a three-dimensional field of force as you can see from looking at the glycerin cube filled with iron filings. The shape of a magnetic field can also be seen by looking at the effect on compass needles.

The pattern of lines you see are called (surprisingly enough) "
magnetic field lines
" or lines of magnetic flux. When drawn, they typically have arrows pointing from north to south.

Magnetic field is a vector quantity and has the symbol B. It is useful to draw magnetic fields lines in such a way that their proximity to one another is significant. With this in mind we can define a term called "
magnetic flux
" as the number of lines of magnetic field passing through a given area.
Questions
Questions

Explain the difference between magnetic flux and magnetic flux density.
Calculate the magnetic flux density in a region where 2.5 × 10^–5 Wb cut through an area whose dimensions are 0.15 cm × 0.75 cm.
Draw the set of magnetic field lines surrounding the formation of magnets and rods shown.
What causes magnetism?
Individual electrons in a substance actually act like small magnets (magnetic domains). Usually their net magnetic effect is canceled out but in certain substances they all line up creating north and south poles.
The units of magnetic flux is "
Webers
" (Wb) the symbol is the Greek letter 'Phi'. B is the magnetic flux density or magnetic field strength measured in '
Teslas
'.
Example

In a uniform magnetic field, the field strength is 5.5 × 10^–4 T. If an area within the field is defined as having a length of 0.2 m and a width of 0.1 m, calculate the magnetic flux, Phi.
Full transcript