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Electricity and Magnetism. Mr D. Patterson. Outcomes. explain the attraction and repulsion effects for magnets, the behaviour of freely suspended magnets and magnetic compasses, and describe the nature of the Earth's magnetic field
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Electricity and Magnetism Mr D. Patterson
Outcomes • explain the attraction and repulsion effects for magnets, the behaviour of freely suspended magnets and magnetic compasses, and describe the nature of the Earth's magnetic field • describe, using diagrams, the magnetic field in various magnetic configurations • explain that magnetic fields are associated with moving charges, and draw the field due to a current flowing through a long straight wire, a short coil and a solenoid.
Properties of Magnetism • Non contact force • North and south poles (dipoles)
Magnetic Fields • A magnetic field shows the direction the north pole of a small bar magnet will point due to the force it feels from other magnets. • Draw field lines away from north poles and toward south poles. Never cross the lines.
Magnetic flux Density • Magnetic flux density (B) is a vector quantity measuring the strength and direction of a magnetic field • It is indicated visually by the closeness of the field lines and measured using units of Teslas (T) Larger magnetic flux density Smaller magnetic flux density
The Earth is a Bar Magnet • A magnet, in the absence of any other forces will align itself with the magnetic field lines. • This is the basis for the compass.
An Electric Current Causes a Magnetic Field • E.g.: A current carrying wire • Use the right hand grip rule to determine magnetic field direction
An Electric Current Causes a Magnetic Field • E.g. Coil of wire
An Electric Current Causes a Magnetic Field • E.g. Solenoid
A Task for you • We have seen a magnetic field can be produced by an electric current. • How then, does a permanent magnet create a magnetic field?