Magnetic field (B-field) of a bar magnet. Magnetic field of Earth. Notice that the “North” pole of the Earth is a magnetic South pole! Earth’s field is similar to that of a bar magnet. Source of magnetic field. Magnetic fields (B-fields) are created by electrical currents.
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Notice that the “North” pole of the Earth is a magnetic South pole!
Earth’s field is similar to that of a bar magnet.
Magnetic fields (B-fields) are created by electrical currents
B = (2 10-7)I/R
The field circles or loops around an electrical current.
The direction of the field is determined by a right-hand rule.
Inside a solid material, currentswithin the atom cause each atom to act like a little magnet. In some materials, like aluminum, the atoms are not aligned, so no bar magnet. In iron, many regions (domains) of atoms are lined up magnetically and thus create a bar magnet.
A current in a wire creates a magnetic field (B-field) around the wire. If you make a coil out of the wire, the B-fields from each loop add up. You get a field around the coil that looks like that from a bar magnet!
The location of the North and South poles for the coil are determined by another right-hand rule.
When the current is on, the coil acts like a bar magnet (which end is North pole?) and attracts the real bar magnet. Where are the N and S poles for the bar?
The Earth’s magnetic field is caused by currents within molten rock. Detailed models of what is going on are still being developed.
Direction of force is determined by another right-hand rule
FB = qvB
If a current I in a wire of length L passes through the field, the force is:
FB = BIL
F = BIL
Wire can be levitated by magnetic force when a current passes through it
Caused by interaction of charged particles from Sun with Earth’s B-field and atmosphere
Planets like Jupiter and Saturn have strong B-fields that interact with charged particles from the Sun.
This is a picture of an aurora on Saturn as seen in UV light