So, in an electric field the direction is away or towards the source of the field because if you put a charge in the field, the charge will move away or towards source.
In a magnetic field, though, I can’t see what “north to south” means, or why the induction lines on a magnet are circular and have a direction.
If the direction is north to south, shouldn’t it mean that something in the north pole will move itself to the south pole? Also, if we put a metal close to a magnet it would be attracted towards it, so shouldn’t the direction of the field be towards the magnetic source, like in a electric field?
In: Physics
The simplest example of this is a compass. If a bar magnet is placed on a low friction balance set up, or floated in a dish of water, it will gradually align itself in the direction of the Earth’s magnetic field.
Actually, if you use a set of 3-d gimbals to suspend the magnet, you’ll find that the the direction of Earth’s magnetic field actually points up out of the ground except near the equator. It doesn’t run parallel to the ground like a standard compass might suggest.
This is all to say that an external magnetic field will exert a net torque on a magnet that works to orient the poles of the magnet parallel to the direction of the magnetic field.
Another example is placing a sheet of paper on top of a magnet and then sprinkling iron filings onto the sheet. The filings will tend to stick together in the direction of the field, forming linear structures.
This gives good evidence that a magnetic field is not isotropic, meaning it is not equal in any direction. Rather, it’s effects depend on direction.
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