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Art: Magnetic Fields 3 
This article is a foundation article for understanding how to reduce the strength of cell phone radiation. This article discusses the ways that a Magnetic Field can be shielded.

A common bar magnet has a Magnetic field surrounding it. A bar magnet is a Static field. It is steady. It does not change much with time. In a previous article we discussed how a changing Magnetic field can induce currents into conductors of electricity.

Magnets can only be made with materials that have basic magnetic properties. Iron is the most common of these materials. Most magnetic materials at least have some iron in them.

SHIELDING
The first way to stop, or weaken the strength of a Magnetic field is to shield with a magnetic material, such as iron. It is emphasized here that the material must be a Magnetic material. As an example, copper would be useless in shielding Magnetic fields because copper has no magnetic properties. In other words, you can't magnetize a piece of copper.

A simple shield could be a plate ( a square, a rectangle, a circle). This plate is placed between the source of the Magnetic field (like the bar magnet or an electromagnet) and whatever or whoever wants to be protected from the Magnetic field.

There are other materials used for Magnetic shielding. They are classified as Exotic because they are very effective as well as quite expensive. They include: Hypernom, Hypernic, and MuMetail.

There are quite a few important engineering considerations to take into account when specifying this magnetic shield. We will not try to cover those details here.

TWISTING
As discussed in previous article on this topic, a Magnetic field is produced anytime there is a flow of current on some conductor, such as a wire.

A magnetic field has a Direction, or we could say Polarity. When the flow of current reverses, the Direction of the Magnetic field reverses as well. If we have the same current flowing in two wires, but the currents are flowing in opposite directions, then their Magnetic fields will be opposite and to a greater or lesser extent, their Magnetic fields will cancel each other.

Let us take the simple case of a light bulb that is powered from the 60 Hz AC power line. Since this is an AC current, it is capable of inducing currents into various other conductors. In other words, the Magnetic field of the wires carrying current to the bulb, can induce currents into other conductors, or into people for that matter.

If though, we take the two wires that are running to the bulb and keep them close together, then there is a benefit, in that their Magnetic fields will cancel somewhat.

If we want to exploit this cancellation phenomenon, we would twist these two wire together. This will give us a maximum cancellation.

In future articles we will address the Electric field.