Magnetic shielding may seem like the stuff of science fiction novels and movies, but it’s real. Unlike some forces, such as electricity, magnetic fields can’t technically be blocked. This is because there is no monopole magnet--or at least not one that we know. The magnetic field lines run from a magnet’s north and south pole, which makes blocking them difficult.

What is Magnetic Shielding?

Magnetic field lines are an invisible force that exist in all magnets and even on the Earth--the planet is actually similar to a bar magnet, with lines running from the magnetic north to the magnetic south pole. Since they are a natural occurrence, even if you place a thick non-magnetic object between two strong rare earth magnets, the magnetic field isn’t necessarily blocked. The lines just go around the object. However, it doesn’t mean that the magnets will still be attracted to each other. You can try blocking magnetic fields and test the results with this quick experiment.

Supplies

  • Two strong magnets
  • Piece of paper
  • Sheet of magnetic metal (steel)

Steps

  1. Place the sheet of metal vertically. You may want to create a holding standing, so that it stays upright and in place.
  2. Take your two strong magnets and place them on each side of the sheet, opposite from another. Take note of what happens.
  3. Do the same with a sheet of paper. Place it standing upright. You may need to hang it from a clip or string. Then, place the magnets on each side.
The magnets should stick to the object in the middle in each case, but for different reasons. For one, the paper is non-magnetic and thin, so it doesn’t do an effective job of blocking the magnetic attraction. The magnets stick to the sheet of metal, because it is a magnetic object. However, ferromagnetic materials are used in order to shield, or redirect, magnetic fields. The thickness of the material used plays a part. The thicker the object blocking it is, the more resistance to the magnetic field. Even though magnetic shielding isn’t quite blocking, there are specially made materials used for it. For example, mu-metal--an alloy of iron, nickel, chromium and copper--are commonly used. Magnetic shielding is essential for electronics that use magnets in order to function, which is most of the technology and devices that we use today such as: TVs, speakers, MRI rooms and more.