# Shielding Magnetic Fields: How Can We Measure and Contain Them?

• Piano man
In summary, using a Hall probe to measure the magnetic field between two magnets can be a useful way to determine the field strength at any point between the magnets. Additionally, using an iron box to shield the magnets will reduce the field strength at a distance.
Piano man
Hi everyone,

I have two questions related to magnetic fields.

Firstly, if I have two bar magnets with opposite poles facing each other, ie NS - NS, how do I measure the magnetic field strength at any point between the two magnets?

Secondly, how would I shield the magnetic fields of the bar magnets in a box so they are not detectable outside?

Any help would be appreciated, thanks.

Better way to prevent all the magnetic field lines from coming outside of the box is, use a box made up of a super conductor to separate bar magnets. The super conductor plate is able to divert all the field lines.

Use a "Hall Probe" (http://en.wikipedia.org/wiki/Hall_effect_sensor) to measure the magnetic field from the Bar Magnet.

To shield the magnetic field , you could use an iron box to enclose the bar magnets .
(or a thin layer of iron foil would also suffice)

hi.hms.tech I don't think a iron box can separate magnetic field lines. I have doubt about it. Can you explain?

Better way to prevent all the magnetic field lines from coming outside of the box is, use a box made up of a super conductor to separate bar magnets. The super conductor plate is able to divert all the field lines.

That sounds useful, though unfortunately I'm restricted in terms of power supply in this setup, so I need to go with the most energy efficient option and avoid a current conductor of any sort if possible.

Use a "Hall Probe" (http://en.wikipedia.org/wiki/Hall_effect_sensor) to measure the magnetic field from the Bar Magnet.

To shield the magnetic field , you could use an iron box to enclose the bar magnets .
(or a thin layer of iron foil would also suffice)

The Hall probe will be useful for measuring, though what I should have written was how do I calculate the field?

Also for the iron box shielding, how do I calculate the change in field strength across the shielding?

Thanks again.

Check out the FAQs section of Magnetic Shield Corporation's website:

https://www.magnetic-shield.com/sitemap.html

They mostly sell netic and conetic magnetic shield material and shapes, but the concepts would apply to iron shielding as well.

Thanks for that - that will be useful.
However, if I have a shield at a distance from a magnet, how do I calculate the field at that distance?
In a related question, if I have two magnets, how do I calculate the field strength at any point between them - is it merely by superposition or are there other parameters to take into account?

I would look into an advanced electrodynamics textbook, there are closed form solutions for what you need, although they will be very very complicated and require a far field approximation.

## 1. How does shielding a magnetic field work?

Shielding a magnetic field involves using materials that can redirect or absorb the magnetic field lines, preventing them from reaching the desired area. This is typically accomplished by using materials with high magnetic permeability, such as ferromagnetic materials.

## 2. What are some common materials used for shielding a magnetic field?

Ferromagnetic materials, such as iron, nickel, and cobalt, are commonly used for shielding a magnetic field. Other materials such as mu-metal, permalloy, and ferrite can also be used.

## 3. Can all magnetic fields be shielded?

No, not all magnetic fields can be shielded. It depends on the strength and frequency of the magnetic field. Some high frequency magnetic fields, such as those produced by radio waves, are difficult to shield.

## 4. What are the potential applications of shielding a magnetic field?

Shielding a magnetic field can be used in a variety of applications, such as in electronic devices to prevent interference, in MRI machines to protect the surrounding area from the strong magnetic field, and in power plants to protect workers from exposure to strong magnetic fields.

## 5. Are there any potential health risks associated with shielding a magnetic field?

There are no known health risks associated with shielding a magnetic field. However, it is important to properly shield strong magnetic fields, as they can potentially interfere with electronic devices and cause harm to individuals with pacemakers or other medical devices.

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