# Magnetic flux density and Hall probe

• briton
In summary, the conversation is about planning an investigation on how magnetic flux density varies between opposite poles of 2 bar magnets using a Hall Probe. To do this, the speaker needs to calibrate the Hall Probe by determining the p.d. at a known magnetic field strength. The speaker initially thought of using a long straight wire with known current, but this would not work due to non-uniform magnetic field. Instead, the best approach is to use a Helmholtz coil to create a uniform field and use the formula given on Wikipedia. The speaker is seeking help and hints as they are unfamiliar with this method.
briton
I'm planning an investigation on how magnetic flux density midway between opposite poles of 2 bar magnets varies with separation of the bar magnets (using a Hall Probe). [simply as shown in attachment]

To do this, I'll need to calibrate a hall probe (which I think is done by working out the p.d. (Hall pd) at a known magnetic field strength).

My initial thoughts were that I could use a long straight wire of known current, and use $$B \ = \ \frac{\mu_0 I }{2 \pi \ r}$$
however, this would not work would it? Due to non-uniform magnetic field.

Is the best approach to use a "Helmholtz coil" to get a uniform field- and use the formula given here: http://en.wikipedia.org/wiki/Helmholtz_coils ?

I've never come across this before, so any help / hints would be appreciated. Thanks.

#### Attachments

• magflux.JPG
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gee u got this paper early

It seems like you have a solid plan for your investigation using a Hall probe to measure the magnetic flux density between two bar magnets. The Hall probe is a useful tool for measuring the strength of a magnetic field, and it is important to calibrate it properly before conducting your experiment. You are correct in thinking that a long straight wire of known current would not work due to the non-uniform magnetic field it would produce. Using a Helmholtz coil is a much better approach, as it can produce a more uniform field that will give you more accurate results. The formula you have provided from Wikipedia is a good starting point, but it is always a good idea to do some additional research and consult with your instructor or a physics expert to ensure you have the most accurate and appropriate formula for your specific experiment. Good luck with your investigation!

## 1. What is magnetic flux density?

Magnetic flux density, also known as magnetic induction or simply "B-field," is a measure of the strength of a magnetic field. It is determined by the amount of magnetic flux passing through a unit area perpendicular to the direction of the magnetic field.

## 2. How is magnetic flux density measured?

The most common method of measuring magnetic flux density is by using a Hall probe. This is a device that uses the Hall effect, which is the production of a voltage difference across an electrical conductor when it is placed in a magnetic field. The voltage produced is proportional to the strength of the magnetic field, allowing for accurate measurements of magnetic flux density.

## 3. What is a Hall probe?

A Hall probe is a small electronic device that contains a thin strip of conductive material, typically made of a semiconductor material such as gallium arsenide. When a magnetic field is applied perpendicular to the direction of current flow through the strip, a voltage is produced that can be measured and used to determine the magnetic flux density.

## 4. What is the importance of measuring magnetic flux density?

Measuring magnetic flux density is important in understanding and studying the behavior of magnets and magnetic materials. It is also crucial in many practical applications, such as in industries that use magnetic fields for manufacturing or in medical devices that utilize magnetic fields for imaging purposes.

## 5. How is magnetic flux density related to magnetic field strength?

Magnetic flux density and magnetic field strength are directly related. The higher the magnetic flux density, the stronger the magnetic field. This relationship is expressed by the equation B = μ0H, where μ0 is the permeability of free space and H is the magnetic field strength.

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