# How to find the magnetic flux of this magnet?

In summary, the conversation discusses finding the magnetic flux of a cylindrical magnet passing through a coil. The formula ΦB = B · A is suggested, but the magnetic field is not constant over the loop. It is clarified that the equation is asking for the cross-sectional area of the solenoid. The discussion also mentions that if the coil is not loaded, the flux in the magnet will not change and no current will flow in the coil. Finally, it is explained that the "cross section area" of the B-field will change over the loop, being expanded outside the magnet due to the spreading out of the field-curves.
I am looking to find the magnetic flux of a cylindrical magnet as it passes through a coil. I am aware of the complexity of magnetism, however, i am only looking for a conservative approximation of the magnetic flux. I found the formula ΦB = B · A, but is my understanding that the magnetic field will not be constant over the loop. How do I account for this in the calculation? Also, is the equation asking for the cross-sectional area of the solenoid, or the area of the actual piece of wire used to make the coil?

More information is needed: Is the coil loaded somehow? If not, the flux in the magnet will not change when it passes through the coil, no current will flow in the coil.
I found the formula ΦB = B · A, but is my understanding that the magnetic field will not be constant over the loop.
The magnetic flux density (B) will change over the loop, but the flux (Φ) will not. The "cross section area" of the B-field will change over the loop, being expanded outside the magnet.
is the equation asking for the cross-sectional area of the solenoid
Yes, presumably.

Hesch said:
More information is needed: Is the coil loaded somehow? If not, the flux in the magnet will not change when it passes through the coil, no current will flow in the coil.

The magnetic flux density (B) will change over the loop, but the flux (Φ) will not. The "cross section area" of the B-field will change over the loop, being expanded outside the magnet.

Yes, presumably.
Ok, I am having a hard time understanding what you mean by "the "cross section area" of the B-field will change over the loop, being expanded outside the magnet." Can you explain how this happens?

I am having a hard time understanding what you mean by "the "cross section area" of the B-field will change over the loop, being expanded outside the magnet
Actually I cannot speak of a "cross section area" as for the B-field because it is infinite. Some extremely sensitive instrument could sense your magnet field on the moon.

But this illustrates what I mean:

It is a solenoid, but it could be your magnet as well. You can see that the field-curves spread out outside the solenoid, indicating that the B-field is weaker here. Contrary the are close to each other inside the solenoid/magnet.

## 1. What is magnetic flux?

Magnetic flux is a measure of the total number of magnetic field lines that pass through a given area. It is denoted by the symbol Φ and is measured in units of webers (Wb).

## 2. How can I find the magnetic flux of a magnet?

To find the magnetic flux of a magnet, you will need a device called a fluxmeter. Place the magnet inside the fluxmeter and record the reading. This value represents the amount of magnetic flux passing through the magnet.

## 3. Does the shape of the magnet affect the magnetic flux?

Yes, the shape of the magnet can affect the magnetic flux. If the magnet has a larger surface area, it will allow more magnetic field lines to pass through, resulting in a higher magnetic flux reading.

## 4. Can the distance between the magnet and the fluxmeter affect the magnetic flux reading?

Yes, the distance between the magnet and the fluxmeter can affect the magnetic flux reading. The closer the magnet is to the fluxmeter, the more accurate the reading will be. If the distance is too far, some of the magnetic field lines may not be detected by the fluxmeter.

## 5. Is there a standard unit for measuring magnetic flux?

Yes, magnetic flux is measured in units of webers (Wb). However, smaller units such as tesla (T) and gauss (G) are also commonly used to measure magnetic flux density.

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