# Magnetic Flux Density: B, \phi, H - True or False?

• unseensoul
In summary, magnetic flux density and magnetic flux are two different quantities denoted by the symbols B and \phi, respectively. Magnetic field strength, denoted by H, is related to magnetic flux density but not the same. The terminology surrounding magnetism can be ambiguous, so it is best to use the universal symbols B and H instead of words.
unseensoul
magnetic flux density is denoted by the B symbol
magnetic flux is denoted by the $$\phi$$ symbol

so why do people use B as if they were referencing to magnetic flux?

"magnetic flux density is a measurable quantity indicating the strength of a field" ...this was stated by a teacher of mine...anyway, is true?

First, magnetic flux density isn't it the same as magnetic induction, i.e. magnetic flux per unit area perpendicular to the magnetic field?
Second, I thought that the strength of a field was denoted by H...

I've been searching throughout the internet and I found different meanings for the same thing which lead me to get more confused.

Best regards
-unseensoul

Here's a good start
http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.html

Just remember that, at a practical level, the magnetic field strength H is most useful when dealing with magnetic materials (soft iron, silicon steel, etc.).

If you just want a memory trick (not completely true), think of H as the cause and B as the result.

I'm sorry to give a 75% answer (i.e., not absolutely true), but I can't think of anyway short of about three hours to say it all. Perhaps another responder will have a more succinct answer.

I've taken a look to it before I came here and it didn't help me :\

ps: I'm sorry to get you back so late...

B is magnetic flux density - keyword: density. As in, magnetic flux per unit area/volume. Phi is the total amount, i.e. in the same way that density * volume = mass.

Referring it to as magnetic flux is probably just a short hand way of going about things.

I didn't mean that. What I'd like to know is why is the magnetic flux density referred as the magnetic field strength?

Thank you

Magnetic field strength is not the same as the magnetic flux density. They are proportional (the constant (?) of proportionality being permeability). If some source refers to them as the same, that source is incorrect.

The words describing magnetism can be ambiguous and vary over time.
It is best to use B and H instead of words, because the usages B and H are universal.

## 1. Is magnetic flux density the same as magnetic field strength?

No, magnetic flux density (B) and magnetic field strength (H) are two different physical quantities. Magnetic flux density measures the amount of magnetic flux passing through a given area, while magnetic field strength measures the intensity of the magnetic field at a specific point.

## 2. Can magnetic flux density be negative?

Yes, magnetic flux density can be negative. This typically occurs when the direction of the magnetic field is opposite to the direction of the area vector used to calculate the flux.

## 3. Is magnetic flux density a scalar or vector quantity?

Magnetic flux density is a vector quantity, as it has both magnitude and direction. Its direction is given by the direction of the magnetic field lines.

## 4. Does magnetic flux density depend on the material?

Yes, magnetic flux density can vary depending on the material through which the magnetic field passes. Materials with high permeability, such as iron, will have a higher magnetic flux density compared to materials with low permeability, such as air.

## 5. Is magnetic flux density conserved?

No, magnetic flux density is not conserved. It can change as the magnetic field or the area through which it passes changes. However, the total magnetic flux through a closed surface is always conserved.

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