# E & B Fields from Moving Charges: The Magnetic Monopole Mystery

• cragar
In summary, the conversation discusses the relationship between E fields and B fields in different frames of reference. The speaker explains that while a stationary rod will primarily have an E field, a moving rod will also have a small B field. They also mention the concept of magnetic monopoles and why they are sought after, as well as the invariance of both E(dot)B and E2/c2 - B2.
cragar
Lets say I have a negative line charge on a long thin rod, if I am at rest with respect to that rod I will see an E field. But If I am moving with respect to that rod I will see a B field. So why are people looking for magnetic monopoles, If B fields are E fields in disguise, wouldn't the electrons need to show magnetic monopoles if they existed?

hi cragar!
cragar said:
Lets say I have a negative line charge on a long thin rod, if I am at rest with respect to that rod I will see an E field. But If I am moving with respect to that rod I will see a B field.

yes, but it's only a tiny-weeny B field …

it's still mostly an E field

E2/c2 - B2 is invariant (the same in all frames), so since it's positive for the stationary rod, it's always positive

(if the speed is tanhu, then |E| = cE0coshu and |B| = E0sinhu)

similary, a stationary magnetic monople (if it exists) will have E = 0, and so E2/c2 - B2 will be negative, in that and any other frame …

there's no frame transformation that will turn pure E into pure B

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I though it was E(dot)B that was invariant . Or is your way also equivalent. We can have frames where there is pure B then some E and B, but that probably doesn't help my case.

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The search for magnetic monopoles is driven by theoretical predictions and experimental evidence that suggest the existence of these particles. While it is true that a moving charge can create both an electric and a magnetic field, the properties and behavior of these fields are fundamentally different. The electric field is a vector quantity, meaning it has both magnitude and direction, while the magnetic field is a pseudovector, meaning it has magnitude but no direction. Additionally, the electric field is caused by the presence of electric charges, while the magnetic field is caused by the motion of electric charges.

The concept of a magnetic monopole, a particle with a single magnetic charge, is consistent with many theories in physics, such as the Grand Unified Theory and string theory. The existence of magnetic monopoles would also help to explain certain phenomena, such as the quantization of electric charge and the origin of the magnetic field in the universe.

While it is true that electrons do not exhibit magnetic monopole behavior, it is possible that other particles, such as magnetic monopoles, exist in the universe. The search for these particles is important in furthering our understanding of the fundamental laws of physics and could have significant implications for technology and energy production. Therefore, it is important to continue searching for magnetic monopoles and other particles that may help us better understand the universe.

## What are E & B fields from moving charges?

E & B fields from moving charges refer to the electric and magnetic fields that are created by the movement of charged particles. These fields are a fundamental aspect of electromagnetism and play a crucial role in many physical phenomena.

## How are E & B fields related to each other?

E & B fields are intimately related to each other, as they are both components of the electromagnetic field. The electric field is created by stationary or moving charges, while the magnetic field is created by moving charges. Together, they form a complex and interconnected system that affects the behavior of charged particles.

## Why is the existence of magnetic monopoles a mystery?

Magnetic monopoles, or particles with a single magnetic pole, are predicted by many theories in physics but have never been observed in nature. This is a mystery because all known magnets have both a north and south pole, and the existence of magnetic monopoles would fundamentally change our understanding of electromagnetism.

## Can magnetic monopoles be created artificially?

Although magnetic monopoles have not been observed in nature, they can be created artificially in certain materials. These artificial monopoles are not true monopoles, but rather quasiparticles that behave similarly to monopoles. However, creating true magnetic monopoles remains a challenge for scientists.

## What are the potential applications of magnetic monopoles?

The existence of magnetic monopoles could have significant implications for technology and science. They could potentially be used in more efficient and powerful magnetic devices, and their discovery would greatly advance our understanding of the universe and its fundamental laws.

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