Circular motion of an electron in a magnetic field

In summary: However, the strength of the interaction depends on the velocity of the electron. If the electron is not moving, the interaction will be weaker compared to when it is moving. In summary, when an electron is introduced into a magnetic field created by electric current passing through a vertical, infinite wire, it will experience a circular motion around the wire due to the Lorentz force. This force is not conservative and leads to a decrease in the electron's total mechanical energy over time. This change in energy is not related to the electron's spin, but rather to the emission of electromagnetic radiation. The spin does play a role in the electron's magnetic properties, but it only affects the force when the electron is moving. When the electron is not moving, there
  • #1
Cathr
67
3
Imagine we take a vertical, infinite wire and we let electric current pass through. The charges create magnetic field all around the wire.

Now if we introduce an electron in the magnetic field, it will have a circular motion around the wire. The Lorentz force is not conservative, this means that there will be a change in the total mechanical energy. After a period, when the particle arrives at the starting point, it will have less energy.

Is this change due to the change in the electron's spin? If so, why does it happen? (We are placing the electron in the vacuum and there is no friction)
 
Physics news on Phys.org
  • #2
Cathr said:
The Lorentz force is not conservative
You are probably thinking about synchrotron radiation or bremsstrahlung. Energy will be carried away in the form of EM radiation.

It has nothing to do with the electron's spin. Accelerating charged particles emit Larmor radiation.
 
  • Like
Likes Cathr
  • #3
Why do you think that the electron will move around the wire? The magnetic force on a moving charge is not along the magnetic field lines. Magnetic force on a static charge is zero. What the electron does depends on the initial speed (when you "introduce" it).
 
  • Like
Likes Cathr
  • #4

Thanks a lot!
 
  • #5
Thanks, this makes sense!
However, one thing that I don't understand is the particle's spin. If it is responsible for the electron's magnetic properties, why doesn't it "feel" the Lorentz force even when it's static?
 
  • #6
I don't understand your question. The Lorentz force just depends on the charge and the velocity of the particle in an electromagnetic field. The spin doesn't affect the charge of the electron or the linear motion.
 
  • #7
What I meant is, if spin is giving the particle its magnetic properties, why doesn't it feel the magnetic field even when it's not moving?
 
  • #8
Cathr said:
What I meant is, if spin is giving the particle its magnetic properties, why doesn't it feel the magnetic field even when it's not moving?
The spin is related to the electron's fundamental magnetic moment (with a gyro-factor around 2, with the deviations from that value being among the best understood quantities of theoretical physics in terms of QED), and as any magnetic moment, there's a force on the electron for inhomogeneous magnetic fields from it (and the spin precesses around the direction of the magnetic field).
 
  • #9
Cathr said:
why doesn't it feel the magnetic field even when it's not moving?
It does. The electron will interact with an external magnetic field.
 

What is circular motion of an electron in a magnetic field?

When an electron moves through a magnetic field, it experiences a force perpendicular to its velocity, causing it to follow a circular path. This is known as circular motion of an electron in a magnetic field.

What causes an electron to move in a circular path in a magnetic field?

The force that causes an electron to move in a circular path in a magnetic field is known as the Lorentz force. It is the result of the interaction between the magnetic field and the electric charge of the electron.

How does the strength of the magnetic field affect the circular motion of an electron?

The strength of the magnetic field directly affects the radius of the circular path that the electron follows. A stronger magnetic field will result in a smaller radius, while a weaker magnetic field will result in a larger radius.

What is the relationship between the speed of the electron and the strength of the magnetic field?

The speed of the electron is directly proportional to the strength of the magnetic field. This means that as the strength of the magnetic field increases, the speed of the electron also increases, resulting in a tighter circular path.

Is circular motion of an electron in a magnetic field a constant motion?

No, the circular motion of an electron in a magnetic field is not a constant motion. This is because the direction of the force and the resulting circular path are constantly changing as the electron moves through the magnetic field.

Similar threads

I The vector math of relative motion of wire-loop & bar magnet
    • Electromagnetism
Replies
1
Views
1K
I Magnetic field as result of length contraction
    • Electromagnetism
Replies
17
Views
1K
I Homopolar generator question: Magnetic “wake”
    • Electromagnetism
Replies
7
Views
1K
Magnetic field lines around electron and wire seem to contradict
    • Electromagnetism
Replies
6
Views
870
Current and stationary charges
    • Electromagnetism
Replies
8
Views
1K
Why is magnetic field B along a straight wire circular not radial?
    • Introductory Physics Homework Help
Replies
14
Views
1K
I Current through U-wire (rail gun): Violation of (naive) conservation of momentum?
    • Electromagnetism
2
Replies
61
Views
2K
How Fast Does an Electrical Impulse Travel in a Copper Wire?
    • Electromagnetism
3
Replies
100
Views
6K
Magnetic fields and moving electrons
    • Electromagnetism
Replies
1
Views
916
I Seeking the Equation of Motion for a charged mass attached to a spring
    • Electromagnetism
Replies
22
Views
2K

Hot Threads

Recent Insights

Back
Top