Alexander Fufaev

Formula: Specific Charge of a Charged Particle in a Magnetic Field

Kreisbewegung einer Ladung im Magnetfeld

Electric charge

Electric charge of the particle (e.g. the electron) moving on a circular path in a magnetic field.

The ratio of the charge \(q\) to the mass \(m\) of the particle is called specific charge \( \frac{q}{m} \). For example, the electron has a specific charge \( \frac{q}{m} = - 1.758 \cdot 10^{11} \, \frac{\text C}{\text{kg} } \).


Mass of the charged particle.
  • If the particle is a electron, then the mass is \( m = 9.1 \cdot 10^{-31} \, \text{kg} \).
  • If the particle is a proton, then the mass is \( m = 1.67 \cdot 10^{-27} \, \text{kg} \).

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Velocity of the particle. It is greater the stronger the magnetic field \(\class{violet}{B}\) and the smaller the mass \(m\) of the particle.

Magnetic flux density (B-field)

Magnetic flux density, which describes how strong the magnetic field is as the charged particle moves.


Radius of the circular path on which the charged particle moves. By changing the magnetic field \(\class{violet}{B}\) you can easily make the radius \(r\) of the circular path larger or smaller.