I've been learning about electromagnetism and recently saw the Lorentz Equation. I have questions that keeps bothering me and I could not figure it out by myself.

  1. So when we put two different poles of a magnet at a distance and then roll an iron ball in the middle of them; the ball accelerates due to the Force being perpendicular to both electric and magnetic field and all. The part that I do not understand is there is an increase in kinetic energy of the object but the magnetic field does no work since when we take the work integral , due to cross-product and v being parallel to ds, the dot product becomes 0. Then it is the electric field that does work on the iron ball. But then why does increasing the Tesla of the magnet increase $\Delta E$ of the object, since Tesla is the unit of the magnetic field, not the electric field shouldn't it change nothing?
  2. I know that Lorentz Force can be calculated with particles with known charges. How can the Lorentz force be calculated for solid objects such as metal balls?
  3. Can I calculate how much Tesla a magnet is from the Lorentz Force or from how much $\Delta E$ the object gained during a limited time period or distance?
  • $\begingroup$ The Lorentz force applies to charged particles. It cannot be straightforwardly applied to bulk, uncharged objects like steel balls. $\endgroup$
    – ProfRob
    Commented May 16, 2021 at 8:14
  • $\begingroup$ @ProfRob There is this short website I found spiff.rit.edu/classes/phys313/lectures/sol/sol_f01_long.html and it contains an equation at the bottom for the force. Would that work for my case? $\endgroup$
    – Mefecig
    Commented May 16, 2021 at 23:38

1 Answer 1


electrons in a beltway are essentially an electromagnet as long as the electrons are orbiting the nuclei the atom is polarized... for instance all P orbitals have two poles. the iron ball between two dissimilar poles, is conducting the magnetic flux through it's mass as well as the electrical current. All electrical current/moving electrons, produce/emit, a magnetic field. This magnetic field is then reacting to the increased field of the magnets when you increase the Tesla.


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