Why lorentz force

Click on the Knife Switch to start the flow of current. The wire will swing in a direction perpendicular both to the magnet's field and to the movement of the charged particles.

Changing the direction of current flow by clicking the Flip Battery button, or the direction of the magnetic field by clicking the Flip Magnet button, will reverse the direction of the Lorentz force. The Reset button can be used to return the magnet and battery to their original positions. You can predict which way the wire will move by using the left-hand rule.

The equation of motion of a free particle of charge and mass moving in electric and magnetic fields is Figure Thompson's experiment. Let us analyze Thompson's experiment. Suppose that the rays are originally traveling in the -direction, and are subject to a uniform electric field in the -direction, and a uniform magnetic field in the -direction--see Fig.

Let us assume, as Thompson did, that cathode rays are a stream of particles of mass and charge. One can think of currents as a relative drift between oppositely charged particles.

Currents are defined by the motion of positive charges, so electrons move in the opposite direction. The purpose of this somewhat elaborate answer is to illustrate that the response of an electron is to effectively counteract the field acting on it. It is similar to the concept of induction in Faraday's law, whereby a current is induced to try and prevent magnetic flux from changing. Hmm, this last part is more confusing than I first thought. I wonder if the "or" should be an "and"?

Regardless, the particle responds to the field producing an effective current in the opposite sense to the one that produced the field. I don't like intuitive explanations that are not intuitive! Intuitive explanations cannot contains formulas and math. It should make an analogy, which, although not totally accurate, helps the reader to feel something behind a dry formula or theorem.

I search for some intuitive explanation for a Lorentz Force for a long time and now I've found one that I like very much. Let's start with a figure below , that shows the Lorentz force visualized as an interaction between imaginary magnetic tubes. Imagine one that is looking at a vertical magnet, south part to the left side and north part to the right side.

Now imagine a positive charge moving vertically through the magnetic lines. It generates a magnetic field around itself by the right hand rule. The lines of this field are horizontal and counterclockwise. Remember that parallel magnetic lines of force traveling in the same direction are normally consequence of a repulsion force. Parallel magnetic lines of force traveling in opposite directions are usually consequence of an attraction force.

If you are looking at the magnets and the moving charge in the vertical, in the back far side the magnetic lines external and charge generated are at the same direction, that is typically produced by a forward force. In the front near side the magnetic lines are at opposite direction, that is normally generated by a additional forward force. As a consequence, the particle experiences a force from the far side to the near side, with the dark arrow shown in the figure.

Finally, if the force had a component at the same direction to the speed, the force will generates a continuous speed increase. It will create kinetic energy increase forever, because the magnets don't need to be loaded. If the force had a component in the opposite direction to the speed, the charges will stop and there's no possible electric current inside a magnetic field.

However, it's a useful approach to explain concepts! How about this? The force acts on the charge causing it to accelerate The charged partial would never stay in place.

You are trying to solve without the whole equation, but your answer should look like this for a working model. Instead if the positive monopole disk you would replace it with your positive charged particle. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Is there an intuitive explanation for why Lorentz force is perpendicular to a particle's velocity and the magnetic field?

Ask Question. Asked 9 years, 5 months ago. Active 2 years, 6 months ago. Viewed 17k times. Improve this question. Stephen Jennings. Stephen Jennings Stephen Jennings 1 1 gold badge 5 5 silver badges 5 5 bronze badges. Add a comment. Active Oldest Votes. Improve this answer. More physical restatement of the argument The above is sort-of formal sounding, but it is just saying this: the magnetic field doesn't change sign under reversing the coordinates of space.

Hamiltonian argument and gauge invariance The best argument is from the concept of momentum potential or vector potential. Ron Maimon Ron Maimon 1. Intuitive doesn't mean not precise. The force is perpendicular to "v" and to "B", and one must argue this without relativity since it predates relativity, and inspires it. It only becomes non-arbitrary when you have relativity. Perhaps the right thing is to say "relativity" right at the start, but it won't justify why 19th century folks were sure they understood it before Einstein.

If you think this is a bad answer, perhaps I'll agree the reflection issue is no longer considered fundamental, and the Hamilton formulation might be arbitrary too but I don't think so. No one should expect technical writing to be easy, and no one should demand to understand everything at first reading - one wouldn't learn anything if one weren't challenged.

Not all answers work for everybody - so what. Indeed your answers sometimes lose me - so what - I'm damn glad people like you put the effort you do into your posts. Show 4 more comments. For the Lorentz transformation of the electromagnetic field, see en.

Unfortunately this is a bit beyond my knowledge, but I will be trying my best to understand it. Thank you. The first three paragraphs just restate that fact without explaining why it's true. The fourth, fifth, and sixth paragraphs are again just a statement of the fact, but now in fancier mathematical dress.

Art Brown Art Brown 5, 1 1 gold badge 24 24 silver badges 38 38 bronze badges. Though I start with a charged particle at rest net to a current carrying wire - no force.