Lorentz force is a law of physics, particularly electromagnetism, that describes the force interaction between magnetic fields of two charged particles. It was named after Hendrik Lorentz, a Dutch physicist during the 1800s who had great interest in the science of electromagnetism.
Lorentz force is best described by the equation
F=q(E + v x B)
where B is the strength of the magnetic field, E is the electric field, q is the charge on the particle and v is the velocity of the particle. It is expressed in “Newtons” as the unit of measure.
According to this equation, if a particle of charge q moves (through another magnetic field) with velocity v in the presence of an electric field E and a magnetic field B, then it will experience a reactive force. This reactive force is what is known as the Lorentz force.
The Lorentz force equation was actually derived from the famous Maxwell’s equation. There are variations of this basic equation of the Lorentz force. Other equations, which could be found on other textbooks, describe the magnetic force on a current-carrying wire, electromotive force in a wire loop moving through a magnetic field, and the force on a charged particle which might be traveling near the speed of light.
Another interesting fact revealed by the Lorentz force equation is the direction of the magnetic field, electron movement and of the Lorentz force itself. It is popularly known as the “Hand Rules” which can be easily understood in these photos.
When the charge on the moving particle is negative, the left hand rule is used.
Left Hand Rule
When the charge on the moving particle is positive, the right hand rule is used.
Right Hand Rule
Images Source: CK-12 Website
In our previous two experiments about “How to make an electromagnet?” and “How Magnetic Suction Works on Doorbells”, we realized how electromagnetism is produced. When electric current is induced to a wire, atoms start to become moving charges (either positive or negative depending on the flow of current) that act like small magnets pointing in different directions. The reactive force (or the Lorentz force) is the result of the magnetizing effect when the moving charge is brought near another magnetic field. The Hand Rules (left or right) provided clarification on the true direction of the magnetic field when a moving charge is either positive or negative.
For more scientific information about Lorentz force, check out this video demonstrating the Hand Rules in a very creative setup.
magnetic effect of electric current
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