How do we know electromagnetic force exists?

The fact that magnetized material exists in nature at all is evidence of its existence.

Additionally, there are "true north" and "magnetic north," which are 1.5 degrees apart.

The axial point around which the earth rotates, either northward or southward, is referred to as true north.

The direction that a compass points in relation to the true north is known as magnetic north. The existence of an electromagnetic force—in this case, the earth's electromagnetic field—directly affects the small piece of metal in a compass; the reason for the 1.5 degree offset is unknown, but the earth does produce an electromagnetic field from its core.

The existence of electromagnetic force is confirmed through empirical observations, experiments, and mathematical models, supported by evidence such as electromagnetic interactions, Maxwell's equations, and the behavior of charged particles.

We know electromagnetic force exists through various experimental observations and theoretical developments in physics. Here are some key pieces of evidence and reasoning:

1. Coulomb's Law: Coulomb's law describes the electrostatic force between charged particles. The force between two charged particles is given by ( F = k \frac{q_1 q_2}{r^2} ), where ( k ) is Coulomb's constant, ( q_1 ) and ( q_2 ) are the charges of the particles, and ( r ) is the distance between them. Experimental verifications of Coulomb's law provide strong evidence for the existence of electric force.

2. Magnetic Forces: The interaction between magnetic poles and moving charges is described by magnetic forces. The force on a moving charged particle in a magnetic field is given by the Lorentz force equation ( F = q(v \times B) ), where ( q ) is the charge of the particle, ( v ) is its velocity, and ( B ) is the magnetic field. Experimental observations of magnetic interactions and behaviors, such as the deflection of charged particles in a magnetic field, confirm the existence of magnetic force.

3. Electromagnetic Induction: Faraday's law of electromagnetic induction describes how a changing magnetic field can induce an electromotive force (emf) and, subsequently, an electric current in a conductor. This phenomenon has been experimentally verified and is the principle behind electric generators and transformers, providing evidence for the interconnectedness of electric and magnetic forces.

4. Electromagnetic Waves: James Clerk Maxwell formulated a set of equations, known as Maxwell's equations, which describe how electric and magnetic fields interact and propagate. These equations predict the existence of electromagnetic waves, which include radio waves, microwaves, infrared, visible light, ultraviolet light, X-rays, and gamma rays. The experimental discovery and subsequent understanding of these electromagnetic waves confirm the existence and properties of electromagnetic force.

5. Quantum Electrodynamics (QED): QED is the relativistic quantum field theory of electrodynamics. It provides a theoretical framework for understanding the behavior of electrically charged particles and the interactions between light (photons) and matter (electrons and positrons) in terms of electromagnetic force. QED has been extremely successful in predicting and explaining various phenomena in the realm of atomic and subatomic particles, providing strong theoretical support for the existence of electromagnetic force.

In summary, the existence of electromagnetic force is supported by a combination of experimental observations, such as Coulomb's law, magnetic interactions, and electromagnetic induction, as well as theoretical developments, including Maxwell's equations and Quantum Electrodynamics.