Electromagnetism is one of the four fundamental forces of nature. It describes how electric charges create electric fields, how moving charges create magnetic fields, and how these fields interact with each other to produce electromagnetic phenomena.
Electric fields are invisible force fields created by electric charges. The strength of the field depends on the magnitude of the charge and decreases with the square of the distance. Field lines point away from positive charges and toward negative charges, showing the direction a positive test charge would move.
Magnetic fields are created by moving electric charges, such as electric currents flowing through wires. Unlike electric field lines, magnetic field lines form closed loops and have no beginning or end. The strength of the magnetic field around a wire depends on the current, and the direction follows the right-hand rule.
Electromagnetic waves are created when electric and magnetic fields oscillate together. The electric and magnetic fields are perpendicular to each other and to the direction of wave propagation. These waves travel at the speed of light and include radio waves, visible light, X-rays, and gamma rays.
To summarize what we have learned: Electromagnetism is a fundamental force that unifies electric and magnetic phenomena. Electric fields are created by charges while magnetic fields are created by moving charges or currents. When these fields change, they create electromagnetic waves that travel at the speed of light. This understanding forms the basis for countless modern technologies.