What is electromagnetism?

Electromagnetism studies electric charges and their relationships with electric and magnetic fields. Static electricity, magnets, electric currents and light are different expressions of the same fundamental interaction. Electronics, power generation and communication technologies rely on these relationships.

Electric and magnetic fields

1. Charge and electric fields Positive and negative charges interact electrically. Like charges repel and opposite charges attract. An electric field describes the effect a charge would experience at a location. Field lines are diagrams of direction and relative structure, not physical threads. 2. Current and potential difference Current is charge flow per unit time. Potential difference relates to an energy difference per unit charge. Circuit energy transfer cannot be explained simply as electrons racing through a wire: signals and fields matter too. 3. Magnetic interactions Moving charges and currents can create magnetic fields. A magnetic field can exert a force on a moving charge that also depends on its motion direction. A magnet’s behavior reflects collective microscopic magnetic properties. Not every metal is strongly attracted to a magnet.

Induction, waves and technology

4. Electromagnetic induction Changing magnetic flux through a circuit can generate an electromotive force. Generators use this principle to convert mechanical motion into electrical energy. Transformers also transfer energy through changing fields; ideal models omit real losses. 5. Maxwell and electromagnetic waves Maxwell’s equations unite electric and magnetic phenomena and show that changing fields can propagate as waves. Radio, microwaves, visible light and X-rays occupy different frequency ranges. They propagate at the same fundamental speed in vacuum. 6. Applications and distinctions Motors, antennas and many sensors rely on electromagnetism. Radiation’s effects depend on frequency, intensity, exposure duration and surroundings. Treating every kind of radiation as identical, or assuming invisibility implies identical properties, is scientifically incorrect.