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Overview
Electricity and magnetism is the branch of physics that studies electric charge, electric fields, current, voltage, resistance, magnetic fields, electromagnetic induction, and the interaction between electric and magnetic phenomena. It explains circuits, motors, generators, power grids, sensors, speakers, antennas, computers, medical devices, and electromagnetic radiation.
Although electricity and magnetism are often introduced separately, they are deeply connected. Moving charges create magnetic effects, changing magnetic fields can produce electric currents, and light itself is an electromagnetic wave.
Electricity
Electricity begins with charge. Electric charge is a property of matter that produces electric forces and electric fields. Like charges repel, opposite charges attract, and charge is conserved. In circuits, charges move through conducting paths as electric current. Voltage represents electric potential difference, while resistance describes how strongly a material or device opposes current.
Basic circuit analysis requires careful attention to source, path, load, and control. A battery or power supply provides potential difference. Conductors provide paths. Components such as lamps, resistors, motors, and sensors use electrical energy. Switches and control systems regulate flow.
Magnetism
Magnetism involves magnetic fields and magnetic forces. Permanent magnets produce magnetic fields because of microscopic magnetic structure. Electric currents also produce magnetic fields. Magnetic forces act on moving charges and current-carrying wires, which is why motors can convert electrical energy into mechanical motion.
Magnetism is not limited to bar magnets. It is central to compasses, motors, generators, transformers, speakers, MRI machines, data storage, electric vehicles, and power transmission systems.
Electromagnetic Induction
Electromagnetic induction occurs when a changing magnetic environment produces an electric effect. This principle makes generators and transformers possible. A generator converts mechanical motion into electrical energy by changing magnetic flux through coils. A transformer changes voltage levels in alternating-current systems by using changing magnetic fields between coils.
Induction shows why electricity and magnetism must be studied together. It also explains much of modern electrical infrastructure, from power plants to household chargers.