What is the relationship between electricity and magnetism?

Electricity and magnetism are unified phenomena — electromagnetism. Key relationships: (1) ELECTRIC CURRENT creates a MAGNETIC FIELD around the wire (Oersted's discovery, 1820). Direction follows the right-hand rule: thumb in direction of current, fingers curl in direction of magnetic field. Field strength = μ₀I/(2πr) for a straight wire, where r is distance. Coiling the wire (solenoid) concentrates the field — basis for electromagnets. (2) CHANGING MAGNETIC FIELD creates an ELECTRIC FIELD that drives current in conductors (Faraday's discovery, 1831). Basis for generators, transformers, inductors, motors. (3) UNIFICATION (Maxwell's equations, 1860s): four equations describe all classical electromagnetism — Gauss's law (electric), Gauss's law for magnetism, Faraday's law of induction, Ampère's law with Maxwell's correction. They predicted electromagnetic waves traveling at the speed of light, ultimately unifying optics with electromagnetism. Light is an electromagnetic wave. Modern physics treats electricity and magnetism as different aspects of the same field — they appear differently depending on reference frame. Practical implications: (1) ELECTRIC MOTORS — current in a wire within a magnetic field experiences a force (F = IL × B); causes rotation in motor coils; converts electrical to mechanical energy; (2) GENERATORS — rotating coil in magnetic field induces voltage; converts mechanical to electrical; (3) TRANSFORMERS — AC in primary creates changing magnetic field; secondary coil sees changing field; voltage induced; (4) RADIO/COMMUNICATIONS — accelerating electrons (in antennas) create electromagnetic waves; (5) MRI — strong magnetic fields align nuclear spins; radio pulses then perturb them; signals back from the relaxing nuclei produce images; (6) MAGNETIC LEVITATION TRAINS (maglev) — magnetic forces support and propel trains; (7) PARTICLE ACCELERATORS — magnetic fields steer charged particles in beam; (8) HARD DRIVES — magnetic regions on disk encode data; read/write heads detect/change magnetization. Lorentz force: F = qE + qv × B (charged particle in electric and magnetic fields experiences force). Underlies operation of CRTs, particle accelerators, mass spectrometers, plasma physics. ASVAB EI may test basic understanding that current causes magnetic fields and that changing fields induce currents — both crucial to electrical engineering.