If current flows through a wire wound into a coil (solenoid), what is created?

A coil of wire carrying current behaves like a bar magnet — this device is called an ELECTROMAGNET or SOLENOID. The magnetic field strength depends on: (1) CURRENT — more current = stronger field (proportional); (2) NUMBER OF TURNS — more turns concentrate the field; (3) CORE MATERIAL — iron core dramatically increases field strength (typically 1000x) due to high magnetic permeability; (4) COIL GEOMETRY — tighter, denser coils make stronger fields. Right-hand rule for solenoid: curl right-hand fingers in the direction of current flow; thumb points to the NORTH pole of the resulting magnet. Applications: (1) ELECTROMAGNETS — large lifting magnets in scrapyards; door locks; magnetic levitation; (2) RELAYS — small current activates electromagnet, which mechanically closes a switch controlling a larger circuit; (3) SOLENOIDS — coil with a movable iron core; energizing the coil pulls the core in; used in solenoid valves (control flow of fluids/gas), starter motors (engaging starter to flywheel), pinball machines, door locks; (4) MOTORS — coils in rotor and/or stator create magnetic fields; rotational force from interaction of fields; (5) GENERATORS — reverse of motors; (6) LOUDSPEAKERS — varying current in coil within magnetic field moves the coil and attached cone, producing sound; (7) MRI MACHINES — extremely powerful superconducting electromagnets create magnetic fields for imaging. Permanent magnets and electromagnets share the property of magnetic field but: permanent magnets have constant field strength (set by material); electromagnets have variable field controlled by current — turn off the current, field disappears. Magnetic poles: north and south, attract opposite poles, repel like poles. Earth has a magnetic field that compass needles align with — Earth's magnetic NORTH POLE is actually a SOUTH magnetic pole (which attracts compass north needles).