Magnetization by Coil

The magnetic field around a straight wire is relatively weak. However, a stronger field can be created by coiling the wire around a piece of soft iron, forming an electromagnet, also known as a solenoid. The magnetic field around a current-carrying solenoid is similar to that of a bar magnet. A solenoid is essentially a coil made up of multiple turns of insulated copper wire, tightly wrapped in a cylindrical shape. One end of the solenoid behaves like a magnetic North Pole, while the other end behaves like the South Pole. Inside the solenoid, the magnetic field lines are parallel and straight, indicating that the field strength is uniform at all points inside the solenoid. When a soft iron rod is placed inside the solenoid, it becomes an electromagnet. Soft iron is preferred as the core material for solenoids because it produces the strongest magnetic field when the current flows, and unlike steel, it does not retain its magnetism when the current is switched off. If a steel bar is placed inside the solenoid, it becomes a permanent magnet, retaining its magnetism after the current is turned off. This characteristic makes steel unsuitable for electromagnets but useful in creating permanent magnets, which are essential in devices such as electric motors, generators, loudspeakers, and microphones.