What is Magnetic Hysteresis?

Magnetic hysteresis refers to the behaviour of ferromagnetic materials that exhibit residual magnetism, even after the applied magnetic field is removed. When a magnetic field is applied to a ferromagnetic material, such as iron, the material becomes magnetized, and the magnetic domains within it align themselves in the direction of the field. When the magnetic field is removed, the material retains some of its magnetization, and a residual magnetic field remains in the material. This phenomenon is known as hysteresis.

Understanding Magnetic Hysteresis Curves

Magnetic hysteresis can be illustrated using a graph of magnetic flux density (B) against magnetic field strength (H), called the magnetic hysteresis curve. The curve consists of two loops, one for increasing field strength and one for decreasing field strength. The area enclosed by the hysteresis curve represents the energy lost as heat during the magnetic cycle. The hysteresis curve is used to determine the magnetic properties of a material, including its coercivity, remanence, and saturation magnetization.

Applications of Magnetic Hysteresis

Magnetic hysteresis has many practical applications, including in magnetic storage media, such as hard drives and magnetic tapes, where it is used to store and retrieve data. It is also used in electromagnetic devices, such as motors and generators, where it helps to convert electrical energy into mechanical energy and vice versa. Magnetic hysteresis is also used in electronic sensors, such as magnetic field sensors, to detect changes in magnetic fields.

Example of Magnetic Hysteresis in Real Life

An example of magnetic hysteresis in real life is the use of magnets in credit and debit cards. These cards contain a magnetic stripe, which is coated with tiny magnetic particles that can be magnetized in one direction or the other. When the card is swiped through a card reader, the reader sends a magnetic field through the magnetic stripe, causing the particles to align in a certain pattern. This pattern is then read by the reader, allowing it to detect the information contained on the card. The residual magnetization in the stripe ensures that the information remains on the card even after it has been removed from the reader.