The figure shows hysteresis curves for three different...

The figure shows hysteresis curves for three different materials. A hysteresis curve is a plot of the magnetic field strength inside the material $(B)$ as a function of the externally applied field $\left(B_{0}\right)$. (a) Which material would make the best permanent magnet? Explain. (b) Which would make the best core for an electromagnet? Explain.

Key Concepts

Magnetic Core Material for Electromagnets

For electromagnets, the core material is chosen for its ability to rapidly respond to changing magnetic fields. This generally means selecting materials with high magnetic permeability and low coercivity, so that the core can be easily magnetized and demagnetized with minimal energy losses. The design aims to maximize the induced magnetic field when current is applied without retaining significant magnetization when the current is turned off.

Remanence

Remanence, or residual magnetism, is the amount of magnetization that remains after the external magnetizing field is removed. A high remanence is essential for permanent magnets because it means that the magnet will maintain a strong magnetic field even without an applied external field. In contrast, for electromagnets, a low remanence is typically preferred to ensure that the magnetization can be effectively controlled and reversed when the current is altered.

Hysteresis Curve

A hysteresis curve is a graphical representation that plots a material’s magnetic response (its magnetic induction) as a function of the applied magnetic field. It encapsulates how a material becomes magnetized, retains magnetization, and demagnetizes when the external field is cycled. This curve is fundamental in understanding and comparing the magnetic properties of different materials over a complete cycle of magnetization and demagnetization.

Coercivity

Coercivity is a measure of a material’s resistance to changes in its magnetization; specifically, it denotes the magnitude of the reverse external field required to bring the magnetic induction to zero after the material has been saturated. High coercivity indicates that a material retains its magnetization well, which is crucial for permanent magnets, while low coercivity is generally desirable for materials used in electromagnet cores to allow for easier changes in magnetization without significant energy loss.

Transcript

Please give Ace some feedback