Permanent Magnet

Definition

A permanent magnet is a material that consistently produces a magnetic field without the need for an external power source. These magnets are typically made from materials like iron, nickel, cobalt, or alloys such as neodymium and samarium-cobalt. Unlike temporary magnets, which only exhibit magnetic properties when exposed to a magnetic field, permanent magnets maintain their magnetism over time.

5 Must Know Facts For Your Next Test

1. Permanent magnets can retain their magnetism for many years, but factors like temperature and physical damage can affect their strength.
2. The strength of a permanent magnet is measured in terms of its magnetic flux density, often given in teslas (T) or gauss (G).
3. Permanent magnets are widely used in various applications, including motors, generators, speakers, and magnetic storage devices.
4. The alignment of the magnetic domains in a permanent magnet is what allows it to maintain a stable magnetic field even when not influenced by external forces.
5. Different materials have varying coercivity levels, which determine how well they can retain their magnetism after being subjected to external magnetic fields.

Review Questions

• How do permanent magnets differ from temporary magnets in terms of their properties and uses?
  • Permanent magnets differ from temporary magnets primarily in their ability to retain magnetism over time. Permanent magnets maintain their magnetic properties without requiring an external power source, while temporary magnets only exhibit magnetism when subjected to an external magnetic field. This distinction makes permanent magnets suitable for applications like electric motors and hard drives, where a constant magnetic field is necessary.
• Discuss the role of temperature on the performance of permanent magnets and how it can affect their applications.
  • Temperature plays a crucial role in the performance of permanent magnets. As temperature increases, the thermal agitation can disrupt the alignment of the magnetic domains within the magnet, leading to a decrease in its overall strength. For instance, materials with low coercivity may lose their magnetization at elevated temperatures, limiting their use in high-heat environments. This sensitivity to temperature must be considered in applications such as motors or sensors that may experience fluctuating thermal conditions.
• Evaluate the significance of coercivity in the selection of materials for permanent magnets in various technological applications.
  • Coercivity is a critical factor in selecting materials for permanent magnets because it defines how well a material can resist demagnetization after exposure to an external magnetic field. High-coercivity materials are essential in applications requiring stable performance under varying conditions, such as in electric vehicles or aerospace technology. Evaluating coercivity allows engineers to choose appropriate materials that ensure reliability and efficiency across different operational environments, ultimately impacting device performance and longevity.

Related terms

Magnetization: The process by which a material becomes magnetized by aligning its internal magnetic domains.

Electromagnet: A type of magnet that generates a magnetic field through the flow of electric current, which can be turned on or off.

Magnetic Field Lines: Imaginary lines that represent the strength and direction of a magnetic field; they emerge from the north pole and enter the south pole of a magnet.