Both electromagnets and permanent magnets have been widely used in many applications. Permanent magnets such as bar magnets have been applied in hard drives, vehicles and magnetic hooks. Electromagnets such as coils are most frequently used in transformers and various medical devices. In some applications, both electromagnets and permanent magnets have been used together. What is the main difference between electromagnets and permanent magnets, and how do we select the right one for our application?
Permanent Magnets
Permanent magnets are made of strongly magnetic hard materials and they can keep their magnetic characteristics without external stimulus. Due to the strong magnetic properties in materials such as NdFeB, permanent magnets are a perfect selection to create consistent strong force to attract other objects at close distance. The force between two 8 cm NdFeB cube magnets can easily reach up to 5,000 newtons when the two magnets stick together. In many applications such as magnetic hooks the permanent magnets can provide long-time grabbing force without any additional energy input.
On the other hand, the disadvantages of permanent magnets are also caused by their material properties. Since these magnets keep their magnetic properties, they can never be turned off, nor can the force be controlled when their relative positions are fixed — which makes them hard to apply to applications that require changing forces. The force of permanent magnets becomes inefficient at long distances as the force decays with the cube of distance. One may notice the force between two 8 cm NdFeB magnets quickly drops from 5,000 to 100 newtons when their distance increases from 0 cm to 10 cm. Finally, a permanent magnet field can only be created below a certain temperature; as a result, they are not suitable for hot-device applications.
Electromagnets
Electromagnets are just like the opposite of permanent magnets. The magnetic field is created by current flowing through a solenoid. The magnetic properties of the coil depend on the current flowing through the wires. Due to this property, electromagnets are the most frequent type used in applications that require fast-changing magnetic fields or precisely controlled fields. One example is in MRI, where it is often needed to create an accurate field or field gradient at a specific location in space; by changing the current in different coils one can easily achieve precise control of the magnetic field in space, while it is almost impossible to get the same result by using permanent magnets. By playing with different current input, it is possible to create complex and real-time changing field arrangements with coils.
The main disadvantage of electromagnets is on the energy-transfer side. While permanent magnets are magnetized in advance and do not need energy input during application, electromagnets require a constant current source. This property makes electromagnets much less efficient at creating strong magnetic force at close distances compared to permanent magnets. Due to different variables related to current source disturbance and heating, electromagnets require more care on the design and maintenance side compared to permanent magnets in order to keep a high-precision field output.
Conclusion
At SM Magnetics, a leading authority in magnetic solutions, our expertise extends to both electromagnets and permanent magnets. We specialize in guiding clients through the selection process, ensuring optimal magnetic solutions tailored to their unique needs. Whether you’re exploring magnetic circuit design or seeking production-ready solutions, our technical team stands ready to assist.
For more insights into the capabilities of electromagnets and permanent magnets, contact our technical experts today.
About SM Magnetics
SM Magnetics is a privately owned company, providing assistance with magnets, magnetic circuit design, engineering support, and production. For more information contact our technical staff or visit our website.