What is a disadvantage of temporary magnets?

Temporary magnets are characterized by their ability to exhibit magnetic properties only when they are within a certain magnetic field. Once that external magnetic influence is removed, they tend to lose their magnetism relatively quickly. This property makes them less reliable for applications where a constant magnetic field is required, as the absence of that field can lead to an immediate loss of magnetic capability.

In contrast, permanent magnets retain their magnetism without the need for continuous external energy, which is a significant advantage in many applications. The potential for temporary magnets to quickly lose their magnetism limits their usage in situations where enduring magnetic strength is paramount, such as in electric motors, generators, or magnetic storage.

The other options imply different limitations: reliance on a power supply, single-use only, or higher cost compared to permanent magnets, which do not accurately represent the inherent characteristics of temporary magnets. The core disadvantage lies primarily in their fleeting magnetism when the external magnetic source is removed.