When selecting the best magnet for your application, one of the most important things to consider is air gap. But, what is air gap? In this blog, we will provide a quick overview of air gap and how it affects a given magnet’s performance.
Explaining Air Gap:
The best way to explain the concept of air gap is by using an example. Imagine you have a magnetic iron bar. When you hold a magnet to the face of the iron bar, it will attract to the bar with its full magnetic strength. Not only did the magnet instantly attract, but the magnet is also now firmly attached to the iron bar and will require a great deal of force to move.
Now, imagine there is a plank of wood resting on top of the iron bar. When you hold the magnet to the plank of wood, depending on the strength of the magnet it will still attract to the iron bar beneath the wood. However, the magnet will not be held as firmly in place as it was when it was allowed to attract to the bar without the piece of wood in between serving as a barrier. In magnetic terminology, the wood is not defined as a barrier—rather, the plank of wood represents the air gap.
An air gap is not necessarily empty air. Rather, air gap can be any non-magnetic material placed in a magnetic circuit that increases the reluctance of the magnetic circuit. In simple terms, an air gap is a piece of non-magnetic material that creates space between a magnet and a magnetic material. An air gap can be made of materials such as wood, plastic, non-magnetic metals like aluminum, and more. If a magnet has a coating, such as a non-magnetic nickel or rubber epoxy coating, this coating is contributing to the air gap present. The greater the air gap, the more prevalent the loss of strength will be.
How Does Air Gap Affect Magnet Selection?
If there is a great deal of air gap in your application, it is important to select a magnet with greater strength in order to compensate for the magnetic strength lost as a result of increased air gap. For example, if you are mounting a magnetic hook to a wall in a home or office building, the magnetic field must travel through drywall, wood, insulation, and other non-magnetic materials in order to reach the wall stud it is attracting to. This application has a large air gap present. In comparison, a magnetic hook being mounted directly to an iron beam in a garage or warehouse does not have very much air gap present at all, aside from the actual air.
The magnetic hook being mounted to the wall in the home or office building may require a greater strength to successfully attract and hold to the wall stud beneath the wall’s surface due to the greater amount of air gap present. If air gap is not taken into account, the performance of the magnet may not be suitable for the application. To avoid this kind of problem, we recommend you consult with one of our experts at BuyMagnets.com about selecting the best magnet for your application.