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Help and Advice with Magnets and Magnetic Products
We have over 25 years' experience working with magnets and magnetically receptive materials, if you have any questions which aren't covered here, please get in touch.
What’s the difference between an electromagnet and a permanent magnet?
Most magnets that you’ve handled will be permanent magnets (fridge magnets etc.) Permanent magnets produce their own magnetic field, which is consistent in size and strength.
The most common household magnets are ferrite magnets, which are those you’re likely to find on solid and flexible fridge magnets. The strongest permanent magnets are rare earth magnets. Both neodymium and samarium cobalt are examples of rare earth magnets.
An electromagnet however only produces a magnetic field when an electric current is run through it. The size and strength of the magnetic field can be increased and decreased by changing the electric current.
Electromagnets are commonly created by wrapping copper wire around an iron object. This coil forms a solenoid and when an electric current flows through it, it generates a magnetic core. The iron object becomes magnetic, but once the electric current is removed, reverts to its non-magnetic state.
What are rare earth magnets?
Rare earth magnets of well-known thanks to their strength. The most common are neodymium and samarium cobalt.
Neodymium magnets are made from a metallic alloy of neodymium, iron and boron (NdFeb). Samarium cobalt (SmCo) are made from samarium, cobalt and smaller amounts of copper, iron and other materials.
Despite the name, they are actually quite common materials and abundant. The term rare is applied as their distribution in the earth’s crust is quite wide and difficult to access.
What’s the difference between N35 and N38 Neodymium Magnets?
The grade of a neodymium magnet refers to the magnet’s strength and maximum energy output. An N35 magnet would have a maximum energy product of 35 Mega-Gauss Oersted (MGOe), whereas an N38 magnet has an energy product of 35 MGOe. In general terms, the higher the number, the stronger the magnet.
What are magnetic poles?
A magnetic pole is the area on a magnetic which has the strongest magnetic field in a specific direction i.e. North or South.
The magnet’s poles are the area where the lines of a magnetic field leave the magnet and eventually return. No matter how small a magnet is, or even if a magnet is broken, the magnet will still have magnetic poles.
Which pole should I use?
Both poles are equal in strength and will hold the same weight or stick to the same magnetically receptive material.
However, two similar poles will always repel each other - north will repel north and south repels south. If the magnets appear to push away from each other, simply flip one of the magnets over - opposite poles (north to south / south-to north) will always attract each other.
How can I identify magnetic poles?
The easiest way to detect a magnetic pole, is using a compass. Because compasses always point to THE North Pole in the Arctic, when you place the compass next to a magnet, the compass needle will always point toward the magnets South pole (remember, opposites attract).
There are also a range of smartphone apps which can identify which the polarity of a magnet face by pointing it at your phone.
How can I see a magnetic field?
The most common method, which you may remember from school, is to place a magnet under a sheet of paper and the sprinkle iron filings on top of the paper around the magnet. The iron filings will move around and rearrange themselves to accurately portray the shape of the magnet’s field. Alternatively, you can buy magnetic field viewing film, which although a little more expensive, isn’t as messy as using iron filings.
What type of adhesive should I use with magnets?
Two-part epoxy adhesive is the most versatile adhesive, working with a wide range of magnets. However, epoxy can have difficulties bonding magnets to polythene-type plastics.
Can I make my magnet stronger?
Once a magnet has been magnetised, it can’t be made any stronger. Imagine that the magnet is a glass of water, once the glass is full, you can’t add any more water.
You could, however, add an extra glass.
Stacking 2 magnets together would essentially be the same as having a single magnet that is the combined size of the 2 magnets. If you stacked a pair of 10mm x 2mm magnets with a pull force of 1kg, you’ve essentially got a 10mm x 4mm magnet, which doubles the strength of the magnet.
However, once the length of the stack exceeds the diameter of the magnet, adding further magnets will only give small strength improvements.
So you could stack 5 10mm x 2mm magnets to reach optimum performance (a pull force of 5kg), but any additional magnets added would only produce a slight strength improvement.
Which part of the magnet is strongest?
The strongest part of the magnet is always on the magnets poles, but bear in mind that there is no strength difference between north or south poles.
What is pull and holding force?
Pull force refers to how much force (usually in kg) it takes to remove a magnet from a magnetically receptive surface. Holding force highlights how much weight a magnet will hold – this is usually seen with hook magnets.
How long do permanent magnets last?
If maintained correctly, a permanent magnet will keep its magnetism for many years. Neodymium magnets are estimated to lose only around 5% of their magnetism over 100 years. However, if a magnet is exposed to higher temperatures that is optimal or is kept in an environment where corrosion could occur, then a magnet will weaken.
Samarium cobalt magnets have higher maximum temperature (up to 350 degrees Celsius than neodymium magnets (around 80 degrees Celsius), but aren’t quite as strong. Unlike neodymium magnets, samarium cobalt magnets are resistant to corrosion.