Frequently Asked Questions about NdFeB Magnet:
- What is a magnetic field? What are magnetic field lines?
- How are magnetic fields measured?
- What are Neodymium magnets made of?
- If I have a Neo magnet with a Br of 12,300 Gauss, should I be able to measure 12,300 Gauss on its surface?
- Which are the strongest magnets?
- Why the grade of a magnet is important?
- What things will Neodymium magnets damage?
- How long will a magnet stay magnetized?
Q:What is a magnetic field? What are magnetic field lines?
Magnetic fields are historically described in terms of their effect on electric charges. A moving electric charge, such as an electron, will accelerate in the presence of a magnetic field, causing it to change velocity and its direction of travel. This is, for example, the principle used in televisions, computer monitors, and other devices with CRTs (cathode-ray tubes). In a CRT, electrons are emitted from a hot filament. A voltage difference pulls these electrons from the filament to the picture screen. Electromagnets surrounding the tube cause these electrons to change direction, so they hit different locations on the screen.
Q:How are magnetic fields measured?
The strength of a magnetic field is measured in units of Gauss (G), or alternatively, in Tesla (T). In the MKS (metric) system of units, 1 T = 1 kilogram*ampere/second 2 = 104 G.
Q:What are Neodymium magnets made of?
Not just Neodymium! Neodymium itself is actually a element number 60 on the periodic table. Neodymium magnets are actually made up of a compound called NIB, for Neodymium Iron Boron (Nd2Fe14B). This compound is one of the strongest known ferromagnetic materials.
Q:If I have a Neo magnet with a Br of 12,300 Gauss, should I be able to measure 12,300 Gauss on its surface?
No. The Br value is measured under closed circuit conditions. A closed circuit magnet is not of much use. In practice, you will measure a field that is less than 12,300 Gauss close to the surface of the magnet. The actual measurement will depend on whether the magnet has any steel attached to it, how far away from the surface you make the measurement, and the size of the magnet (assuming that the measurement is being made at room temperature). For example, a 1" diameter Grade 35 Neo magnet that is 1/4"long, will measure approximately 2,500 Gauss 1/16" away from the surface, and 2,200 Gauss 1/8" away from the surface.
Q:Which are the strongest magnets?
The most powerful magnets available today are the Rare Earths types. Of the Rare Earths, Neodymium-Iron-Boron types are the strongest. And it's Bhmax value could reach as high as 64MGOe theoretically, and in practice, 62MGOe has been achieved. In China,Bhmax value of NdFeB magnets has achieved 54Mgoe.Working temperature of normal NdFeB magnets is below 80 °C, EH grade could withstand 200°C. In Germany, the max. working temperature of NdFeB magnets has achieved 280~300°C in Lab.
Q:Why the grade of a magnet is important?
The grade of a magnet (N35, N38, N40, N45, etc) is important because it specifies the quality of material used to construct the magnet. All else being equal, the higher the quality of materials used to construct the magnet, the greater the magnets strength.
Q:What things will Neodymium magnets damage?
Neodymium magnets can damage magnetic based storage devises such as hard drives, floppy disks and credit cards. They can also affect computer monitors, VCR's and TV's. Large magnets can be hazardous to pacemakers.
Q:How long will a magnet stay magnetized?
Sintered Nd-Fe-B magnets will remain magnetized indefinitely. They will keep magnetic properties permanently if they are not affected by external environment. And they will only lose magnetic properties when environment temperature exceeds those they could withstand. Generally the magnet will experience a degradation in its physical properties, such as corrosion, prior to it demagnetizing because of age. However, heat and high magnetic fields can demagnetize these magnets.