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Residual induction (Br), also known as residual flux density, is the magnetic flux remaining in a magnetic material after an applied magnetizing field (H) is reduced to zero following saturation in a closed circuit. Measured in Gauss (G) or Tesla (T), it defines the maximum baseline flux density a permanent magnet can retain without external demagnetizing influences.
Industrial Applications
In magnetic engineering, Br serves as the primary indicator of a material's inherent field strength, directly dictating how much magnetic flux a component can deliver across an operational air gap. Engineers measure residual induction using closed-circuit hysteresisgraphs (B-H permeameters) that drive a test sample to full saturation and record the flux density point where magnetizing force equals zero. In real-world applications, such as high-torque brushless DC motors, linear drives, and magnetic torque couplings, a higher Br enables smaller design footprints and greater mechanical force output without increasing overall motor volume.
Technical Specifications
Symbol & Units: Br; measured in Gauss (G) in CGS units or Tesla (T) / millitesla (mT) in SI units (1 Tesla = 10,000 Gauss).
Hysteresis Coordinate: Denotes the vertical intercept on the B-H hysteresis curve where magnetic field strength H = 0 Oe (or A/m).
Operating Flux Density (Bd): In open magnetic circuits, actual operating flux density (Bd) is always less than Br (Bd < Br) due to self-demagnetization geometry factors.
Manufacturing Considerations: Thermal sensitivity causes reversible losses in Br based on a material's temperature coefficient. Additionally, raw material batching and sintering variations typically yield Br manufacturing tolerances of +/- 3% to +/- 5%.
Related Case Studies and Products
To see how Br interacts with coercivity (Hc) during product selection, read our technical overview, The Curve That Tells You Everything: BH Curves for Non-Engineers. If you are developing high-field magnetic dipoles, sputtering magnetrons, or precision voice coils requiring specific residual flux targets, review our magnetic solutions and product development services.
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