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More precisely, the term magnetic moment normally refers to a system's magnetic dipole moment, which produces the first term in the multipole expansion [note 1] of a general magnetic field. Both the torque and force exerted on a magnet by an external magnetic field are proportional to that magnet's magnetic moment.
The magnetic field of a current loop. The ring represents the current loop, which goes into the page at the x and comes out at the dot. In classical physics, the magnetic field of a dipole is calculated as the limit of either a current loop or a pair of charges as the source shrinks to a point while keeping the magnetic moment m constant.
A magnetic field (sometimes called B-field [1]) is a physical field that describes the magnetic influence on moving electric charges, electric currents, [2]: ch1 [3] and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field.
10 −6 –10 −3 G – the magnetic field of Galactic molecular clouds. Typical magnetic field strengths within the interstellar medium of the Milky Way are ~5 μG. 0.25–0.60 G – the Earth's magnetic field at its surface; 4 G – near Jupiter's equator; 25 G – the Earth's magnetic field in its core [4] 50 G – a typical refrigerator magnet
kg −1 ⋅m −3 ⋅s 3 ⋅A 2: B magnetic flux density, magnetic induction: tesla: T = Wb/m 2 = N⋅A −1 ⋅m −1: kg⋅s −2 ⋅A −1: Φ, Φ M, Φ B magnetic flux: weber: Wb = V⋅s kg⋅m 2 ⋅s −2 ⋅A −1: H magnetic field strength ampere per metre: A/m A⋅m −1: F magnetomotive force: ampere: A = Wb/H A R magnetic reluctance ...
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
Blender (30 cm or 1 ft away) [5] 1.3 μT to 2.7 μT: 13 mG to 27 mG: High power (500 kV) transmission lines (30 m or 100 ft away) [6] 6 μT: 60 mG: Microwave oven (30 cm or 1 ft away) [5] 10 −5 T 10 μT: 100 mG: 24 μT: 240 mG: Magnetic tape near tape head: 31 μT: 310 mG: Earth's magnetic field at 0° latitude (on the equator) 58 μT: 580 mG
As such, they are often written as E(x, y, z, t) (electric field) and B(x, y, z, t) (magnetic field). If only the electric field (E) is non-zero, and is constant in time, the field is said to be an electrostatic field. Similarly, if only the magnetic field (B) is non-zero and is constant in time, the field is said to be a magnetostatic field.