Search results
Results From The WOW.Com Content Network
The magnetic field (marked B, indicated by red field lines) around wire carrying an electric current (marked I) Compass and wire apparatus showing Ørsted's experiment (video [1]) In electromagnetism , Ørsted's law , also spelled Oersted's law , is the physical law stating that an electric current induces a magnetic field .
Lenz's law predicts the direction of many effects in electromagnetism, such as the direction of voltage induced in an inductor or wire loop by a changing current, or the drag force of eddy currents exerted on moving objects in the magnetic field.
Magnetic current density, which has the unit V/m 2 (volt per square meter), is usually represented by the symbols and . [a] The superscripts indicate total and impressed magnetic current density. [1] The impressed currents are the energy sources. In many useful cases, a distribution of electric charge can be mathematically replaced by an ...
The magnetic field generated by a steady current I (a constant flow of electric charges, in which charge neither accumulates nor is depleted at any point) [note 8] is described by the Biot–Savart law: [21]: 224 = ^, where the integral sums over the wire length where vector dℓ is the vector line element with direction in the same sense as ...
The electric motor exploits an important effect of electromagnetism: a current through a magnetic field experiences a force at right angles to both the field and current. This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821.
The magnetic moment also expresses the magnetic force effect of a magnet. The magnetic field of a magnetic dipole is proportional to its magnetic dipole moment. The dipole component of an object's magnetic field is symmetric about the direction of its magnetic dipole moment, and decreases as the inverse cube of the distance from the object.
Therefore, the magnetic force term of the Lorentz force has no effect, and the force on the charge is given by ′ = ′ =. This demonstrates that the force is the same in both frames (as would be expected), and therefore any observable consequences of this force, such as the induced current, would also be the same in both frames.
The validity of Ampère's model means that it is allowable to think of the magnetic material as if it consists of current-loops, and the total effect is the sum of the effect of each current-loop, and so the magnetic effect of a real magnet can be computed as the sum of magnetic effects of tiny pieces of magnetic material that are at a distance ...