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Electric forces also allow different atoms to combine into molecules, including the macromolecules such as proteins that form the basis of life. Meanwhile, magnetic interactions between the spin and angular momentum magnetic moments of electrons also play a role in chemical reactivity; such relationships are studied in spin chemistry.
Lorentz force on a charged particle (of charge q) in motion (velocity v), used as the definition of the E field and B field. Here subscripts e and m are used to differ between electric and magnetic charges. The definitions for monopoles are of theoretical interest, although real magnetic dipoles can be described using pole strengths.
In the lab frame, the electron is moving and so feels a magnetic force from the current in the wire but because the wire is neutral it feels no electric force. But in the electron's rest frame , the positive charges seem closer together compared to the flowing electrons and so the wire seems positively charged.
This equation can be derived from the energy stored in a magnetic field. Energy is force times distance. Rearranging terms yields the equation above. The 1.6 T limit on the field [17] [19] previously mentioned sets a limit on the maximum force per unit core area, or magnetic pressure, an iron-core electromagnet can exert; roughly:
Similarly, if only the magnetic field (B) is non-zero and is constant in time, the field is said to be a magnetostatic field. However, if either the electric or magnetic field has a time-dependence, then both fields must be considered together as a coupled electromagnetic field using Maxwell's equations.
Faraday's law is a single equation describing two different phenomena: the motional emf generated by a magnetic force on a moving wire (see the Lorentz force), and the transformer emf generated by an electric force due to a changing magnetic field (described by the Maxwell–Faraday equation).
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: inverse henry: H −1 = A/Wb kg − ...
The electric field (E) is the dual of the magnetic field (H). The electric displacement field (D) is the dual of the magnetic flux density (B). Faraday's law of induction is the dual of Ampère's circuital law. Gauss's law for electric field is the dual of Gauss's law for magnetism. The electric potential is the dual of the magnetic potential.