Faraday's law of induction
Faraday's law of induction is a law of physics proposed by English physicist Michael Faraday in 1831.[1] It is one of the basic laws of electromagnetism. The law explains the operation principles of generators, transformers and electrical motors.
Faraday's law of induction says that when a magnetic field changes, it causes a voltage.[2] That phenomenon was also found by Joseph Henry in 1831.[3] To describe the law, the magnetic flux and also a surface with a wire loop as border. This leads to the following surface integral:
- [math]\displaystyle{ \Phi_B = \iint\limits_{\Sigma(t)} \mathbf{B}(\mathbf{r}, t) \cdot d \mathbf{A} }[/math]
- ΦB is the magnetic flux
- dA is a small part of the moving surface
- B is the magnetic field
When the flux changes, it produces electromotive force. The flux changes when B changes or when the wire loop is moved or deformed, or when both happens. The electromotive force can then be calculated with the following equation:
- [math]\displaystyle{ \mathcal{E} = -N {{d\Phi_B} \over dt} }[/math]
- [math]\displaystyle{ \mathcal{E} }[/math] is the electromotive force
- N is the number of loops the wire makes
- ΦB is the magnetic flux of one loop
References
de:Elektromagnetische Induktion#Induktionsgesetz in Integralform