Faraday?s experiments on electromagnetic induction were carried out during the 1830s. The phenomenon of electromagnetic induction takes place in a current that runs through a circuit (coil) as the magnetic flux in that circuit changes. The magnetic flux Φ through the area S is Φ = BScosα, where B is the magnitude of the magnetic field and α is an angle between the vector B and the vector of normal n to the plane of the circuit. In the case of a long coil, the net magnetic flux is the sum of individual magnetic fluxes through each loop in the coil. The magnetic flux through a coil can be changed due to two reasons: - changes in the magnetic field over time - motion of the coil in the magnetic field. In both cases, the process of electromagnetic induction runs in a similar fashion. Faraday's law expresses the induced emf in a circuit through the rate of change of the magnetic flux εind = - ΔΦ/Δt. The direction of the induced current can be determined using Lenz's law, which states that the direction of any magnetic induction effect opposes the cause that produces it. The source of the magnetic field producing the magnetic flux through the coil can be a magnet, or another coil with a current running through it. Induced current arises when relative motion of the coil and the source of the magnetic field take place. If another coil produces the magnetic field, induced current also emerges when the switch opens or closes the second coil.