Electromagnetic induction
Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field.
A current clamp
Image: Hawkins Electrical Guide Figure 292 Eddy currents in a solid armature
Image: Hawkins Electrical Guide Figure 293 Armature core with a few laminations showing effect on eddy currents
Image: Small DC Motor pole laminations and overview
In electromagnetism and electronics, electromotive force is an energy transfer to an electric circuit per unit of electric charge, measured in volts. Devices called electrical transducers provide an emf by converting other forms of energy into electrical energy. Other electrical equipment also produce an emf, such as batteries, which convert chemical energy, and generators, which convert mechanical energy. This energy conversion is achieved by physical forces applying physical work on electric charges. However, electromotive force itself is not a physical force, and ISO/IEC standards have deprecated the term in favor of source voltage or source tension instead.
A typical reaction path requires the initial reactants to cross an energy barrier, enter an intermediate state and finally emerge in a lower energy configuration. If charge separation is involved, this energy difference can result in an emf. See Bergmann et al. and Transition state.
Solar cell output voltage for two light-induced currents IL expressed as a ratio to the reverse saturation current I0 and using a fixed ideality factor m of 2. Their emf is the voltage at their y-axis intercept.