Faraday's law states that a changing magnetic field within a closed loop induces an electromotive force (EMF) in that loop. This means that when the magnetic field around a conductor changes, it generates an electric current. The strength of the induced EMF is directly proportional to the rate of change of the magnetic field. This principle is fundamental in many electrical devices, such as electric generators and transformers. Faraday's law is a key concept in electromagnetism, helping to explain how electricity can be generated from motion and how energy can be transferred efficiently in electrical systems.