This document discusses several electrical and mechanical components: 1. Transformers transfer electrical power from one alternating current circuit to another through mutual induction without electrical contact. The changing magnetic flux in the primary coil induces an EMF in the secondary coil. 2. Induction motors operate on the same principle as transformers, with the stator acting as the primary and the rotor as the secondary. 3. Photovoltaic solar cells directly convert sunlight into DC electricity through a structure that supplies voltage and current to loads like batteries. 4. The piezoelectric effect converts mechanical pressure on crystals into an electric voltage or vice versa through crystal deformation.