Why start the discussion of energy conversion devices with a discussion of capacitors? Capacitors are familiar to electrical engineers, and they are energy storage devices. How do capacitors work? What are the components of a capacitor? What materials are capacitors made out of? What are the differences between different types of capacitors such as mica capacitors and electrolytic capacitors? In an introductory circuits course, a capacitor is a device where the relationship between the current $$i$$ and voltage $$v$$ is given by $i = C \frac {dv} {dt}$
and the capacitance $$C$$ is just a constant. The only difference between one capacitor and another is the capacitance value. In order to answer these questions further, we need to go beyond this model. Through this study, we will gain insights into piezoelectric devices, pyroelectric devices, and electro-optic devices too.