Capacitors are electronic components that function similarly to batteries. The similarity that they share with batteries is that they can store energy but, overall, a capacitor is a much simpler device than a battery.
A capacitor, on the inside, consists of metal plates separated by a dielectric, which is a substance that functions as an insulator. There are multiple different types of insulators utilized in capacitors. Various ceramics are utilized in many instances, glass is utilized in some capacitors and other materials, such as Mylar, are utilized, as well. In simple capacitors, air is sometimes the insulator between the plates.
The capacitor functions best when there is a very narrow separation between the conductors. The conductors are typically referred to as plates, though they may not actually be flat and stacked parallel on top of each other in a capacitor.
While capacitors are very useful devices, they do have some characteristic imperfections in them that need to be accounted for when choosing one of these devices for an electronic application. For example, capacitors oftentimes change in terms of their capacitance and other properties as they age. This has to be taken into account, as it is inevitable that the capacitor will stray outside of its normal operating performance as the device gets older. Additionally, temperature affects some types of capacitors significantly and that can change the performance of the devices.
One of the most common uses of capacitors is in radios. Radio tuners utilize capacitors to allow the device to be tuned into different frequencies. Other common devices for capacitors include use in power supplies. Capacitors are able to smooth out currents flowing through a circuit, and this makes them perfect solutions to providing a stable, steady source of power for a wide range of devices, including the power supplies utilized in experimentation and engineering.
Large capacitors are used in applications in power grids. As they do in other applications, these capacitors function to make certain that the voltage across these systems remains stable and predictable and they smooth out spikes in the system.