I am choosing topic 5, Capacitor Advantages and Disadvantages. The two main types of capacitors to be discussed will be electrolytic and ceramic capacitors. The electrolytic capacitor is a polarized capacitor meaning that it has a positive and negative terminal. Therefore, proper orientation in the circuit is necessary. Ceramic capacitors are non-polarized meaning that they can be connected in either orientation in the circuit. One type of electrolytic capacitor is formed by two aluminum electrodes in an electrolyte of borax, phosphate, or carbonate. Between the two aluminum strips, absorbent gauze soaks up the electrolyte to provide the required electrolysis that produces an oxide film. Ceramic capacitors are made from earth fired under extreme heat. Sometimes titanium dioxide or one of several types of silicates is used for the dielectric. Silver is often used on both sides of the dielectric to form the plates of the capacitor. Probably the main advantage of ceramic capacitors is that they can be manufactured for very high values of dielectric constants (k) and provide a wide range of capacitance (1pf to 1 microfarad).
Except for electrolytics, ceramic capacitors and most other capacitors do not wear out while being stored on the shelf. However, electrolytics should be used fresh from the factory because of the wet electrolyte that usually dries up over a period of time. Also, the capacitor value changes drastically as the electrolyte dries up. However, the ceramic capacitor value may change only 10-15% during the first year of storage as the ceramic material relaxes. After a few years of service, if the electrolyte dries up, electrolytics usually become partially open and should be replaced because much of the capacitor action is gone. Temperature and age deterioration can also cause many capacitors to become shorted. This is even more common with electrolytics.
Dielectric absorption is the inability of a capacitor to completely discharge to zero. This phenomenon is commonly called “battery action” or “capacitor memory” due to the dielectric retaining a charge after it is supposedly discharged. Electrolytics have more of this characteristic than most other capacitors.
Equivalent Series Resistance (ESR) is also higher in electrolytics than other types of capacitors. This resistive effect is caused by the fact that charge and discharge action cannot be followed instantaneously. Probably, the main advantage of electrolytic capacitor is its cost effectiveness in providing the highest capacitance in the smallest possible space. One major area of concern for electrolytics is that they can be instantly destroyed or burned and cause an explosion if connected in the wrong orientation in the circuit.
Douglas
References
Floyd, T. L., Buchla, D. M. (20190225). Principles of Electric Circuits, 10th Edition. [[VitalSource Bookshelf version]]. Retrieved from vbk://9780134880068
Schultz, M.E. and Grob, B. (2016) Grob’s Basic Electronics. 12th ed. , New York, NY: McGraw-Hill Education.
