Flame rectification is a phenomenon in which a
flame
A flame () is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction made in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density, they are then considered plasm ...
can act as an electrical
rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction.
The process is known as ''rectification'', since it "straightens" t ...
. The effect is commonly described as being caused by the greater mobility of
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
s relative to that of positive
ion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s within the flame,
and the asymmetric nature of the
electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...
s used to detect the phenomenon.
This effect is used by rectification flame sensors to detect the presence of flame.
[ The rectifying effect of the flame on an AC voltage allows the presence of flame to be distinguished from a resistive leakage path.
One experimental study suggested that the effect is caused by the ionization process occurring mostly at the base of the flame, making it more difficult for the electrode further from the base of the flame to attract positive ions from the burner,]
See also
* Flame detection
* Flame supervision device
References
{{reflist
External links
A video of a flame being used as a rectifier in a simple AM radio
Plasma technology and applications