A typical microwave oven has an optoelectronic device, called, magneton which holds a thermionic electron emitter (cathode) and an electron collector (anode), both fitted into an evacuated cylinder under a magnetic field. The ejected and accelerating electrons take a curved path to reach the destination (anode) while transmitting microwave radiation. It is this radiation that is dispersed into the cooking compartment by appropriate electromechanical design.
Substances, with polar molecules such as water, alcohols, oils, etc, absorb microwave radiation to elevate the rotational movements of their molecules. When foodstuffs to be cooked by microwave oven are kept in this kind of kettle, the majority of the microwave power reaches the water and tends to hasten the molecular rotations. But, owing to the matrix and intermolecular ligaments, water molecules experience restricted rotation and dissipate the absorbed microwave optical energy into heat out of molecular frustrations. It is this heat that causes faster cooking of the food stuffs.
When we heat a cup of water alone in a microwave oven, the water gets all the microwave energy and becomes hot.
Though designed to distribute the microwave energy homogeneously (isotropic) into the cooking compartment, the top regions, usually receive a slight excess.
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A plasma is a hot ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged electrons. The characteristics of plasmas are significantly different from those of ordinary neutral gases so that plasmas are considered a distinct "fourth state of matter." For example, because plasmas are made up of electrically charged particles, they are strongly influenced by electric and magnetic fields while neutral gases are not. An example of such influence is the trapping of energetic charged particles along geomagnetic field lines to form the Van Allen radiation belts.
ReplyDeleteIn addition to externally imposed fields, such as the Earth's magnetic field or the interplanetary magnetic field, the plasma is acted upon by electric and magnetic fields created within the plasma itself through localized charge concentrations and electric currents that result from the differential motion of the ions and electrons. The forces exerted by these fields on the charged particles that make up the plasma act over long distances and impart to the particles' behavior a coherent, collective quality that neutral gases do not display. (Despite the existence of localized charge concentrations and electric potentials, a plasma is electrically "quasi-neutral," because, in aggregate, there are approximately equal numbers of positively and negatively charged particles distributed so that their charges cancel.)
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ReplyDeleteWHAT IS GAS PLASMA AND SHOULD YOU CARE?
ReplyDeleteBy: Stephen L. Kaplan
ABSTRACT
Plasma surface treatment of plastics is definitely not new, nor is it commonplace. What is a plasma and what can it do is the subject of the following paper. A plasma is an excited gas, not unlike the aurora borealis. The excited particles that comprise the plasma bombard materials placed within their environment causing permanent change to their surface properties. By the judicious selection of process gas(es) and process parameters, the surface can be reengineered to fit specific needs. This paper presents quantitative analytical data on the chemical changes to the surface of polyethylene subjected to a plasma.
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