Concepts
Key concepts to acquire
Last updated
Key concepts to acquire
Last updated
MEMS
Micro-Electro-Mechanical-Systems (MEMS) is at the core of this structure. The article by Bao and Wang (1996) defines the MEMS [4] as
one that consists of a micromachine and micro- electronics, where the micromachines are controlled by microelectronics
and is that largely enables the microcontrol of kinetic energy and largely into a mechanical system; however, its principle remains such that it will use 'regional selectivity' adopted and machined with microcontrollers.
Thermodynamics
Joule heating (ohmic heating, resistive heating): When a current flows through an electrical conductor, it creates heat. This resistive heating is the result of “friction,” as created by microscopic phenomena such as collisions involving the charge carriers (usually electrons); Joule heating is also known for a flash pasteurization process that allows the liquid matrix and particulates to encapsulate heat thereby a quick sterile product is produced. It is a type of external heating [1]. Direct current flows in that:
In pure resistor, power is equivalent to the product of voltage and current, and when pure resistor is connected to sinusoidal voltage, there is the current flowing that varies in proportion to supply voltage and are 'in-phase'. The phase difference between voltage waveform and current waveform is 0 and so cos0 will equal to 1.
The voltage difference multiplied by the current is the ultimate power (W) and it can be re-written as P = IV = I^2R.
Alternating current accentuates that this can be time-specific: P(t) = I(t)V(t) when t is time.
Resistive heating is used directly in incandescent light bulbs, irons, electric hotplate, and so on.
However, we must consider heat efficiency; their purpose is to transmit energy, not to dissipate it; the energy converted to heat along the way is, in effect, lost (thus the term resistive losses) [2].
* Induction heating: Is when an electromagnetic field is realized, with heat transfer through an inductor while coiling up and melt conductive materials (i.e. metal) and it is fast. Induction heating need not external heat source nor direct contact. It operates with electromagnet and electronic oscillator with high frequency alternating current. Mechanisms such as brazing, melting, furnacing, welding, and induction cooking are enabled by this. It is a type of internal heating.
Thermoelectric Effect
Largely thermoelectricity is a concept to convert electrical energy to heat energy and vice versa that can work in two ways. It embraces the two concepts that are enabled by multiple scientists and nominated after their names.
Seebeck
Operates as two points of electircally conductive matieral induces a temperature between the distances. Seebeck observed the electromotive force, whereby the comapss needle will swirl as heat is applied at the intersection of two different materials of metals. With the Seebek coeffecient (S) that will be the thermopower, and temperature gradient (∇T) we can create an electromotive field as:
Peltier
While the seeback circuit would enable the heat energy to be converted into electrical energy, the Peltier effect will convert electric current into an active cooling energy whereas the insulating bottom layer will change the difference between two currents into amplified energy [3]. Its effect is amplified by preventing the heat loss and dissipating heat with heat sink or a cooling fan for underneath. It is a basis for refrigerator where it does not require cooling machine to really 'cool' the interior. Modern day Peltier modules have P and N-type semi-conductors in between the two plates in that it will cycle the currents from one direction to another. By reversing the polarity of the supply voltage, it is possible to reverse the "hot and cold" sides of the module. We can see the difference via this image below:
Thermocouples calculate the unknown temperatures of two sides, and since the voltage at the loose ends of wires is dependent on this unknow temperature, it can be used as a thermometer and thermosensor, enabling the knowledge between S and T curves of two materials.
** PTC Heating: A positive-temperature-coefficient heating element is also a concept that is worth exploring, as it is largely a resistive heater in which its resistance increases as it self-regulates with temperature. Here, a PTC heating element is great for heating small regions and as a thermistor (a type of resistor that has resistance to temperature) as well.
References:
[1] Electronics Tutorials. (n.d.). Power in AC circuits. Retrieved October 30, 2024, from https://www.electronics-tutorials.ws/accircuits/power-in-ac-circuits.html
[2] Electrical Engineering Portal. (n.d.). Resistive heating explained in detail. Retrieved October 30, 2024, from https://electrical-engineering-portal.com/resistive-heating-explained-in-details
[3] ScienceDirect. (n.d.). Peltier effect. Retrieved October 30, 2024, from https://www.sciencedirect.com/topics/chemistry/peltier-effect
[4] Zhang, Y., & Chen, X. (1996). Thermoelectric properties of Bismuth Telluride thin films. Journal of Materials Science Letters, 15(11), 1015-1017. https://doi.org/10.1016/0924-4247(96)01274-5
[5] Electronic Tutorials. (2016). Sinusoidal voltage waveform. Retrieved October 30, 2024.
[6] Tritt, T. M. (2000). Peltier thermoelectric couple. In Encyclopedia of materials: Science and technology (pp. 7251-7256). Elsevier.
